SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY / NUMBER 28 
Water Current Meters 
IN THE SMITHSONIAN COLLECTIONS OF THE 
NATIONAL MUSEUM OF HISTORY AND TECHNOLOGY 
Arthur H. Crazier 
ISSUED 
EEC 3 0 1974 
SMITHSONIAN INSTITUTION PRESS 
City of Washington 
1974 
A B S T R A C T 
Frazier, Arthur H. Water Current Meters in the Smithsonian Collections of the 
National Museum of History and Technology. Smithsonian Studies in History and 
Technology, number 28, 95 pages, 94 figures, 1974.?Water current meters are the 
basic instruments used in connection with stream gaging, the art of measuring and 
maintaining a continuous record of the volume, in cubic feet (or cubic meters) per 
second, of water flowing in rivers. The history of both that art and these instruments 
forms a large part of this study. The contributions of men like Marcus Vitruvius, 
Hero of Alexandria, Leonardo da Vinci, Benedetto Castelli, Sir Isaac Newton, and a 
large group of eminent modern hydrographers are discussed. 
Special attention is given to the type of current meters built for use on rivers 
such as those in the collection of the Smithsonian Institution. It does not include 
meters of the type featured in the collection at the Institut Oceanographique, Musee 
de Monaco, most of which were developed especially for measuring ocean currents. 
Whenever possible, the men responsible for introducing each new design are also 
discussed. 
OFFICIAL PUBLICATION DATE is handstamped in a limited number of initial copies and is re?
corded in the Institution's annual report, Smithsonian Year. SI PRESS NUMBER 4968. 
Library of Congress Cataloging in Publication Data 
Frazier, Arthur H. 
Water current meters in the Smithsonian collections of the National Museum of History and 
Technology. 
(Smithsonian studies in history and technology, no. 28.) 
Supt. of Docs, no.: SI 1.28:28. 
Bibliography: p. 
1. Water current meters?History. 2. U. S. Museum of History and Technology. I. Title. 
II . Series. Smithsonian Institution. Smithsonian studies in history and technology, no. 28. 
TC175.F76 551.4'83'028 74-5425 
For sale by the Superintendent of Documents, U.S. Government Printing Office 
Washington, D.C. 20402 - Price $2.05 
Stock Number 4701-00116 
Preface 
There has always been a close and cordial relationship between the Geological 
Survey and the Smithsonian Institution. Clarence King, the Survey's first director 
(1879-1881), received Smithsonian aid for his famous U.S. Geological Explora?
tion of the Fortieth Parallel?the first systematic reconnaissance of that vast un?
mapped area of this country between the 105th and 120th meridian. John Wesley 
Powell, the Survey's second director, whose two trips through the Colorado Canyon 
brought him everlasting fame, conducted several investigations between 1871 and 
1874 with funds from Congressional appropriations stipulating that the work be 
performed "under the direction of the Smithsonian Institution." After those (and 
later) investigations were completed, the Smithsonian Institution established a 
Bureau of American Ethnology, with Powell in charge thereof. Just one year later, 
he assumed the directorship of the Geological Survey and for many years handled 
both positions at his office in the Smithsonian Institution building. The third director 
of the Geological Survey was Charles Doolittle Walcott who, after serving from 1894 
to 1907 as director of the Survey, became the Secretary of the Smithsonian, a position 
which he held until his death in 1927. For about one year before receiving the 
Smithsonian appointment, he divided his time between those two organizations, 
serving then as the Acting Assistant Secretary of the Smithsonian in Charge of the 
National Museum. 
Much of the information in this study was made available to the writer while 
employed in the Water Resources Division of the United States Geological Survey, 
an organization where current meters are as essential to its field engineers as a trowel 
is to a mason, or a plow is to a farmer. To the late Nathan C. Grover, Carl G. Paul?
sen, and John C. Hoyt, and to many of those others still living who guided my work in 
that agency and who encouraged my desire to delve into the history of current meters 
and stream-gaging methods, I am deeply grateful. 
John Clayton Hoyt (1874-1946) was employed by the Geological Survey in 
1902, and served that agency until his retirement in 1944. During parts of those 
42 years, he held the positions of Assistant Chief Hydrographer and Chief, Surface 
Water Division. Among his many interests was the improvement of current meters 
and the preservation of many of the early models. His early association with Walcott 
was conceivably a major influence in his having transferred several of those early 
meters (as soon as they achieved historical significance) to the Smithsonian Institu?
tion. Among them were several of the meters that had been used in the late 1880s 
by the U.S. Irrigation Survey, and the original models of both the Large and the 
Small Price current meters, which form the very foundation of the Smithsonian's 
fine collection. For John Hoyt's personal friendship and shining example, I have a 
deep sense of gratitude. 
I also wish to express my gratitude for the help given me by staff members of 
the Library of Congress, the Library of the universities of Wisconsin, Ohio State, and 
especially Iowa State, the latter of which houses the fine " H H T " collection spon?
sored by Dr. Hunter Rouse, who provided much valuable data for this study. 
For much of the information regarding the early stream-gaging activities in 
foreign lands, I am particularly indebted to the late Professor Steponas Kolupaila 
of Notre Dame University, and to Dr. Carlo Zammattio of Trieste, Italy. For much 
iii 
of the information regarding William Gunn Price and the early Price current meters, 
I am equally indebted to his own grandson, W. G. Price of New Cuyama, California, 
and to the late Charles E. Smart who, for many years had been Chairman of the 
Board in the W. & L. E. Gurley firm of Troy, New York. 
My sincere thanks are due to present members of the staff of the National Mu?
seum of History and Technology, Smithsonian Institution, in which the current meter 
collection is presently housed, and especially to its former director, Robert P. Mul-
thauf, who encouraged me to undertake this study; to Jack Goodwin and Charles 
Berger of the museum's library, who helped me locate many of the books for which 
I felt a need; to George Norton, who arranged that I be furnished with photographs 
of the meters in the collection; and finally to Jon Eklund, who helped in so many 
ways while I was preparing this study. 
IV 
Contents 
Page 
Preface . . . . . . . . iii 
Introduction . . . . . . . . 1 
Ancient Concepts . . . 2 
Emergence of Modern Hydrometric Methods . . . . . . . 6 
Q = A vs Q = AV . . . . . 6 
Free Floats . . . . . . . . . . . 8 
Tethered Floats . . . . . . . . 1 5 
Paddles . . . . . . 18 
Paddle Wheels . . 21 
European Contributions . . . . . 22 
American Innovations. 28 
Tubing Applications . 33 
The Pitot Tube . . . . 33 
The Bentzel Velocity Tube . . . . . . 3 5 
The Venturi Tube . . . . . . . ? . . . 37 
The Longitude Contest . . . . . . . . . 41 
De Saumarez' Ships' Logs . . . . . 41 
The Log with a Vertical Axis . . . . . . . . . 4 1 
The Log with a Horizontal Axis . 43 
Administrative Strategy, 1716 Style . . . . . 46 
Horizontal-Axis Meters . . . . . . . . . 48 
Early European Developments . . . . . 48 
Robert Hooke 48 
Reinhard Woltman . . . . . . . . . . 49 
Julien John Revy . . . . . . . 5 0 
Joseph Saxton . . . . . 5 1 
The Baumgarten Meter . 56 
Other American Models . . 63 
Hall's Current Meters . 6 3 
The Haskell Current Meter . . . . . . . . . 64 
U.S. Irrigation Survey Models . . . . . 66 
Other European Developments 67 
.Moore's Current Meter . . . . ? . . . . . 6 7 
The Firm of A. Ott 68 
Steponas Kolupaila . . . 69 
Vertical-Axis Meters . . . . . . . . 72 
The Henry Meter ? . 73 
The Ellis Meters . . 74 
The Nettleton Meter 75 
The Price Meters 78 
Notes . 8 7 
Literature Cited . . . . . . 88 
[ndex . . . . . . . . 92 
Water Current Meters 
Arthur H. Jrazier 
I N T R O D U C T I O N 
A primary purpose of this study is to present a 
catalog of the water current meters in the Smith?
sonian Institution's National Museum of History and 
Technology, the largest collection of its kind in the 
world. It is also intended to present background in?
formation that will provide the reader with an under?
standing of where each current meter in the collec?
tion (and its designer) fits into the general historical 
setting relative to such instruments. The illustrations 
of current meters, for which accession numbers 
( N M H T ) are noted, represent the present collection 
of such instruments in the Smithsonian Institution. 
Water current meters (referred to hereafter as 
"current meters" or simply "meters") are instruments 
used for evaluating the amount and velocity of water 
at one or more points in a flowing stream at any 
particular moment in time. The amount of water is 
measured in cubic feet per second, whereas the vel?
ocity is determined in feet per second. 
In America, the United States Geological Survey 
publishes in its Water-Supply Papers, the daily aver?
ages of the flow at almost 9000 "gaging stations" 
throughout all of the States. The following are just 
a few of the important uses made of such streamflow 
records: 
DAMS.?Dams are built for water-supply purposes, 
hydroelectric power, flood control, irrigation, naviga?
tion improvement, recreation lakes, and a host of 
other purposes. In each instance, a careful study of 
all pertinent streamflow records must be made well 
Arthur H. Frazier, 3636 Sixteenth Street, N. W'., Washing-
:on, D.C. 20010. Honorary Research Associate, Smithsonian 
Institution. 
in advance of any construction work to determine 
whether the drainage area above the selected site 
would yield a sufficient amount of water to accom?
plish the purpose for which the dam is intended, and 
to determine the amount of water that is likely to 
flow there under the maximum flood conditions. In?
adequate spillway capacities constitute the major 
causes of dam failures. Therefore, a vital requirement 
in the design of any proposed dam is that its spillway 
capacity will be adequate to accommodate the largest 
probable flood. 
LITIGATIONS.?Litigations involving uses of water 
have occurred ever since the advent of written history. 
In A History of Technology edited by Charles A. Sin?
ger, et al., one finds that the words "rivers" and "ri?
vals" stem from the same source. "That very word 'ri?
vals' in Roman law denoted those who shared the 
water of a rivus, or irrigating channel; it thus implies 
jealously guarded rights and frequent quarrels." 1 
In modern societies, perhaps the most equitable 
method yet devised for settling such disputes has been 
by means of court decisions that allot certain amounts 
or proportions of the available water to each litigant 
who has a legitimate right to it. Water masters are 
appointed to carry out these court orders. In almost 
all instances the masters base the distribution on dis?
charge data procured through the use of current 
meters. Thus again we see that the reliable evaluation 
of discharge data is essential. 
PUBLIC HEALTH.?Today streams are often pol?
luted by untreated sewage, manufacturing wastes, 
modern detergents, and dangerous chemicals, with a 
consequent destruction of fish and wild life. A large 
SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 
percentage of attractive recreational waters and city 
water supplies have consequently been withdrawn 
from public use. Conservation officials and public 
health officials at all levels of government are deeply 
concerned about those conditions, particularly during 
periods of drought, when streams are low and the con?
sequent percentage of pollution is exceptionally high. 
Streamflow records indicating the approach, arrival, 
intensity, and passage of these periods provide im?
portant information on which such officials can make 
appropriate administrative decisions. 
HIGHWAY BRIDGES AND CULVERTS.?The intel?
ligent design of bridges and culverts for the vast net?
work of highways across the nation depends on the 
availability and adequacy of streamflow records. 
Without such records, these structures might be built 
too large, resulting in excessive cost, or too small, 
thereby endangering the road in times of severe floods. 
Although this list could be greatly expanded, these 
examples are sufficient to indicate the importance of 
such records in relation to modern engineering and 
humanitarian problems.2 
ANCIENT CONCEPTS 
Although legends and archeological investigations 
have extended our knowledge of man's involvement 
with flowing water farther into the past than has 
written history, only two written records about it have 
survived from ancient times. The first is in Section 53 
of the famous Code of Hammurabi (Figure 1) re?
ported in Webster's New International Dictionary 
(2nd edition) to have been written between 1955 and 
1913 B.C. It contains the following regulation: 
If anyone be too lazy to keep his dam in proper condition, 
and does not keep it so: If then, the dam breaks and all the 
fields are flooded, then shall he in whose dam the break 
occurred be sold for money and the money shall replace the 
corn which he has caused to be ruined.3 
The second of those records was found among 
the ruins of a temple which the Pharoah Akhenaten 
(the older brother of Tutankhamun) built in about 
1400 B.C. at Tell 'Armarna, Egypt, in honor of the 
god Ra who he had intended would replace Egypt's 
Pantheon. It consisted of the following inscription 
proclaiming that his new faith would endure 
Until the swan grows black 
And the Raven becomes white: 
Until the Mountains rise up and walk, 
And the waters flow uphill fitalics added].4 
Ditches were the earliest structures devised for the 
control of water on the great flood plains of rivers like 
the Nile, Hwang-Ho (Yellow), Tigris-Eurphrates, 
and Indus. They served two purposes: first, to drain 
off the excess water after floods, and second, to ir-
FIGURE 1.?Portion of the Code of Hammurabi. 
(Courtesy of the Louvre, Paris.) 
rigate the crops during the long dry periods. There 
were, however, other locations, namely the oases in 
deserts, where such ditches served only the latter pur?
pose, i.e., irrigation. 
NUMBER 28 
It is of interest to note in this connection that many 
desert communities developed essentially the same type 
of water clock for the sole purpose of limiting the 
amount of water that each of the farmers in those 
communities were allowed to take from the irrigation 
ditches.5 The method still in use at the Oasis Ghad-
ames in Western Libya, provides an excellent example 
of one of those clocks and of the procedures that were 
followed there for the past thirty or more centuries: 
At the spring "Ain El Fras" at the Oasis Ghadames, the 
amount of time the landowners are permitted to draw water 
for their gardens from the irrigation ditch, has been con?
trolled during the past 3000 years or more by the methods 
shown here [Figure 21. At the local marketplace (quite some 
distance from the ditch) is a shallow well presided over by 
an attendant who lowers a bucket into the well until it be?
comes filled with water. Then he raises it, hangs it onto a 
nearby peg while he makes a record thereof by tying a knot 
into a fiber from the bark of a palm tree. The water drains 
back into the well through a hole in the bottom of the 
FIGURE 2.?Oasis Ghadames: a, c, the "water clock" at the market 
place; b, the reservoir at the spring, Ain el Fras; d, gardeners divert?
ing the irrigation water. (From Schaack, "Vergangenheit.") 
SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 
bucket, and when empty, the procedure is repeated (over and 
over again day and night, each cycle requiring about five 
minutes). Each landowner in turn is allowed to divert into 
his garden, water from the irrigation ditch for the time it 
takes for the bucket to be filled and emptied a certain num?
ber of cycles depending upon the pioportion of land he owns 
in the area. He must be ready to open his water gate at the 
beginning of the particular series of cycles that are allotted 
to him, and upon the completion of that series, he must close 
his gate and allow the water to pass on to the next land?
owner in line, who will be waiting his turn. Although mod?
ern clocks would accomplish the same results with fewer 
complications, there does not seem to be any inclination to 
change this ancient practice.6 
One observation regarding this desert practice mer?
its particular mention here. It is that from time im?
memorial, these people were acquainted with one of 
the basic concepts in hydraulics, namely that the 
amount of discharge taking place in any irrigation 
ditch (or in any stream of water) is a function of 
time. 
Much more technologically advanced structures de?
vised for the control of water are the famous Roman 
aqueducts. Although Sennacherib's aqueduct at Jer-
wan in northern Iraq 7 is perhaps 400 years older 
than the first of the Roman aqueducts and ranks 
among the earliest of such structures, the Roman 
aqueducts (begun in about 300 B.C.) are of the great?
er interest here because of the water-measuring facil?
ity, the quinaria, which is associated with them. 
The quinaria is a unit of measurement, by which 
water is apportioned. Apparently first introduced by 
the Romans, it was defined by a circular area about 
VA "digits" in diameter. Sextus Julius Frontinus, the 
Water Commissioner of Rome in about A.D. 97 men?
tioned its origins in his writings: 
According to those who ascribe it to Vitruvius and the 
plumbers, it [the quinaria] took its name from the circum?
stance that a flat sheet of lead, five digits wide, made up 
into a round pipe, will form this adjutage.9 
By "adjutage," Frontinus had reference to the pipes 
that were inserted through the walls of Rome's sup?
ply reservoirs through which water was delivered to 
the conduits of the various consumers. Numerous 
sizes eventually became available, with each adjutage 
stamped with the number of quinariae present in their 
respective cross-sections. The consumer, at regular 
intervals, paid to the State a sum computed by mul?
tiplying the unit price of a quinaria by the number 
stamped on his adjutage. 
No serious attention was paid to the elevations at 
which these adjutages were located in the walls of 
the reservoirs, nor to any other inequities which could 
be found with the system. Nevertheless, this is one 
of the earliest known methods of measuring directly 
the flow of water. This same erroneous technique was 
also applied to measuring the flow in open channels. 
The water master merely measured the wetted cross-
sectional area of the channel to determine the number 
of quinariae. He was not concerned as to whether the 
location of that measurement was at a narrow and 
shallow, or wide and deep place in the channel. Fron?
tinus himself made a number of such measurements 
to determine whether the number of quinariae flow?
ing into the reservoirs corresponded with the number 
of quinariae delivered to the consumers. When he 
found that there was an enormous discrepancy, he 
began to question the honesty of his deputies rather 
than to question the validity of his stream-gaging 
methods.9 
The circumstances just described characterize the 
state of the art of stream gaging from ancient times 
forward. Mistakenly based on the concept that the 
discharge of water is equal to the wetted cross-section 
of an open or closed channel ( Q = A) , the concept of 
the discharge of streams as a function of time was not 
considered. There was at that time, however, one 
person who took exception to the current theory? 
Flero of Alexandria. 
Hero of Alexandria was a Greek mathematician 
and mechanician of the first century A.D. His accom?
plishments, too numerous to list here, are so impres?
sive that one school of thought has contended that he, 
like Nostradamus, was a mythical character who had 
been credited with having conceived almost every ex?
traordinary mechanical device then existing. In any 
event, in his book, Dioptra, he described a way to 
measure the discharge of a spring, which is now 
known as the volumetric method (Figure 3) . This 
method which has never been surpassed in accuracy, 
is based on the concept that the area of a channel 
multiplied by the velocity of flow equals the amount 
of water passing a given point at a particular moment 
in time. 
Given a spring: To determine its flow, that is, the quantity 
of water which it delivers . . . . 
Now, it is necessary to block in all the water of the spring 
so that none of it runs off at any point, and to construct out 
of lead, a trough having a rectangular shape. Care should be 
taken to make its dimensions considerably greater than those 
of the stream of water. It should then be installed at a 
NUMBER 28 
FIGURE 3?The world's first valid streamflow measurement as described by Hero of Alexandria, 
first century A.D. (Drawn by A. H. Frazier.) 
place such that the water from the spring will all flow 
through it That water will cover a portion of the 
cross-section of the trough at its mouth. Let this portion be 
for example, 2 digits in height. Now suppose that the width 
of the trough is 6 digits; 6 X 2 = 12. Thus the flow of 
the spring is 12 1 square] digits. 
It is to be noted that in order to determine how much 
water the spring supplies, it is not sufficient to merely find 
the area of the cross-section of the flow, which in this case 
we say is 12 [square I digits. It is also necessary to find the 
speed of the flow. The swifter the flow, the more water is 
supplied by the spring, and the slower it is, the less. One 
should therefore dig a reservoir to receive the flow, and note 
with the help of a sun dial how much water flows into that 
reservoir in a given time, and thus calculate how much will 
flow in a day. It is therefore unnecesary to measure the area 
of the cross-section of the stream, for the amount of water 
will become clear from the measurement of the time. I0 
I Italics added.] 
Although his technique is primitive, in the forego?
ing description will be found all of the elements that 
enter into the most fundamental modern equation 
pertaining to streamflow namely Q = AV (i.e., the 
quantity of discharge is equal to the wetted cross-
sectional area multiplied by the average velocity of the 
stream). This equation applies equally well to the 
movement of avalanches, mud-slides, and any number 
of similar phenomena. Unfortunately, Hero's concept 
and methodology were apparently too far ahead of 
his time. Little attention was paid to them until after 
the Dark Ages. When those who ultimately adopted 
Hero's volumetric method and applied it to the de?
sign of equipment in modern hydraulic laboratories, 
they probably did so without realizing that Hero had 
conceived the idea as much as 1900 years earlier. 
SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 
EMERGENCE OF MODERN HYDROMETRIC METHODS 
Q = A vs Q = AV 
As previously mentioned, the prevailing method of 
measuring streamflow in ancient Rome persisted well 
into modern times. As noted, it consisted merely of 
measuring the wetted cross-section of a stream and 
accepting the area thus obtained for the figure that 
represented the discharge. The calculation was based 
simply on the equation, Q = A (quantity equals the 
cross-sectional area) . On Christmas day, 1598, when 
a great flood occurred on the Tiber River at Rome, 
one Giovan Fontana was still using that equation and 
technique when he undertook the task of determining 
the maximum discharge that occurred during that 
flood. 
Fontana waited for the streams that had contrib?
uted to the flood to return to their normal flows. Start?
ing with the Tiber River near Perugia, some 80 miles 
north of Rome, and also for all of the streams enter?
ing the Tiber between that point and Rome, he 
measured their wetted cross-sections. At the same 
time, he determined from the highwater marks that 
remained alongside of those sections the probable 
areas that the water had occupied when the river and 
its tributaries had been in flood. 
The water in the Tiber, at the Castello di Corbara, nearly 
a mile above the confluence with the Paglia River, is ordin?
arily 299 palms wide, and has an average depth of 14'/2 
palms. At the time of the flood, its width was 377Vi palms, 
and it had risen 36 palms. The increase amounted to 135 
[square] canna and 90 [square] palms." 
After computing the amounts which each tributary 
(including the upper end of the main river) had in?
creased on that occasion, Fontana added them all 
together, and concluded that "the measurements of 
the Christmas flood show that the area above Rome 
contributed into the Tiber (at Rome) 500 [square] 
canna and 9 [square] palms more than the river or?
dinarily carries." 12 
It will be recognized that the method Fontana had 
used for gaging these streams was identical to that 
which Frontinus had used back in A.D. 97 when 
measuring the streams which contributed water to the 
Roman aqueducts. To modern hydraulic engineers, 
who are accustomed to expressing river discharge in 
terms of cubic feet per second, neither Frontinus' nor 
Fontana's results would have any quantitative mean?
ing. In fact, they even failed to convey any meaning 
to one of Fontana's illustrious contemporaries, Bene?
detto Castelli (1577?-1644) (Figure 4 ) . In a book 
entitled Delia Misura DelVAcque Correnti [The Men?
suration of Running Waters], first published in 1628 
and translated into English in 1661 by Salusbury,13 
Castelli completely refuted the validity of the Q = A 
equation. 
A large portion of Castelli's book was devoted to 
explaining the nature of velocity and how it affects 
the flow in rivers, a phenomenon that both Frontinus 
and Fontana had not considered. Castelli's work re?
ceived high acclaim and recognition. Galileo, for 
example, referred to it as a "golden book," and even 
today there are many who refer to Castelli as the 
"Father of Modern Hydrodynamics." 14 
FIGURE 4.?Benedetto Castelli. 
(Courtesy of Hunter Rouse.) 
NUMBER 28 
The date and place of Castelli's birth is somewhat 
in doubt. Gillispie gives it as 1578, although Poggen-
dorff and several earlier authorities noted it as 1577.15 
Although most authorities claim that he was born in 
Brescia in northern Italy at the foothills of the Alps, 
the earliest biographical sketch of him, published in 
1661 by Thomas Salusbury, states that he had been 
born "near Lake Thrasimenus (Trasimeno), where 
Hannibal overthrew the Roman Legions." 1G Lake 
Trasimeno is near Perugia, close to the upper end of 
the reach of the Tiber River where Fontana had 
measured that devastating flood of 1598. 
Be that as it may. Castelli's parents entered him 
into the Order of Black Friars while he was quite 
young, and he became one of the monks (and later 
an abbot) in the Benedictine Order at Monte Casino. 
The Monte Casino Monastery was located on a high 
promontory about 87 miles south of Rome. It was 
destroyed by bombs during World War II , but was 
subsequently rebuilt at a somewhat lower level. With?
in this monastery the previously mentioned report on 
the Roman aqueducts by Frontinus had been copied 
and preserved. Castelli had doubtless read it there 
because in his book, he strongly repudiated the Q = A 
concept of making streamflow measurements as des?
cribed therein. 
While at Monte Casino, Castelli had become an 
outstanding student of mathematics, a talent that 
brought him to the attention of the great Galileo. It 
is known that as early as 1603 Castelli had watched 
Galileo demonstrate the principle of his "thermiscope" 
during a lecture at the University of Padua, but ap?
parently it was not until about 1611 that the two had 
become closely associated. Castelli moved to Florence 
in April 1611 to be with Galileo, where he became 
one of the greatest of Galileo's pupils.17 When Galileo 
made his famous discovery regarding sun spots, it was 
Castelli who devised telescopic techniques for plotting 
their movements, which proved Galileo's observations 
thereon to be correct. Furthermore, when Galileo ran 
into trouble with the powerful ecclesiastical forces (as 
he did on several occasions), Castelli was always the 
first to advise and defend him. On the other hand, 
Galileo consistently and lavishly praised the accom?
plishments of his protege. At his recommendation, 
Castelli became professor of mathematics at Pisa, a 
chair that he occupied from 1613 to 1616.18 
While teaching at Pisa, Castelli became interested 
in the motion of water in rivers. Pisa is located on 
the Arno, an extremely unruly river that is subject 
to frequent and devastating floods. Attempts to con?
trol the river can be traced as far back as the year 
A.D. 1077. The best engineering talent in Italy had 
been brought to bear in that effort. About 100 years 
prior to Castelli's arrival at Pisa, Leonardo da Vinci, 
the greatest engineer of the Renaissance had worked 
on that project. Of his work thereon, General William 
Barclay Parsons has expressed the following views: 
In the development of his new design, Leonardo gave the 
most advanced exhibition of creative engineering imagina?
tion that so far had been conceived, and it is doubtful, when 
his complete lack of precedent and of accurate knowledge 
are compared with the wealth of both that has been ac?
cumulated since, whether his work on the Arno has ever 
been surpassed as a feat of advance.19 
Under those circumstances, and in the light of what 
follows, it would seem quite unusual if Castelli had 
not learned as much as he could about Leonardo and 
his work on this river. Abraham Wolf states that Cas?
telli was "deeply influenced by the Leonardo school, 
and [was] probably familiar with the Vatican com?
pilation of Leonardo's notes." 20 
Early in 1626 he sent to Galileo at Florence for his 
consideration, two treatises on that subject. During 
that year also, he was called to Rome by Pope Urban 
vin to serve as the papal consultant on hydraulics and 
as professor of mathematics at the University of 
Rome.21 Within two years thereafter, his famous book 
Delia Misura DelTAcque Correnti (perhaps die final 
version of the two treatises he had sent to Galileo) 
was published. 
The early chapters of Castelli's book were devoted, 
as previously mentioned, to a condemnation of die 
method of measuring streamflow as had been prac?
ticed by Frontinus during the early years of the Ro?
man Republic, and later by Fontana in his measure?
ment of the 1598 flood on the Tiber River. Most of 
the remaining chapters contained his explanation of 
the nature of velocity and its relation to the discharge 
of rivers. A few (slightly modernized) extracts of Sal-
usbury's translation of Castelli's work are presented 
below.22 When reading them it should be kept in mind 
that in general, these were the first statements to have 
been published dealing with such subjects. Although 
some of the terminology is archaic, the basic concepts 
are still sound. 
DEFINITION OF STREAMFLOW MEASUREMENT.?To meas?
ure a river or running water is, in our sense, to find out 
how many determinate measures, or weights of water in a 
given time passeth through the river or channel of water 
that is to be measured." 
8 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 
FLOATS FOR DETERMINING VELOCITY.? [The velocity of 
the water may be determined by] keeping account of what 
space a piece of wood or other body that swimmeth, is car?
ried by the stream in one determinate time, as for instance, 
50 pulses . . . 2* 
PENDULUM FOR TIMING OBSERVATIONS.?Because it will 
often be requisite to measure time exactly in the following 
problems, we take that to be an excellent way to measure 
time, which was shewed me many years since by Signore 
Galileo Galilei, which is as followeth: A string is to be taken 
three Roman feet long, to the end of which a bullet of lead 
is to be hanged of about two or three ounces; and holding 
it by the other end, the plummet is to be moved from its 
perpendicularity a palm more or less, and then let go, which 
will make many swings to and again, passing and repassing 
the perpendicular before it stay in the same. Now it being 
required to measure the time that is spent in any whatso?
ever operation, those vibrations are to be numbered that are 
made while the work lasteth; and they shall be so many 
second minutes of an hour if the string be three Roman feet 
long. But in shorter strings, the vibrations are more frequent, 
and in longer, less frequent; and all this followeth whether 
the plummet be a little or much removed from its perpen?
dicularity, or whether the weight of the lead be greater or 
lesser.25 
CONTINUITY OF FLOW IN STREAMS.??. . . those streams 
which carry equal quantities of water in equal times make 
not the same depths or measures (widths) in the river in 
which they flow unless when flowing in the river they acquire 
?or to say better?keep the same velocity. . . . 
Because of Castelli's strong disapproval of Fonta?
na's methods, it seems rather peculiar that in 1640, 
he arranged to have Fontana's report of that 1598 
flood republished. The fact that he had done so is 
shown in Figure 5 which represents the cover page 
thereof, and the cover page of one of the more re?
cent editions of Castelli's Delia Misura Dell'Acqua 
Correnti. The dates at which both of these reports 
originally appeared?1599 and 1628 respectively? 
mark the time at which the old Q = A concept was 
contested, and the time at which the modern Q = AV 
concept began taking its place. 
Free Floats 
With a change of focus from other-worldly concerns 
to those of the nature of the real world, the Renais?
sance in Europe stimulated the efforts of many re?
markable men, most notable among them being Leon?
ardo da Vinci (1452-1519). 
Among the more than 8000 note sheets still extant 
on which Leonardo da Vinci had written and drawn 
sketches, by far the greatest number of entries on any 
major subject therein was concerned with hydraulics. 
The one group of entries, which is of greatest concern 
at present, is that which dealt with the velocity distri?
bution of the water in rivers. Philosophers of the Mid?
dle Ages had contended mistakenly that the water in 
rivers flowed much faster near the bottom than at the 
top. In support of that contention, they would point 
to the well-known circumstance that if several holes 
were drilled in a large wooden tank filled with water, 
the velocity with which the water emerged from the 
lower hole was always greater than that from any of 
the other holes. To them, the conditions which pre?
vailed in large water tanks were identical to those in 
large rivers, and they would condone no experimen?
tation that would either confirm or deny any of 
their conclusions. 
Leonardo, who was intensely curious about all as?
pects of nature, was also a firm believer in experimen?
tation as the premise upon which to base belief. 
According to one eminent authority, Dr. Carlo Zam-
mattio, that intense curiosity "set him completely 
apart from those who preceeded him. His advent 
brought to the world a new age which aspired above 
all to UNDERSTAND." His notebooks reveal the manner 
in which his experiments were made on the velocity-
distribution in rivers. The sketch and notes about the 
rod floats he had made for that purpose appear in Fig?
ure 6 along with a recently-built replica of one of 
them.72 Figure 7 contains the author's concept, based 
on a group of such notes, showing Leonardo behind 
his odometer keeping abreast the float near the middle 
of the river. The project involved the following opera?
tions : 
1. His helper would release a float of just the 
proper length (short enough so as not to drag against 
the bottom) several yards upstream from the line 
stretched across the river. 
2. Leonardo would wait at that line with his odom?
eter set at "0 ." When the float arrived, he would start 
pushing the odometer down the path, keeping abreast 
the float, and singing the musical scale up and down 
say ten times. (According to Marinoni, he had trained 
himself to sing the scales at a precise rate, and knew 
the number of seconds it would take him to sing any 
number of them. He preferred that method to count?
ing his pulse because it was more convenient and un?
der most circumstances, more accurate.) 28 
3. Upon completing that "song," Leonardo would 
stop abruptly, note the distance recorded on the odo?
meter and, from the number of times he had repeated 
those musical scales, the time required for the float 
NUMBER 28 
MESVRE RACCOLTE 
DA GIOVAN 
F O N T A N A 
ARCHITETTO, 
DeWosiccrcfcitnento chehatmof&t. 
to it Fiumi, Torrenti, e fop che 
hanno caufato C inondatwnc a 
T^oma d "NataU, 1 5 9 8 . 
Riftampataadinftanza delSig. 
Domenico CafteJIi. 
I N R O M A 
Apprcflb An tonio M a r i a n , Gioiofi ? 
M . D C . XXXX. 
DELLA MISVRA 
DELL A C Q V E 
C O R. R E N T I 
D l D. B E N E D E T T O C A S T E L L I 
I t 
Ab\>at c di S. 3medettoMoyfw,e Matcnuttico 
DI PAPA VRBANO VIII-
Profefsore ncllo Studio di Roma. 
In auejla term edizjone accrefctuta del Second* libro, t di 
moke curiofe Scritture mm ptu flamfAte. 
ALL' I L L " ? E REV.M O S I G N O R 
ABBATE VRBANO 
S A C C H E T T L 
la BOLOGNA, per g t i H H . i t l D a m . M. DC.LJt. 
FIGURE 5. Title pages of Fontana's and Castelli's books. These books symbolize the passage 
of the old Q = A concept and the advent of the modern Q = AV concept for measuring water 
flow in conduits and in open channels. 
to have traveled that far. From this he would com?
pute the float's velocity. While all this was taking 
place, he would have observed whether the float tilted 
forward or backward, thereby noting whether the 
velocity near the top of the stream was greater or less 
than near the bottom. 
4. He would finally retrieve the float and return 
again to the point of beginning. His assistant would 
thereupon release another float at a greater distance 
from his side of the river. The whole procedure would 
then be repeated until the entire width of the stream 
had been covered and the velocity distribution 
throughout its entire cross-section had been deter?
mined. 
The conclusion Leonardo arrived at after having 
completed his experiments is noted in several places 
in his notebooks, but perhaps most completely in 
Codice Atlantico, folio 124 r. a, which has been trans?
lated as follows by MacCurdy: 
Of water of uniform weight, depth, breadth and declivity, 
that portion is swifter which is nearest the surface; and this 
occurs because the water that is uppermost is contiguous to 
the air, which offers but little resistance through its being 
lighter than the water; and the water that is below is con?
tiguous to the earth, which offers great resistance through 
being immovable and heavier than water. It follows that the 
part which is more distant from this base has less resistance 
than that above which is contiguous to the air, for this is 
light and mobile.28 
Leonardo's rod float is the earliest device to have 
been found so far that was specifically designed for 
the purpose of measuring stream velocities. The addi?
tional feature it provided, namely that of indicating 
a 
?1V?M| 
BLADDER 
"Let the rod project one braccio a t 
A N so that the displacement of the 
brick can be dist inguished at A N." 
ROD 
"This demonstrates whether the water 
is f lowing faster below or at the 
surface." 
fc^b**' 
FIGURE 6.?Leonardo da Vinci's rod float for investigating the subsurface water velocities in 
streams, as reconstructed by the author (a), from Leonardo's notes, (b) .(From da Vinci, Manu?
script "A," folio 42 v.) 
NUMBER 28 11 
FIGURE 7.?Leonardo conducting experiments on the velocity-distribution in streams. 
(Drawn by A. H. Frazier.) 
whether the surface or bottom velocities were greater, 
reflects some of the special genius with which Leon?
ardo was endowed. 
It may be interesting to note here that when 
Leonardo conducted these experiments, he obtained 
enough data (a detailed cross-section of the stream 
and velocity observations at numerous locations there?
in) to compute the stream's actual discharge. No 
evidence has been found, however, that he had pur?
sued any such objective, although on more than one 
occasion he had studied the rate of flow through or?
ifices. Apparently his only plan on this occasion was to 
make a velocity-distribution study. Aside from want?
ing to satisfy himself as to what the true circumstances 
were, he might also have wanted to demonstrate that 
the theories of contemporary philosophers (for whom 
he had very little admiration) were wrong. 
Although Leonardo's paintings and writings about 
art had received wide acclaim both during and after 
his lifetime, his 8000 or more pages of scientific notes 
failed to attract any immediate or widespread atten?
tion. At several places in those notes, he had expressed 
an intention to reorganize for publication those partic?
ularly relating to hydraulics. He had prepared several 
lists of chapter headings, and in several other instances 
he had drafted one or more paragraphs which were ob?
viously intended for use in such a publication. He 
never made, however, any further progress thereon 
before his death. Moreover, the persons who subse?
quently got possession of those notes only seemed 
interested in those which related to painting. 
Finally, an eminent hydraulic experimenter named 
Giovanni Battista Venturi (see pages 37-40) pub?
lished, in 1797, a booklet entitled Essai sur les ouvrages 
physico-mathcmatiques de Leonard de Vinci, which, 
at long last, focused attention on Leonardo's remark?
able scientific achievements. Suddenly the dozen or 
so persons and libraries that had acquired any pages 
from Leonardo's notebooks found themselves in pos?
sesion of unexpected and priceless treasures. 
12 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 
^ J J L L - ^ . , . ^ ^ . , . 35RS97?m 
a 6 c 
FIGURE 8.?Earliest floats post-dating Castelli's book on water velocities: a, Cabeo's rods, ca. 
1646; b, Barattieri's rod float, ca. 1663; c, Mariotte's double float, ca. 1680. (Drawn by A. H. 
Frazier, from Masetti, "Descrizione.") 
FIGURE 9.?Brunacci's combination single and double float, 
ca. 1805. (Drawn by A. H. Frazier, after Masetti, "Des?
crizione.") 
I 
Side vitw of Surface Float 
u-
Top view of Surface Float 
iLi-?L . 
IL 
TprW' Section of Sub-Surface Float 
Top view of Sub-Surface Float 
FIGURE 10.?A double float, such as was designed and used 
by General Ellis on the Connecticut River, ca. 1875. 
NUMBER 28 13 
There can be little doubt that men had long been 
aware of the existence of velocities in rivers by merely 
having observed materials floating on them. Accord?
ingly, floats became the first and most natural facility 
for studying velocities. It has already been shown that 
Leonardo used floats for that purpose, although his 
unpublished observations thereon failed to either come 
to the attention of, or to motivate, any immediate 
followers. In fact, more than 100 years elapsed before 
Benedetto Castelli's work aroused any general interest 
in the subject. Many scholars, including Abraham 
Wolf, have noted many similarities between Cas?
telli's comments about water velocities and those of 
Leonardo da Vinci's, and have expressed their beliefs 
that Castelli had made use of many of Leonardo's 
observations thereon when writing his book. Never?
theless, Leonardo had attracted relatively few (if any) 
immediate followers in this field, whereas Castelli had 
attracted a large number of them. It was Castelli's 
proposal to use floats for measuring velocities, not 
Leonardo's, that started the vogue in that respect, 
a vogue which has never completely disappeared. 
Among Castelli's numerous followers were several 
who preferred to use rod floats which, like Leonardo's, 
would travel in an upright position; others preferred 
wooden spheres, or balls of wax. It would be almost 
an endless task to describe them all, but a fair idea of 
how some of them appeared can be obtained from 
Figure 8 which shows three models used before the 
end of the 17th century by Nicola Cabeo (1585-
1650), G. B. Barattieri (1601-1677), and Edmc Mari-
otte (1620-1684), respectively. An additional feature 
(Figure 9) introduced by Vincenzo Brunacci (1768-
1818) in about 1805, consisted of merely providing a 
separate and completely loose ball along with Mariot-
te's double float. This additional ball was allowed to 
travel with the double float during each of its "runs." 
Its speed was generally greater than that of the double 
float because it was not held back by the more sluggish 
lower ball. Here, according to Masetti, is what Brun?
acci achieved with such equipment: 
Having determined with an ordinary float the speed at the 
surface, and having simultaneously measured the velocity at 
which the two-ball assembly travelled, he could quickly find 
FIGURE 11.?One of James Francis' rod floats. From the 
large set of rod floats used by James Francis while Chief En?
gineer of the Proprietors of Locks and Canals, Lowell, Mass?
achusetts, ca. 1855. It is held by one of his successors, George 
Whitaker (1907-1962). 
14 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 
the speed of the current at the depth to which the heavier 
ball had been lowered by using a very simple formula based 
on the theory of such a meter.30 
It should not be assumed from the foregoing re?
marks that free floats became increasingly scarce 
during the later centuries. Like practically all early 
velocity-measuring devices, they continued to make 
sporadic appearances even up to the present. With 
the publication of Humphreys' and Abbot's famous 
report on the Mississippi River, for example, double 
floats similar to that designed by Mariotte received 
official endorsement: 
Various methods were resorted to. Saxton's current 
meter was tried, but proved to be unsuited to measurements 
in a river of such great depth and violence of current. Only 
double floats were found to give reliable results. [Italics 
added.] 31 
Perhaps the most carefully designed double floats 
(Figure 10) ever to have received actual field use 
were those that General Theodore G. Ellis (1829-
1883) made for his studies on the Connecticut River 
between 1867 and 1877 under General Humphreys. 
Perhaps the best rod floats (Figure 11) ever to have 
been designed, were those of the set used by the dis?
tinguished hydraulic engineer, James Francis (1815-
1892) of Lowell, Massachusetts, who (among other 
purposes) used them to develop the famous Francis 
Weir formulas. 
FIGURE 12.?Camillo Agrippa, his ship, and ship's log, ca. 1595. 
(From Agrippa, Nuove Inventione.) 
NUMBER 28 15 
Tethered Floats 
The advent of "free" floats was followed by one 
that will be called here "tethered" floats, because 
the major feature thereof consisted of a ball, generally 
heavier than water, to which a cord was attached to 
limit the distance that it could travel downstream. 
The use of such devices had been anticipated in the 
navigation field by an early ship's log, a description of 
which appeared in a booklet entitled Nuove Inven-
tione di Camillo Agrippa, published in 1595.32 A por?
trait of Agrippa, his ship, and a close-up view of his 
invention appear in Figure 12. As may be seen in the 
close-up view, the device consisted of a large frame 
shaped like a carpenter's square which would be sus?
pended either from the ship's foremast, or from a 
boom extending outward from the ship's rail. Its 
downstream leg, which was graduated throughout its 
length, would be brought to rest horizontally, just 
above the water's surface. The ball, heavier than 
water, was suspended from a cord fastened to the 
upper edge of the frame, the cord being sufficiently 
long to permit the ball to be submerged a foot or two 
below the surface of the water. As the ship moved 
forward, the ball would lag behind the other parts of 
the frame by an amount that depended upon the 
speed of the ship. The extent of that lag could be 
observed from the position of the cord as it crossed 
in front of the scale on the horizontal leg. By position?
ing those graduations appropriately, the actual speed 
of the ship could he read thereon. 
Whether Domenico Guglielmini (1655-1710) had 
ever heard of Agrippa's ship's log is not known, but 
in his book, Aquarium Fluentium Nova Methodo In-
quisitia, published in 1690 and 1691, he described a 
velocity-measuring facility called a "quadrant and 
ball," which operated on exactly the same principle. 
Figure 13 shows two positions of the ball (as would 
be caused by two different velocities), and force di?
agrams that he used for determining the proportions 
the two velocities bore to each other. 
Guglielmini (Figure 14) became the most highly 
FIGURE 13.?Guglielmlni's "quadrant and ball," Ca. 1690. 
The force diagrams indicate the proportions one velocity 
bears to another. (From Guglielmini, Opera Omnia.) 
FIGURE 14.?Domenico Guglielmini. 
(Courtesy of Hunter Rouse.) 
16 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 
respected hydraulic engineer in Italy during his time. 
He was born in Bologna 27 September 1655 and re?
ceived an exceptionally good education. A degree of 
Doctor of Physics was conferred on him by the Uni?
versity of Bologna in 1678. His greatest interests first 
centered around astronomy, but they soon shifted to 
hydraulics. The Senate of Bologna then appointed 
him to the positions of First Professor of Mathematics 
and General Superintendent of Waters. While holding 
those positions, he wrote several treatises about flow?
ing water, the first of which has been cited above. In 
1694 the City of Bologna founded a new chair of 
Professor of Hydrometry in its university and gave it 
to him. The word "hydrometry" made its first appear?
ance in that title. After having published a book on 
The Nature of Rivers in 1697, he was chosen a mem?
ber of the Italian Royal Academy of Sciences. One 
of his early biographers reported, "This book?an 
Original of its kind, made a great Noise . . The 
Common-wealth of Venice, envying the Happiness of 
Bologna, called him in the Year 1698 to the Professor?
ship of the Mathematicks at Padoua.'' 33 In 1702 he 
became that university's Professor of Theoretical 
Physics. Soon thereafter, chemistry became his favor?
ite subject, so before long he wrote a few books on 
chemistry. The last thereof was published during the 
final year of his life, 1710. 
Because of the great advances in hydraulics since 
the 17th Century, most modern hydrographers are not 
likely to display as much enthusiasm for Guglielmini's 
work as did his contemporaries. While most of it was 
quite sound, his quadrant and ball produced very 
misleading results particularly when used on deep 
swift rivers. Its fault rested in the fact that it failed 
to eliminate the effect of the pressure which the flow?
ing water exerted against the cord from which the 
lower ball was suspended. As that ball came closer to 
the bottom of the stream (where lower velocities nor?
mally occur, and where the angle as read on the quad?
rant should become smaller), the drag of the water 
against the greater length of cord which was paid out 
would more than offset the decrease of pressure 
against the ball, and the angle read on the quadrant 
would become larger. Obviously unaware of that in?
herent fault in his instrument, Guglielmini stated un?
equivocally at several places in his earlier works that 
the velocity at the bottom was greater than near the 
top. He is said to have changed that belief in later 
years, but so far, no evidence has ben found to indi?
cate that he attributed any of that error to his in?
strument. Just how much that effect could distort 
the true results will become evident by comparing the 
Feet per Second 
0 5 10 15 20 2. 
Feet per Second 
20 
40 
60 
80 
at 
x> 
100 Bottom 100 
0 
20 
40 
60 
80 
Max. 
FIGURE 15.?Comparison of Guglielmini's erroneous vertical velocity curve with its modern 
counterpart: a, Guglielmini's curve developed with his quadrant and ball; b, modern curve 
developed with modern equipment. 
NUMBER 28 17 
vertical velocity curves shown in Figure 15. At the 
right thereof is what modern hydrographers have 
found to be the correct general shape of such curves, 
whereas to the left of it is the same type of curve 
based on data which Guglielmini himself observed 
with his quadrant and ball on a 35-foot-deep river.34 
I t will be seen that one is practically the reverse of the 
other insofar as the vertical velocity distribution is 
concerned. 
Despite its faults, Guglielmini's quadrant and ball 
attracted many followers. Figures I6a-d show two of 
the various types which were obviously inspired by his 
model. Figures 16a, b resemble his original model 
closely; those in 16c, d reflect a preference for a 
weighted rod rather than for a weighted ball; Figures 
16tf, / differ from the others in that the quadrant has 
been replaced by spring scales; and those in I6g, h 
illustrate an innovation which, although much more 
cumbersome for use in deep swift water, would tend 
to eliminate much of the fault found with Gugliel?
mini's original model. 
^*?^3i^3^^^^5?i^5J^^iiiti^gSiw^*^ 
^3*guri!a^ia^ti!^>*=awi=^i!SisSj^?i!=5Si' 
FIGURE 16.?Successors to Guglielmini's quadrant and ball: 
a, Cava's square, ca. 1721; b, Ximenes' quadrant, ca. 1752; 
c, Ferrari's sectional rod, ca. 1796; d, Venturoli's com?
pound pendulum, ca. 1796; e Ximenes' clock-spring device, 
ca. 1752; /, Ximenes' spring-scale device, ca. 1752; g, Lorg-
na's device, ca. 1777; h, Barbantini's hydraulic counter?
weight, ca. 1814. (Redrawn by A. H Frazier after Masetti, 
"Descrizione") 
18 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 
PADDLES 
Man's early use of crude paddles to help propel a 
log or raft across a stream obviously extends back into 
prehistoric times, and the principles learned on those 
occasions ultimately became applied to a considerable 
group of current meters. The forces that are in 
effect when paddles are placed in water do not always 
produce the same results. If a person sitting in a canoe 
applies a backward force to the paddle, for example, 
the canoe will move forward, whereas if the person 
were sitting on the bank of the stream and held the 
paddle in the current, the paddle would tend to be 
pushed backward. It is this latter effect that was 
ultimately adopted in the design of current meters for 
measuring the velocity of running water. 
The amount of force required to hold the paddle 
squarely against the current would depend upon the 
a 
en 
jy# 
o 
FIGURE 17.?Santorio's inventions: a, water current meter; 
b, anemometer. (From Santorio, Commentaria.) 
FIGURE 18.?Gauthey's current meters, ca. 1779. (a, from 
Van Winkel, "Streamflow"; b, drawn and reconstructed by 
A. H. Frazier after Masetti, "Descrizione.") 
dimensions of the paddle and the velocity of the cur?
rent. By using the same paddle throughout a series of 
experiments, and by using some method of measuring 
the force required to prevent the paddle from swinging 
downstream, the relative speed of the current at many 
different locations could be determined. The actual 
speeds of the water could also be determined thereby, 
but the mathematics involved would be considerably 
more complicated. 
The earliest record of a paddle-type current meter 
was that reported by Dr. Santorio Santorio (1561-
1636). Encyclopedias report that he was the world's 
first iatrophysicist (one who explains diseases of the 
body in terms of physics rather than of chemistry), 
and the inventor of many useful medical instruments. 
The particular instrument that brought Santorio the 
most acclaim was his invention of the clinical ther?
mometer. It was similar to Galileo's thermometer 
(which was designed to measure atmospheric temper?
atures), but Santorio modified it in such a way to 
measure body temperatures of his patients who were 
afflicted with a fever. In 1610, he turned his attention 
NUMBER 28 19 
^e?*?3???jsi?^?6feifjg??H?fe*' 
FIGURE 19.?Ximenes' paddle type current meters, ca. 1780. 
(Drawn by A. H. Frazier after Masetti, "Descrizione.") 
J&SJT/. 
~^se*r?\/('?^" y?*/*r's/f/f//-< ? 'J/rffc"""c/stf 
&&TJJ 
FIGURE 20.?Christiaan Bruning 
and his current meter, ca. 1788. 
20 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 
to the construction of an anemometer and a water 
current meter (Figure 17). As Carlo Zammattio has 
pointed out, Santorio had made his drawings known 
to the public before 1611, almost 18 years before the 
first edition of Castelli's famous work on water vel?
ocity was published. The circumstances under which 
they were invented, as translated by Zammattio from 
Santorio's book Commentaria In Primam Fen Primi 
Libri Canonis Auicennae, are presented below: 
Some people are benefited, and others harmed during 
rainy weather. Similarly, the heavy impact of falling or 
running waters tends to produce sleep in some, and to pre?
vent sleep in others. But I would like to mention here a 
condition I had observed in Croatia, where there is a place 
renowned for the noise of winds, and for the great tumult 
of rushing waters. At some times people of the community 
are aroused from sleep by this uproar, and at others they 
are lulled to sleep by that same noise. I therefore proposed, 
as a means of subtly ascertaining the reason for those cir?
cumstances, that one should weigh, with a balance scale, the 
amount of impact produced under both circumstances. When 
urged by friends to show how that could be done, I prepared 
two staters (Roman balances) on both of which a plate is 
mounted at right angles. By means of the first (with the 
plate pointing upwards), the impact of the winds could be 
weighed; by means of the second (with the plate pointing 
downwards), the impact of the water. The one having the 
plate pointing upward for measuring the impetus of the wind 
helped us to predict when such winds tended to increase. 
We could thus forecast weather at sea, and could avoid the 
peril of sinking ships. It further provided the means whereby 
we could be more sure as to whether the impact of the winds 
tended to increase or decrease. Other uses for this device are 
described in the book regarding medical instruments. 
The other instrument (on which the plate hangs down?
wards) allows us to weigh the amount of impact produced 
by running waters. It might have primary usefulness for im?
proving the efficiency of mills and for other applications. In 
consequence of its use, we shall be able to ascertain what 
amount of impact has beneficial properties, and what 
amounts would have harmful properties for our patients. 
Actually, if certain amounts of impetus or noise are salubri?
ous, and others are unsalubrious, by what better means 
could we measure the effectiveness of our medicines? M 
Zammattio has suggested that the location in Cro?
atia (now part of Yugoslavia) to which Dr. Santorio 
had referred, may have been at the great Caverns of 
St. Canziano del Carso, some 60 miles east of Trieste, 
Italy. There a river disappears with a tumultuous roar 
into a vast underground cavern. There also, occurs 
the "bors"?a terrific wind that blows down from the 
European plains throughout the year. 
Although Santorio's device measured only the im?
pact of the water striking the plate (making no 
attempt to convert the results into actual velocity 
FIGURE. 21?Karl F. Keeler (b. 1888) 
and his deflection meter. 
NUMBER 28 21 
values), it should be realized mat the mathematical 
tools for making such conversions had not yet been 
conceived. 
Beginning in 1779 (more than one and one-half 
centuries after the advent of Dr. Santorio's devices), 
a whole rash of paddle-type current meters appeared. 
As a matter of fact, they have continued to do so up 
to the present. The earliest on record of this new crop 
are the two made during 1779 by the great French 
canal builder, Emiland Marie Gauthey (1732-1806). 
Gauthey was a graduate and later an Inspector 
Generale of the Ecole des Ponts et Chausees of Paris, 
the foremost engineering college in the world at that 
time. Gauthey's model (Figure 18a) bears such a 
close resemblance to the one designed by Santorio, 
that it is tempting to assume that he might have heard 
about the doctor's model. It may be noted that while 
the principle of operation is the same in both models, 
that shown in Figure 18a measures the water's impact 
against the plate (while it is kept normal to the cur?
rent) by means of a balance, whereas the other (Fig?
ure 186) measures it by means of a spring scale. 
During the next year Leonardo Ximenes (1716-
1786) introduced the three models shown in Figure 
19. Figure 19a was intended for measuring surface 
velocities only, but Figures 196 and c could be used 
to any depth not exceeding the overall height of the 
framework. 
In all three of Ximenes' models, the panels (or 
blades) were allowed to swing downstream?the de?
gree depending upon the speed of the current?in 
contrast to the earlier equipment in which the blade 
had to be held normal to the current at the time 
readings were taken. In the first model (Figure 19a) 
the pressure against the plate is resisted entirely by 
the weight of the panel itself. In Figure 196 a single 
weight provides the force which resists the pressure 
against the blade (which in this case is suspended to 
swing laterally rather than vertically). In Figure 19c 
the weight of the blade, plus that of an additional 
weight, combine to oppose such pressures. 
Since the manufacture of "paddle-type" current 
meters continues to the present, and therefore, are 
too numerous to cover here, only two additional mod?
els will receive attention. That shown in Figure 20 
was designed by Christiaan Bruning (1736-1805), a 
Dutch hydraulic engineer, who had been educated at 
Heidelberg University and who ultimately, in 1803, 
became the Director General of Holland's river and 
sea operations. It may be noted that in his device, die 
impact of the water tended to push the flat plate 
straight backwards, but was restrained from doing so 
through a counter pressure applied at the balance 
scale at the upper end of the support rod. Readings 
obtained from the amount of weight required to es?
tablish an equilibrium could be converted into figures 
representing the velocity of the water. Bruning's 
paper 36 about this equipment was published in Hol?
land in the late 1780s, for which the Dutch Academy 
of Sciences awarded him a gold medal. 
Reinhard Woltman, whose current meter will be 
discussed later in this study, was a great admirer of 
Bruning, and in 1790, when Woltman published an 
account of his own current meter,37 he included 
therein the drawings of the Bruning meter shown in 
Figure 20. 
The deflection meter shown in Figure 21 was de?
signed by Karl Fairbanks Keeler, an American hy?
draulic engineer. This meter, constructed in 1937 by 
Leupold, Volpel & Co. of Portland (now Leupold and 
Stevens, Incorporated of Beaverton, Oregon), is per?
haps the most sophisticated paddle-type device ever 
built in that it has been interconnected with a water-
stage recorder, which registers simultaneously both 
the height of the stream and the angle assumed by 
the blade. Its purpose is to help obtain records of the 
flow in canals that are subject to backwater variations. 
A number of these models have been manufactured 
by the Leupold and Stevens firm. Most of them have 
been installed at gaging stations operated by the In?
ternational Boundary and Water Commission, United 
States and Mexico, in which Keeler had been em?
ployed for many years as the Supervising Hydraulic 
Engineer. 
PADDLE WHEELS 
Paddle wheels similar to those that propelled the 
early Mississippi River steamboats?but much smaller, 
of course?have been used fairly extensively both for 
registering the speed of a ship at sea and the surface 
velocities of the water flowing in rivers. Here again, 
the application in the navigation field was the earlier 
22 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 
of the two. The first published record of a paddle 
wheel for use as a ship's log was contained in the first 
volume of Vitruvius' book on Architecture, written 
in about the first century B.C.38 A drawing, based on 
Vitruvius' description of that device is shown in Fig?
ure 22. As may be seen, a pair of paddle wheels, one 
on each side of the ship, but mounted on the same 
shaft, drove a train of reduction gears. The final gear 
in the train just cleared a special upper deck in the 
hold of the ship. It had a series of holes through it 
which formed a circle just within its outer circum?
ference. At regular intervals of time a single round 
stone would be placed in each of those holes, and 
these stones would be pushed along by the gear during 
the course of its circular travel. The reduction accom?
plished by these gears was so great that the ship had 
to travel a distance of one mile to cause each succes?
sive hole to reach a point where an opening had been 
cut through that special deck to allow each stone in 
its turn to drop through into a large bronze container 
on the lower deck. Each mile of travel would therefore 
be announced by a loud "clang" as the stone would 
strike against the rim of that container. By counting 
the number of stones that had accumulated therein, 
the Captain could determine the number of miles 
which the ship had traveled. 
This device also could be used to measure velocities 
in rivers by merely anchoring the ship in the current 
and allowing the log to perform its function in the 
same manner as it does when the ship is moving in 
still water. 
European Contributions 
The earliest paddle wheel to have been found so 
far which was built specifically for measuring the vel?
ocity of water flowing in open channels, is that made 
by Luigi Ferdinando Marsili (1658-1730), sometimes 
spelled Marsigli (Figure 23). He used it in about 1681 
for studying the velocities in the Bosporus between 
^^z^g^^z^az^^zz^zn^g^z^^^arT^^z^^as^gs^gz 
V/////////////77777, ^////////////////////A 
? ^ Af +fa/t>z 
FIGURE 22.?World's first mechanical ship's log as described by Vitruvius in first century B.C. 
(Drawn by A. H. Frazier.) 
*->>* Cross-Section A-A 
FIGURE 23.?Marsili iMarsigliJ and drawings of his current meter. (Portrait from Enciclope-
dia Italiana di Scienze; drawings from Milanese, "Santorio.") 
24 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 
the Black Sea and the Sea of Marmora, and later on 
rivers in the Danube Valley. A translation of his 
description of that meter, containing a few minor 
modifications from that which was recently prepared 
by Fernando Milanese, an engineer of Milan, Italy, 
follows: 
To measure the velocity of the current at the Leandro 
Tower, I built a wooden apparatus which had a wheel pro?
vided with six blades, each about a foot broad. I fastened 
the wheel to a tapered shaft about 5 feet long, and installed 
a pointer at one end to assist in counting the number of 
revolutions performed by the wheel as the water struck 
directly against the lowermost blades. . While holding 
the axle of the wheel in a horizontal position with just the 
lower blades submerged in the water, a six-inch-long pen?
dulum made 100 oscillations while the wheel, as observed 
from the pointer, made 38 revolutions. By performing sim?
ilar experiments, the velocities of any river can be compared 
to the one that I had measured.39 
Many writers, obviously unaware of Marsili's earlier 
work, have credited Francesco Domenico Michelotti 
(1710-1777), Professor of Mechanics at the Univer?
sity of Torino (Turin) with having been the inventor 
of the paddle-wheel-type current meter (Figure 246). 
His two-volume work on hydraulics entitled Speri-
menti Idraulici 40 contains among its illustrations, the 
two shown in Figure 24. Probably the leading hy?
draulic engineer in Italy, Michelotti had the oppor?
tunity to use most of the velocity-measuring devices 
which were in vogue during his time. Figure 24a ap?
peared at the beginning of one of his chapters. It 
shows most of the equipment that a professional 
hydrographer of the 1760s might have taken on an 
extended field trip. The following items therein can be 
identified: (1) a Pitot tube (invented in 1730); (2) 
a level and leveling rod; (3) a quadrant and ball 
(such as invented by Guglielmini) ; and (4) a wicker 
stool for the comfort of the note-taker of the party! 
One item with which Michelotti also experimented, 
but which does not appear in either of these illustra?
tions, was a paddle-type meter similar to the one pre?
viously shown in Figure 18a. 
During the 1700s, leadership in the field of hydraul?
ics slowly shifted from Italy to France. No doubt the 
ample funds that the French government supplied for 
research on this subject did much toward creating the 
change. Then too, during that century, mathematics 
had reached a stage where astute researchers could 
apply it to their hydraulic investigations. 
Prominent among those who made use of both 
laboratory and mathematical facilities was Pierre Louis 
Georges Dubuat (1734-1809), a lieutenant in the 
Royal Corps of Engineers. The eminent engineer, 
writer, and educator, Hunter Rouse has provided the 
following translation from one of Dubuat's works re?
vealing the state of the science as of the 1780s: 
All that concerns the uniform course of the waters of the 
face of the earth is unknown to us; and to obtain an idea 
of how little we do know, it will suffice to glance over what 
we do not: To estimate the velocity of a river of which one 
knows the width, the depth, and the slope; to determine to 
what height it will rise if it receives another river in its bed; 
to predict how much it will fall if one diverts water from it; 
to establish the proper slope of an aqueduct to maintain a 
given velocity, or the proper capacity of the bed to deliver 
to a city at a given slope the quantity of water which will 
satisfy its needs; to lay out the contours of a river in such 
a manner that it will not work to change the bed in which 
one has confined it; to calculate the yield of a pipe of 
which the length, the diameter, and the head are given; to 
determine how much a bridge, a dam, or a gate will raise 
the level of a river; to indicate to what distance backwater 
will be appreciable, and to foretell whether the country will 
be subject to inundation; to calculate the length and the 
dimensions of a canal intended to drain marshes long lost 
to agriculture; to assign the most effective form to the en?
trances of canals, and to the confluences or mouths of rivers; 
to determine the most advantageous shape to give to boats 
or ships to cut the water with the least effort; to calculate 
in particular the force necessary to move a body which floats 
on the water. All these questions, and infinitely many others 
of the same sort are still unsolvable: Who would believe i t ?" 
Later, among those same works Dubuat expressed 
the fundamental principle which has thrown wide the 
doors for analyzing mathematically the flow of water 
in conduits and open channels. David Brewster, who 
had himself designed a current meter as will be dis?
cussed later, described the circumstances which led to 
that discovery as follows: 
In studying the motion of canals and rivers, it occurred to 
him [Dubuat] that if water possessed perfect fluidity and 
flowed in a channel infinitely smooth, its motion would be 
constantly accelerated like that of heavy bodies descending 
upon an inclined plane. But as the velocity of a river is not 
accelerated ad infinitum, but soon arrives at a state of uni?
formity, and is not afterwards increased without some cause, 
it follows that there is some obstacle which destroys its ac?
celerating force, and prevents it from impressing upon the 
NUMBER 28 25 
water new degrees of velocity. This obstacle must therefore 
be the viscidity of the water, which gives rise to two kinds 
of resistance, one, namely, which proceeds from the intestine 
motion of an imperfect fluid, and the other from the natural 
adhesion of its parts to the channel in which it flows. Our 
author, therefore, found it to be a general principle, "that 
when water runs uniformly in any channel, the accelerating 
force which obliges it to run is equal to the sum of all the 
resistances which it experiences, either from its own viscidity, 
or from the friction of its channel." 
The result of this investigation was published in 1779, in 
the first edition of his Principes d'Hydraulique . . . . 
Through the influence of M. de Fourcroy, director of the 
Royal Corps of Engineers, the French Minister ordered an 
annual sum to be put at the command of the Chevalier Buat 
[Dubuat], for the purpose of performing a set of experiments 
upon this important subject; and during the years 1780, 
1781, 1782, and 1783, he was constantly occupied with these 
experiments. . . 
In 1783, when M. Buat's experiments were finished, they 
were submitted to the Academy of Sciences through the 
minister of war, and were afterwards published in 1786, 
Hli^J'-W^ g p g g j j B ^ g ^ ^ g g j s y B i B S g s w ' I .juuyx MUU 
Piqi I - L - H - I I , 
FIGURE 24.?Stream-gaging equipment: a, ca. 1767; b, Michelotti's devices, ca. 1767. 
(From Michelotti, Sperimenti Idraulici.) 
26 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 
under the title of Principes d'Hydraulique verifies par un 
grand nombre d'experiences faites par ordre du gouvern-
ment. A third volume of this work was published in 1816 
under the title of Principes d'Hydraulique et de Pyrodyna-
mique.42 
Probably the largest item of laboratory equipment 
which Dubuat had occasion to use during his experi?
ments consisted of a canal, 15 feet wide over which 
he arranged to have a bridge built which just cleared 
the surface of the water. In this canal he could "by 
means of a gate, produce a stream 3 feet deep, with 
a velocity of more than 40 inches per second." 43 For 
measuring subsurface velocities he first used a Pitot 
tube, but upon finding it was difficult to read because 
of the tendency of the water in the tubes to oscillate 
continually, he had a substitute made which consisted 
of "a simple tin tube large enough so that we may 
place in it a float which will indicate the elevation of 
the water with greater precision than when it is ob?
served through glass." 44 The lower (bent) extremity 
terminated in a plane surface pierced by a small hole 
at its center for diminishing the oscillations in the 
water column. The float supported a slender rod, 
which extended vertically therefrom for facilitating 
observations on an adjacent scale. 
His experience with this device led Dubuat to per?
form numerous experiments with devices such as 
shown with his portrait in Figure 25. (Note the tiny 
float with its vertical rod in the second drawing from 
the left. By opening just one of the holes therein for 
each observation, he evaluated the pressure distribu?
tion across the entire face of the plate.) 
Dubuat 's most important laboratory facility for 
measuring surface velocities consisted of a wooden 
paddle wheel (Figure 26) similar to that used by 
Michelotti, but much lighter. Its rotor weighed only 
1114 ounces, and the diameter as measured from the 
center of one plate to the center of the one opposite it, 
was 2 feet. A replica of this paddle wheel is in the 
Smithsonian collection. 
An obituary of David Brewster (1781-1868) that ap?
peared in the 11 April 1868 issue of Harper's Weekly 
described him as "one of the greatest philosophers of 
our age." In addition to his having received numer?
ous awards and academic honors, he held fellowships 
in the Royal Societies of Edinburgh and of London, 
and he was a foreign associate of the French Institute. 
In 1831 he became one of the founders of the British 
Association for the Advancement of Science. No doubt 
the major triumph among his many literary accom?
plishments was his 22-year editorship of the monu?
mental Edinburgh Encyclopaedia. Tha t encyclopedia 
has especial significance here because its Volume 10 
contains, under the heading "Hydrodynamics," the 
most comprehensive and learned historical review of 
? 
FIGURE 25.?Pierre Louis Georges Dubuat and 
some of his experimental models. (From Rouse and 
Ince, History of Hydraulics; courtesy of Hunter 
Rouse.) 
NUMBER 28 27 
that subject to have been written up to 1832, the time 
of its publication. 
Experimentally, his major achievements were most?
ly concerned with polarized light and the crystals 
with which it could be produced. While the scientific 
aspects of his work thereon deserve high acclaim, the 
many millions of nonscientific persons who have 
looked into a kaleidoscope (a still popular toy that 
resulted from his investigations) may enjoy knowing 
that Brewster had invented it in 1816. 
The third edition of James Ferguson's multivolume 
work, entitled Lectures on Select Subjects . . ., in?
cludes Brewster's notes on the most recent discoveries 
in the arts and sciences, 45 and contains the earliest 
description and illustration of Brewster's paddle wheel 
current meter (Figure 27). 
To determine the velocity of water with this meter, 
it would be held so that just the lowermost paddles 
are completely immersed in the water while they faced 
FIGURE 26.?Replica of Dubuat's "moulinet" for measuring 
the surface velocities of water in rivers and canals, ca. 1780. 
(NMHT 317672, photo by A. H. Frazier.) 
FIGURE 27.?Sir David and his paddle wheel type meter. 
(Portrait from Harper's Weekly, / / April 1868; drawing 
from Ferguson, Lectures on Select Subjects.) 
28 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 
directly into the current. The amount of time required 
for the wheel to make a certain number of revolutions 
would then be determined, and the velocity computed 
therefrom, basing such computations on the assump?
tion that the effective circumference of the wheel (that 
which passes through the center of each of the pad?
dles) will travel at the same speed as the water at that 
location. The number of revolutions could be checked 
by counting the number of threads which the wheel 
had advancd along the threaded axle. 
Although the information contained in Ferguson's 
Lectures does not make it clear as to whether Fer?
guson or Brewster had conceived of the idea regard?
ing this meter, a book published by Giovambisto 
Masetti about a year later, gives the credit to Brews?
ter.40 
American Innovations 
Beginning in 1830, certain paddle wheels took on 
much larger dimensions and a somewhat different 
function, that of determining the discharge of the 
stream directly. To be sure, the water's average vel?
ocity could be determined in the process (by dividing 
the discharge by the cross-sectional area at any loca?
tion in the stream), but that information ceased to be 
of interest when the total discharge became known. 
These mammoth wheels made their initial appear?
ances in Lowell, Massachusetts, then the fastest grow?
ing industrial town in America. There, at the conflu?
ence of the Concord and Merrimack rivers, an ideal 
situation existed for developing water power on an 
unprecedented scale. A company called the Propri?
etors of Locks and Canals on the Merrimack River 
had been formed which offered to sell in package lots, 
entire cotton mills, complete with machinery, dormi?
tories for the employees, and, for a continuing fee, all 
of the water required for its operation. The first mills 
sold under this plan were purchased by the Flamilton 
Company. The earliest thereof went into operation in 
1826; the second in 1827; and the last in 1830. Sam?
uel Batchelder who, up to 1824 had operated a small 
New Hampshire mill, was selected as the Company's 
Agent (Manager) , and I thamar A. Beard (1789-
1871) (Figure 28) formerly the preceptor of an aca?
demy at nearby Littleton, was selected for its pay?
master. The man who constructed the millwheels for 
these and all of the other early Lowell mills was John 
Dummer. 
FIGURE 28.?Ithamar A. Beard. (From Lowell Historical 
Society collection, Lowell, Massachusetts; photo by A. H. 
Frazier.) 
In 1830, Batchelder decided it was time to deter?
mine the overall mechanical efficiency of the Hamil?
ton Mills, and Beard, who had spent much time 
educating himself as a hydraulic and mechanical en?
gineer, was put in charge of that work. Efficiency 
studies require the highest order of accuracy in all of 
the measurements that enter into the problem, and 
this was especially true with respect to the streamflow 
measurements. None of the methods then in vogue 
seemed accurate enough for his purpose, so Beard, 
with the help of John Dummer, developed a special 
paddle wheel for making them so (Figure 29) . The 
sides and bottom of the selected measuring section on 
the Hamilton Canal were thereupon lined with heavy 
planking, with a section in the bottom planks carved 
out to match the curvature of the wheel. The wheel 
itself was nineteen feet three inches in diameter, and 
fifteen feet broad. Only the lower one-third of it was 
NUMBER 28 29 
submerged in the water after its installation, and less 
than one-fourth of an inch clearance occurred be?
tween the wheel and any of the planks in the lining. 
The wheel was shaped like the paddle wheels on Mis?
sissippi River boats except that the compartments be?
tween successive paddles were so completely enclosed 
that no water could escape from one compartment 
into the next. Essentially all of the water therefore 
became trapped in the completely filled compartments 
on the wheel as the oncoming water caused it to re?
volve. The volume of water so trapped during each 
revolution of the wheel was readily computed. By 
timing the number of revolutions of the wheel during 
a given "run," the discharge, in cubic feet per second 
could easily be determined.47 The accuracy of this 
method is second only to that conceived by Hero of 
Alexandria (Figure 3) . 
It is of interest to note that the Lowell Courier for 
3 October 1840 (and for several issues thereafter), 
carried an advertisement headed "I thamar A. Beard, 
Civil Engineer." Among the various items listed there?
in as services which he performed, were "measuring 
and computing the quantity of water supplied by 
streams." This is believed to be the earliest advertise?
ment offering such services ever to have been pub?
lished in the United States. 
In 1841, the Proprietors of Locks and Canals de?
cided that it would be to their best interests to know 
the amount of water flowing in the other canals in 
Lowell (Figure 30). They accordingly engaged three 
of the most outstanding American engineers of the 
time to determine by the highest authority, the quan?
tities of water-power drawn by the several mills. They 
were James Fowle Baldwin (1782-1862), George 
FIGURE 29.?Measuring the flow in the Hamilton Canal with Beard's paddle wheel in 1830. 
(Drawn by A. H. Frazier.) 
30 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 
jy 
P L A N OF 
C A N A L SYSTEM 
PROPRIE-TOR-S OF THE L O C K S AND C A N A L a 
MAY 2 9 1941 L O W E L L , M A S S 
Note:-
Num\> 
Shouj 
FIGURE 30.-?The canals of Lowell, Massachusetts. 
Washington Whistler (1800-1849), and Charles S. 
Storrow (1809-1904). No finer group of engineers 
had ever previously been brought together for such 
an undertaking. 
James Fowle Baldwin (Figure 31a) was the son 
of Loammi Baldwin, builder of the famous Middlesex 
Canal between Lowell and Boston. Dr. Parsons, in his 
biography of Baldwin, declared that he was surpassed 
by none as a scientific and practical engineer. 
George Washington Whistler (Figure 316), father 
of the artist, has been honored by his fellow engineers 
with a cenotaph at the Greenwood Cemetery in 
Brooklyn, New York, which carries the following in?
scription : 
This cenotaph is a memorial of the esteem of his friends and 
companions . . . . Educated at the U.S. Military Academy, 
he returned from the Army in 1835 and became associated 
with William Gibbs McNeill. They were in their time ac?
knowledged to be at the head of their profession in this 
country. . . . 
In 1842, Whistler was commissioned by Czar Nicholas 
of Russia to take charge of the construction of a 
railroad between St. Petersburg and Moscow. 
Charles S. Storrow (Figure 31c) was perhaps the 
most highly educated hydraulic engineer in the coun?
try at that time. After graduating (at the head of his 
class) from Harvard in 1829, he spent several months 
in Loammi Baldwin's extensive engineering library 
in Woburn, Massachusetts, studying the English, 
French, and Italian books on that subject. Then, 
sponsored by Baldwin and the Marquis de Lafayette, 
he gained admission to what was then the world's 
leading engineering college, the Ecole des Ponts et 
Chaussees in Paris. And after completing three years 
of study, he visited England to learn what he could 
about the new Stephenson steam locomotives which 
had recently been constructed there. 
He returned to Boston in April 1832. Construction 
work on the Boston and Lowell Railroad had just 
begun, and he obtained a position with his good 
NUMBER 28 31 
FIGURE 31.?Three eminent engineers who measured the discharge of Lowell canals in 1841: 
a, James Fowle Baldwin; b, George Washington Whistler; c, Charles Storrer Storrow. (a, Cour?
tesy of Steponas Kolupaila; b, from The Illustrated American, 25 May 1895; c, from Engineer?
ing News, 16 February 1893.) 
friend, James Fowle Baldwin, the Chief Engineer in 
charge of its construction. When the first trial run 
on this railroad was made between Lowell and Boston, 
Charles Storrow controlled the throttle of the Steph?
enson locomotive. From 1836 to 1845 he was the agent 
(general manager) of that railroad. During the 
earlier years of his work thereon, much of his spare 
time was devoted to writing his book, A Treatise on 
Water-Works. It was published in 1835 and con?
tained the most authoritative information then avail?
able on hydraulics from both European and American 
sources. It is believed to be the first book completely 
devoted to hydraulics ever to have been written by an 
American and published in America. 
Another participant in that canal-measuring project 
was James Francis (1815-1892). He had come to 
Lowell with George Washington Whistler in the early 
1830s at the time Whistler became engaged as En?
gineer of the Proprietors of Locks and Canals for the 
special purpose of building, in the Lowell Shops, rail?
road locomotives similar to those built by Stephenson 
in England. Two of those British locomotives were 
brought to Lowell for that particular purpose, a heavy 
and a light model. Francis' first job was to make 
pattern drawings of every one of their cast parts so 
that castings could be produced for use on the Amer?
ican counterparts thereof. When in 1837, Whistler 
left Lowell to finish the earlier work he had started 
on the Providence and Stonington Railroad, Francis 
remained behind. Therefore, he was present at Lowell 
in 1841 when Baldwin, Whistler, and Storrow began 
measuring the discharges in those canals. 
The method these engineers adopted for measuring 
those discharges was identical, in every respect except 
one, to that which the former preceptor of the Little?
ton Academy, Ithamar A. Beard, had used some ten 
or more years earlier on the Hamilton Canal. The 
exception was found necessary because there were 
considerably larger volumes of water involved than 
could be handled by a single measuring wheel. They 
solved that problem by widening the measuring sec?
tions in the canals, and stringing as many sixteen-
foot-diameter, ten-foot-wide wheels (with piers be?
tween each) as were needed onto a common shaft. 
Seven wheels (the largest number) were used on the 
Western Canal (Figure 32). 
Francis, who had kept the records for this project, 
and who saw to it that the instructions of the Com?
missioners were carried out, did such a good job 
thereon, that at least two members of the Commission 
recommended that he be placed in charge of the 
32 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 
future hydraulic work of the organization. It seems pursued that subject diligently, and ultimately be-
likely that the experience he acquired in hydraulics coming one of the nation's most highly respected 
on this occasion is largely responsible for his having hydraulic engineers of his generation. 
FIGURE 32.?Discharge measurement of the Western Canal in Lowell, Massachusetts, as con?
ducted in 1841-1842 by Baldwin, Whistler, and Storrow. (Drawn by John Allcott and A. H. 
Frazier.) 
NUMBER 28 33 
TUBING APPLICATIONS 
It has been mentioned previously that adjutages 
extending through the walls of Rome's water-supply 
reservoirs had cross-sectional areas of various mul?
tiples of "quinariae," and that such areas were the 
accepted unit of measure for the amount of water 
delivered to a consumer. They represented the earliest 
known use of tubing for measuring the flow of water. 
Without supplementary data, such as the head of 
water above them, and suitable mathematics, this 
"quinaria" method was, to put it mildly, extremely 
erratic. Despite its faults, however, the method per?
sisted to modern times. In fact it was still common 
practice in America during the late 1800s to measure 
flowing water by its modern equivalent, the "square 
inch." 48 
The Pitot Tube 
During the two thousand years between 300 B.C. 
and A.D. 1700, many studies had been made on how to 
evaluate the flow of water through pipes, orifices, 
sk 
FIGURE 33.?Henri de Pitot and his tube. (Portrait from Rouse and Ince, History of Hydraulics -
sketch by A. H. Frazier after description by Pitot, "D'Une machine pour mesurer la vitesse des 
eaux courantes") 
34 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 
nozzles, etc., but it was not until near the end of that 
period that significant progress was made. In 1732, 
Henri de Pitot (1695-1771) (Figure 33) introduced 
his "tube" which, although it was especially intended 
for use in open channels, became useful in closed con?
duits. His paper thereon was presented before the 
French Academie Royale des Sciences, Paris, on 12 
November 1732.49 
The original device consisted merely of two slender 
glass tubes mounted side by side onto one of the three 
flat surfaces of a triangularly shaped wooden rod. The 
lower inch or two of the first tube was bent at 90 
degrees to allow it to point directly upstream while the 
main portion thereof was held vertically. The second 
tube was straight throughout its entire length, with 
its lower end at the same level as the bent section of 
the first tube (Figure 33) . 
Water entering the open end of the bent tube would 
cause the column of water in that tube to rise above 
the level of the water in the surrounding stream as a 
result of the kinetic energy in that filament of water 
being converted into a pressure head. No correspond?
ing rise would take place in the straight tube. The 
differences in the elevations of water in those two 
tubes accordingly became a function of the velocity 
of the oncoming water. 
Rouse has translated a comment by Pitot about his 
invention as follows: 
The idea of this machine is so simple and natural that the 
moment I conceived it, I ran immediately to the river to 
make a first experiment with a glass tube, and the result 
confirmed completely my anticipation. After this first experi?
ment, I could not imagine that such a simple and at the 
same time very useful thing could escape so many skilled 
people who have written and worked on the motion of 
water.50 
Pitot's method of computing the velocity from the 
readings obtained from his tubes was not entirely like 
that presently in use, but it at least led the way to 
more accurate methods. 
As is true of almost every invention, later experi?
menters attempt to improve on their predecessor's 
device. For example, Henri P. G. Darcy, circa 1858, 
replaced the straight tube with one on which the 
lower end was bent 90 degrees in the downstream di?
rection. This caused a draw-down to occur in the 
elevation of its column of water, thus doubling the 
reading made on the scale, and reducing probable 
errors entering into such readings. The invention, 
however, still retains its original characteristics and 
Pitot-type tubes are commonly used today in hydraulic 
FIGURE 34.?A Pitot tube intended for use in hydraulic 
laboratories. This model was originally owned by the Prop?
rietors of Locks and Canals of Lowell, Massachusetts. 
(NMHT 314776, Smithsonian photo 74335.) 
NUMBER 28 35 
laboratories (Figure 34) with only slight modifica?
tions. The tubes are made of metal, rather than glass. 
Since this material is not transparent, it is impossible 
to read the height of the water column directly; 
flexible tubes are connected from the metal tubes to 
a nearby manometer, from which the readings are 
made with greater facility and accuracy. 
Although current meters of the conventional type 
have been found more practical for use on rivers, 
Pitot tubes have several characteristics that are advan?
tageous for laboratory work and for certain special 
applications. For example, no timing is required in 
connection with an observation; they disturb the 
natural flow of the water much less than most other 
devices; and they are capable of collecting data from 
a much smaller point in the cross-section of the 
stream. 
The Bentzel Velocity Tube 
The Bentzel velocity tube was developed in 1932 
by Carl E. Bentzel, then Research Assistant at the 
U.S. Waterways Experiment Station at Vicksburg, 
Mississippi. Three different models thereof, as manu?
factured in the 1940s by Leupold and Stevens, Inc., 
are shown in Figure 35a. Like the Darcy model, both 
tubes are bent at their lower ends, with one pointing 
upstream, the other, downstream; but differ in that 
they arc connected at the top so that the water can 
/ 
FIGURE 35.?a, Three models of Bentzel velocity tubes as manufactured in the 1940s by Leup?
old and Stevens, Inc.; b, sample rating curves for a Bentzel velocity tube. (From Leupold and 
Stevens catalog, ca. 1940) 
36 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 
flow upward through the front tube and continue 
downward through the other. At some point along 
that path is a long tapered glass tube within which 
the water-velocity has to vary (inversely) with the 
increase in diameter. A tiny loose float, slightly heavier 
than water, rests at the bottom (narrower) end of 
that tube when the instrument is submerged in still 
water; but when it is in flowing water, the float 
is pushed upward by the oncoming water until a 
balance occurs between the velocity and gravitational 
forces acting on it. Upon its arrival at that resting 
point, the operator reads its height on an adjacent 
scale, and converts that reading into a corresponding 
velocity value obtained from a rating of the instru?
ment. 
Another model based on this same idea has an 
inverted tapered section and a float that is lighter 
than water. The float tends to remain near the top 
of that section until pushed downward by the oncom?
ing water until the equilibrium point is reached. A 
similar rating is needed to convert that point, as read 
on the scale, to the appropriate velocity value. Instru?
ments such as this are discussed at considerable length 
in the chapter on "Variable Aperture Flow Meters" 
in Troskolanski's Hydrometry.51 
A variation on the use of tubing in current meters 
is of historical interest, though it was not in the main 
line of development. On 31 August 1806, Vittorio 
Fossombroni had presented, in behalf of Francesco 
Focacci (fl. 1806), a paper before the Italian Aca?
demy of Sciences. It was entitled, "Per Investigare la 
Celerita' Dell'Acque Correnti," and contained a re?
port on the distribution of water velocities in a canal, 
as investigated by Focacci with his two current meters 
(Figure 36). It will be seen that horizontal tubing had 
been used as parts of both models, a unique applica?
tion for such instruments. 
One (Figure 36a) contained, in the box below the 
a 
4P;^-- V ?';?':'-
1/4/ 9, 
' 
^^ 
FIGURE 36.?Focacci's two current meters, 1806: a, balance scales are used to measure the force 
required to open the flap valve within the submerged box; b, pointer enables the operator to 
count and time the revolutions of the rotor within that instrument's box. Bottom of 6 is a ver?
tical-velocity curve of the canal being studied, the earliest known publication of such a curve. 
(From Focacci, "Per Investigare la Celerita' Dell'Acque Correnti," page 396, plates 11, 12.) 
NUMBER 28 37 
water surface, a flap valve that covered the inner end 
of the dowstream tube. Observations were made of 
the minimum weight necessary on the pan of the bal?
ance in order to open that valve. A comparison of 
this model with Darcy's version of the Pitot tube is 
of interest in that the weight required to open the 
flap valve (assuming the same size tubing were used) 
would be equal to the difference in weights of the 
two columns of water in the Darcy tube. In Focacci's 
meters, the force is a mechanical one, whereas in the 
other it is a hydraulic one. 
On Focacci's other instrument (Figure 36b), either 
a cup-type or an "S-type" rotor replaced the valve 
mechanism. The axle therof extended upward to the 
top of the apparatus where a pointer was fastened to 
it, which enabled the operator to count (and time) 
its revolutions. 
The Venturi Tube 
In 1797, Giovanni Battista Venturi [J. B. Venturi] 
(1764-1822), Professor of Natural History at Modena, 
published two works, entitled Essai sur les ouvrages 
physico-mathematiques de Leonard de Vinci and 
Experimental Inquiries Concerning the Principle of 
the Lateral Communication of Amotion in Fluids, both 
originally in French. The first brought to public at?
tention the wealth of scientific data (including hy?
draulics) in Leonardo's notebooks and focused interest 
on his achievements as a scientist, as distinguished 
from that of an artist?an interest that has never since 
abated. 
In 1837, the second of Venturi's publications was 
translated into English by a civil engineer, Thomas 
Tredgold, in his Tracts on Hyraulics. By means of 
laboratory equipment, such as was previously designed 
by the Marquis Giovanni Poleni, Venturi studied the 
manner in which water emerged from a constantly 
filled tank through different types of outlets. One such 
outlet of his own design, to which he had attached 
three manometer tubes, is shown along with Venturi's 
portrait in Figure 38. This particular design of the 
tube bearing his name, allows any volume of water 
flowing through water mains to be metered continu?
ously without using instruments that would interfere 
with the flow. 
Little or no effort was made to adapt Venturi's 
design to any practical apparatus until 1888, when an 
outstanding American hydraulic engineer, Clemens 
Herschel (1842-1930) exploited it to develop a device 
for measuring the amount of water flowing through 
pipes. In recognition of Venturi's experiments, Her?
schel named his device a "Venturi Tube." Tens, if 
not hundreds, of thousands of Venturi tubes are 
presently in use throughout the world. Herschel was 
Valve 
Rubber coupling 
Glass tube 
FIGURE 37.?The Venturi element (below) and manometer 
from Aggeler's current meter. (Redrawn by A. H. Frazier 
after Aggeler, "Design of a Venturi Type Current Me?
ter.") 
30 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 
SUPPLY 
TANK 
VALVL-X 
CONSTANT htAu TANK 
ENLARGED VIEW OF ThE VENTURI 
TUbE ON WhICh HE hAU INSTALLED 
THREE MERCURY MANOMETERS 
FIGURE 38.?Giovanni Battista Venturi and schematic of equipment used to test how rapidly 
the various types of outlets would permit filling of the lowermost (discharge) tank. The "win?
ner" (insert) was ultimately known as the "Venturi tube." (Portrait courtesy of Hunter Rouse-
schematic adapted from Venturi, "Experimental Inquiries.") 
NUMBER 28 39 
awarded a patent (U.S. 381,373) for it on 17 April 
1888. His photograph, and a photograph of the first 
commercial model thereof (built for use in a water 
main in Newark, New Jersey, in 1892), are presented 
in Figure 39. 
Inevitably, someone was bound to devise a current 
meter embodying the principles discovered by Venturi. 
Several of these meters are known, but only the first 
thereof is described here. It was conceived in 1926 by 
one Cecil Aggeler, then an engineering student at the 
University of California. His bachelor's thesis was 
FIGURE 39?Clemens Herschel and his first commercial 
model of the Venturi tube. (Courtesy of Steponas Kolu-
paila.) 
IvN FOU5J 
40 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 
FIGURE 40.?Ralph Leroy Parshall 
and plans of his improved Venturi 
flume. (Portrait courtesy of Step-
onas Kolupaila; plans from Par-
shall, "The Improved Venturi 
Flume") 
entitled, "Design of a Venturi Type Current Meter." 
The device consisted on an 8-inch-long cast aluminum 
tube with a Venturi-shaped opening through the cen?
ter. The hollow space between its inner and outer 
walls was divided into two compartments, one of 
which communicated with the water flowing through 
the throat of the Venturi, the other with the water 
near the entrance thereof. The handle consisted of 
two small-diameter pipes which were connected, res?
pectively, with each of those compartments. Glass 
tubes forming a manometer were fastened onto the 
tops of those pipes, and the water was drawn up to 
the elevation at which readings could be made of die 
relative heights of the two columns by evacuating 
most of the air in those pipes. 
Drawings of that manometer and of the Venturi 
portion of this apparatus, appear in Figure 37. 
Between 1915 and 1926, Victor Mann Cone 
(1883-?), Carl Rohwer (1890-1959), and Ralph 
Leroy Parshall (1881-1959), all irrigation engineers 
of the U.S. Department of Agriculture, and con?
nected more or less consecutively with the Colorado 
Agricultural Experimental Station at Ft. Collins, each 
wrote articles promoting the use of Venturi-type 
flumes for measuring the volume of water flowing in 
irrigation ditches. The most successful of such flumes 
was designed by Parshall (Figure 40) and was des?
cribed in his article, "The Improved Venturi 
Flume." 52 
Such flumes have been built in all sizes ranging 
from large permanent concrete or wooden flumes, in?
tended for obtaining continuous records of the flow 
in large canals, to small portable sheet-steel models, 
which some hydrographers carry about like current 
meters for making measurements of very small 
streams. Perhaps the most up-to-date discussion on 
mis subject is in Technical Note No. 117: "Use of 
Weirs and Flumes in Stream Gauging," published in 
1971 by the World Meteorological Organization, a 
specialized agency of the United Nations. 
NUMBER 28 41 
THE LONGITUDE CONTEST 
In 1714, several captains of her Majesty's ships, 
merchants of London, and commanders of merchant?
men, presented a petition to the House of Commons, 
claiming that a method for discovering the longitude 
of ships while they were at sea was of extreme import?
ance to Great Britain for the safety of its Navy, its 
merchant ships, and for the improvement of its trade. 
For want of it, they contended, many ships had been 
delayed in their voyages, and many lost; and some 
persons might conceive of suitable methods and 
prove them before the proper judges. A committee 
was accordingly established to consider the subject. 
Among those who presented evidence before that 
committee was Sir Isaac Newton. He suggested that 
large sums of money be offered for the most accept?
able solutions. In consequence thereof, Parliament 
passed an Act "for providing a Publick Reward for 
such Person or Persons as shall discover the Longitude 
at Sea. 12 Anne. Stat. 2. cap. 15." 53 The amount of 
the reward was graded in amount according to the 
degree of accuracy achieved: 
?10,000 for a method accurate within 1 degree of longitude, 
?15,000 for accuracy within 40 minutes, 
?20,000 for accuracy within 30 minutes.04 
The administration of this statute was entrusted to 
commissioners known as the Board of Longitude. 
De Saumarez' Ships' Logs 
Among those who entered the contest was one Hen?
ry De Saumarez (fl. 1715), a member of one of the 
most prominent families on the Island of Guernsey. He 
failed to win any of the prizes, but he did accomplish 
much of historical interest. (No award whatsoever 
was made until 1762, when John Harrison obtained 
the maximum prize for the performance of his No. 
4 marine timepiece on a voyage to Jamaica.) The De 
Saumarez entries consisted of two radically different 
types of ships' logs which he called "Marine Survey?
ors" (Figure 41) . He described them as having been 
"contrived for the mensuration of the way [velocity] 
of a ship in the sea more correctly than by the log or 
any other method used for that purpose." 55 Although 
not mentioned in his claims, his logs were also used as 
current meters for measuring the velocity of the water 
flowing in rivers. 
The Log with a Vertical Axis 
There is a practice presently in vogue of dividing 
current meters (and ships' logs) into two major cate?
gories, namely those which have vertical axes, and 
those which have horizontal axes. Although De Saum?
arez' 1715 models bear very little resemblance to their 
modern counterparts, both of them fall within those 
categories.The model with the vertical axis appears 
in Figures 41a, b. Its rotor has four spokes at the ends 
of which he had fastened (by means of hinges) flat 
pallets arranged in such a manner that the oncoming 
water would strike against their broad flat surfaces 
during the "driving" phase of its revolution; but dur?
ing the remaining portion of that revolution, it would 
strike against only the narrow edge of the pallet. The 
unequal forces thus created would produce the desired 
rotary motion. A replica of this rotor, from the Smith?
sonian collection of current meters, appears in Fig?
ure 42. 
De Saumarez obtained King George I's permission 
to perform experiments with his "machine" on the 
quiet waters of the canal in St. James Park in London. 
There he became satisfied that the rotor would make 
one revolution while the boat traveled a particular 
distance, regardless of the speed at which the boat was 
moving. After having satisfied himself in that respect, 
he adjusted the length of the spokes on the rotor until 
ten feet of travel would produce exactly one com?
plete revolution. 
Whether this principle of operation was borrowed 
from some previous invention, or rediscovered inde?
pendently by De Saumarez is not known. It is known, 
however, that Edme Mariotte had described an old 
Chinese windmill that operated on much the same 
principle. Figure 43 depicts a model of either an an?
emometer or a windmill which also operates on this 
principle.56 It may be noted from Figure 41a that a 
large dial constituted an important part of this equip?
ment. De Saumarez explained its purpose as follows: 
A Dial, which being placed anywhere on Board of a Ship, 
will by Correspondence with a small Wheel moving under 
Water, and a little Bell striking with the said Dial, curiously 
42 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 
v/?//{\\c//W//S. /cV>'. 
FIGURE 41.?De Saumarez' ships' logs: a, b, vertical-axis model; c, d, horizontal-axis model. 
(From De Saumarez, "III. A Further Account of a New Machine," figures 1-4.) 
NUMBER 28 43 
demonstrate the Geometric Paces, Miles, or Leagues which 
the ship hath run; which being applied in a proper manner, 
will be of little or no Hindrance to the Course or Sailing of 
the Ship. The said Wheel shall turn in any depth of the Sea, 
so that no storm, nor rough Sea, nor the violent Motion of 
the Ship will alter, hinder, nor stop the regular Working 
thereof, but the Swiftness and Slowness of the Ship shall be 
seen and heard by the striking of the little Bell in the said 
Dial." 
Some of the difficulties that De Saumarez encount?
ered in his effort to get the authorities to give con?
sideration to his entries in the "longitude contest" will 
be described later (pp. 46-47). Although that effort 
was not successful, a considerable amount of discus?
sion, including illustrations of his devices, appeared 
later in volumes 33, 34, and 36 of the Philosophical 
Transactions of the Royal Society of London" 
One of the articles {Philosophical Transactions, vol?
ume 34) contains several tables showing the speed of 
the currents in the Thames Estuary as the tides ebb 
and flow therein. Two pages of those tables appear in 
Figure 44. De Saumarez obtained the data for those 
tables with his vertical-axis current meter. The tables 
are believed to contain the first of such velocity data 
ever to have been published. 
v^iiu 
FIGURE 42.?Replica of De Saumarez' rotor, which was used 
on his vertical-axis ships' log, ca. 1715. (NMHT 321481, 
Smithsonian photo 75593.) 
FIGURE 43.?A sketch of an instrument that appears in a 
painting entitled, The Paris Academy of Science?A Visit by 
Louis XIV. This device, a forerunner of De Saumarez' ships' 
logs, was doubtless a model of either a windmill or an an?
emometer. (Redrawn by A. H. Frazier, from Wolf, A His?
tory of Science, opposite page 63.) 
Finding a correct designation for the type of rotor 
used on De Saumarez' vertical-axis model has not met 
with too much success. An article by Arthur T. Saf?
ford, a former Engineer of the Proprietors of Locks 
and Canals at Lowell, uses an expression, "flutter 
wheel" 59 to describe a mill wheel that seemed to 
operate on the same principle. It seems to fit the De 
Saumarez device, but it is not confirmed in the third 
edition of Webster's New International Dictionary. 
The Log with a Horizontal Axis 
One of the difficulties encountered with the vertical-
axis equipment was a tendency for weeds and fibers 
to become entangled with the rotor. To overcome diis 
44 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 
( h ) 
III. A T A B U L A R Account, fhewing the Strength 
and gradual Increafe and Decreafe of the Tides of 
Flood and Ebb in the River Thames, as obferv'd 
in Lambeth Reach, off of Mancbefler Stairs, and 
in the Middle of the River, with a new Jnfrru-
ment call'd the Marine Surveyor, on the yth of 
June, 1720, It being then Full Moon, and con?
sequently a Spring Tide. The Movement of the 
Machine 14 Inches under Water. 
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FIGURE 44.?Data compiled by Henry De Saumarez with his vertical-axis ship's log, showing 
the velocities in the Thames Estuary at the ebb and flood tides on 8 June 1720. These are the 
earliest known published data of this nature. (From De Saumarez, "IV. Observations upon the 
Tides in the River Thames," pages 69-70.) 
tendency De Saumarez designed a horizontal axis 
model, which, shaped like a capital "Y" and towed 
through the water by means of a rope connecting the 
lowermost end of the "Y" to the dial aboard the 
ship, shed itself of such unwanted debris. Curved 
metal plates on the outer arms thereof caused the unit 
to revolve about its central axis as it was drawn 
through the water. The curvatures of those plates 
were so adjusted that the speed of its revolution would 
be the same as on the vertical-axis model, namely one 
revolution for every ten feet of travel, so the same dial 
facilities could be used on both models. 
At very low velocities, however, the rotor of the 
horizontal axis model would tend to sink lower and 
lower into the water?the slower the speed, the deeper 
it would sink. This tendency is represented by the 
several positions shown of the rotor in Figure 4 I t . 
The objection was that as the horizontal angle of the 
rotor increased, it tended to register lower velocities 
than it should. Under most conditions, however, this 
fault was not present. De Saumarez found various 
other practical uses for this equipment, such as to ob?
tain data for a navigation chart showing the locations 
and magnitudes of the velocities occurring in the Eng-
NUMBER 28 45 
f- ? ? ? 
FIGURE 45.?A fleet of ships, ca. 1725, all equipped with De Saumarez' horizontal-axis ships' 
logs, purportedly gathering data on the currents in the English Channel. (Courtesy of the British 
National Maritime Museum.) 
lish Channel. Such a chart, bearing the signature of its 
probable original owner, Captain Bligh of the Bounty, 
has been preserved in the British National Maritime 
Museum, Greenwich. At the top thereof is a painting 
showing a fleet of ships (Figure 45) , all equipped 
with "Marine Surveyors," purportedly obtaining data 
for that purpose. A replica of the horizontal-axis rotor 
(Figure 46) is in the Smithsonian collection. 
John Smeaton, the famous British engineer who 
built the noted Eddystone Lighthouse, had not yet 
been born at the time most of the above events were 
taking place. He studied, however, the De Saumarez' 
discussions of his ships' logs in the Philosophical Tran?
sactions,60 and proposed what he thought would be a 
major improvement. His paper thereon was read be?
fore the Royal Society of London on 4 April 1754.61 
His plan replaced the 27-inch-long Y-shaped rotor 
and its stout cord, with a simple flat piece of brass, 
10 inches long and 2'/2 inches wide, twisted into such 
a shape that it rotated in much the same manner as 
the original rotor. Because of its much smaller dimen?
sions and weight and of the use of a much lighter and 
more slender cord, the drag forces and, consequently, 
the friction in the bearing that had to carry the load 
was greatly reduced?so much so in fact, that a differ?
ent and much more efficient type of bearing could be 
used. Smeaton tested his apparatus in the serpentine 
river in Hyde Park, London, in much the same man?
ner that De Saumarez had made his original tests. 
A replica of Smeaton's rotor is in the Smithsonian 
collection (Figure 47) . 
Apparently this idea did not prove to be as much of 
a success as Smeaton had hoped, because no mention 
of it can be found in later records. 
46 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 
FIGURE 46.?Replica of the rotor used on De Saumarez' horizontal-axis ships' logs, ca. 1716. 
(NMHT 321480, photo by A. H. Frazier.) 
FIGURE 47.?Replica of the rotor John Smeaton proposed, ca. 1754, as an improvement over 
the Y-shaped De Saumarez model. (NMHT 321482, photo by A. H. Frazier.) 
Administrative Strategy, 1716 Style 
From what has been reported thus far about De 
Saumarez' ships' logs, it might be assumed that all 
of the problems he had experienced with them were 
of a mechanical nature. Those, however, which he 
encountered with the men concerned with "discover?
ing the longitude" were much more frustrating. In 
1717 he published a 17-page pamphlet setting forth 
his experiences with them.02 It revealed that his dis?
covery had been offered to, and that he had been 
graciously received by, His Majesty, the King, but 
that it had not been "so well encouraged by some of 
those appointed to examine and inquire into the 
same." U3 The King had suggested that he present his 
idea to the Royal Society of London for them to 
evaluate its merits. He accordingly visited Edmund 
Halley, of Halley's Comet fame, who was then Secre?
tary of that society. Halley entertained him at his own 
house "in several friendly conferences" before De 
Saumarez presented his petition, but the Royal Society 
itself did not respond so cordially. It replied in effect 
that: (1) They did not conceive that the decision 
belonged to them; (2) it was not a new discovery; 
NUMBER 28 47 
and (3) the amount it would hinder the ships prog?
ress would not be compensated for by its anticipated 
advantages. 
In December 1715, De Saumarez returned again 
to the King who, on this occasion, referred him to the 
Lords Commissioners of the Admiralty. They, as of 
7 January 1716, referred his petition to Sir Isaac 
Newton, who was then President of the Royal Society. 
He, as of 27 January, submitted the following report 
to the Admiralty Office: 
Sir, 
According to the Order of the Lords Commissioners of the 
Admiralty, I have considered the inclosed Proposals of Mr. 
Henry de Saumarez, and discoursed with him upon the same, 
and am humbly of the opinion that by means of the Instru?
ment he hath invented a Reckoning of the distance Sailed by 
a Ship may be kept with less trouble than by the Logg-Line, 
but I am not yet satisfied that the Reckoning will be so 
exact. The Instrument now proposed will keep a Reck?
oning of the Motion of the Ship with respect to the upper 
part of the Sea Water, but not of the driving of the Ship 
by Currents and Tides, and by the Motion of the upper 
Surface of the Sea caused by Winds, and how far it will keep 
a true Reckoning of the Motion of a Ship side Ways, oc?
casioned by a side Wind, doth not appear to me, and there?
fore the Logg-Line is not to be laid aside . . the Logg-Line 
alone should be depended upon, until it appears by Experi?
ence how far this New Instrument may be trusted. I have 
no Experience in Sea Affairs, nor ever was at Sea, and there?
fore my Opinion is not to be much Relied on. 
[signed! Is. Newton 
To quote De Saumarez: "The Lords of the Ad?
miralty finding that Sir Isaac declined to give a deci?
sive opinion they were pleased to put it into the 
hands of the Gentlemen of Trinity House." 63 After 
due consideration, that corporation prepared a list 
of objections to which De Saumarez responded on 14 
April 1716. After considering that response, they sent 
a report to the Lords Commissioners of the Admiralty, 
dated 8 May, which stated bluntly that "the Corpora?
tion is of the opinion the same is wholly impractic?
able." GG 
The Commissioners took no immediate action on 
that report. In fact, De Saumarez could not even get 
a copy of it, or information regarding its contents 
until 8 June. Then, upon finding what it contained, 
he attempted to obtain a patent on it, with the in?
tention of building models at his own expense. He 
was told at the Patent Office, however, that no patent 
could be awarded thereon until the Lord Commission?
ers of the Admiralty submitted a report to the King, a 
procedure which they appeared reluctant to do. 
On 5 July 1716, De Saumarez petitioned the Com?
missioners to report to the King in order that he, De 
Saumarez, would not be "hindered" from proceeding 
with the project on a personal basis. They thereupon 
forwarded immediately to the King the report they 
had received from Trinity House, stating that "we 
have nothing further to add thereto." G7 
The concluding chapter of De Saumarez' pamphlet 
is headed: "Upon all which, the following observa?
tions are humbly offered." The chapter contains only 
five paragraphs, the most succinct of which states in 
effect that if he had been treated as promptly and 
respectfully by the gentlemen of the Trinity House as 
he had been by the Royal Society, he might in less 
than half an hour, have been saved a great deal of 
pains, loss of time, costs, and charges, and returned 
home where he "might have taken other measures." 
De Saumarez did indeed build several models and, as 
already explained, used them for studying the veloci?
ties in the Thames Estuary, and for charting those in 
the English Channel. 
-18 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 
HORIZONTAL-AXIS METERS 
Early European Developments 
Robert Hooke 
Robert Hooke (1635-1703), the author of Hooke's 
Law of Elasticity, and the first Curator of Experi?
ments at the Royal Society of London, was a man of 
extraordinary talents. Several writers have ranked 
him second only to Leonardo da Vinci insofar as 
inventive ingenuity and conceptual creativity are con?
cerned. Like Leonardo, one of the devices he con?
ceived was intended for measuring the velocity of 
r&JZ *~*~ *ffo s~>j ^ * *?i 
-^H? /& u>y y -? ** 
i*. ~*./*? &?/ ->f 
FIGURE 48.?Hooke's report on a ship's log. (Photocopy from Register of the Royal Society of 
London, volume 6, pages 84-85; courtesy of the Royal Society of London; transcription by A. H. 
Frazier.) 
flowing water. His model was considerably more 
sophisticated than Leonardo's in that it was provided 
with a velocity-sensing mechanical rotor, quite similar 
to those on modern current meters of the horizontal-
axis type. He used rotors of that same type in at least 
three different applications: the current meter, a deep-
sea sounding facility, and on a ship's log which he 
called "A Way-wiser for Sea" (Figure 48).C8 Figure 
49 illustrates the rotor described in Figure 48 as the 
"Vane, Fly, or first mover of the whole." 
A WAY-WISER FOR SEA 
November the 28th, 1683 
I shewed an instrument I had contrived 
and shewed some of the Society about 20 
years since by which the way of a ship 
through the sea might be exactly measured 
as also the velocity of any running Water 
or River and thereby the comparative velocity 
of it in its several parts, by this also the quantity 
of the water vented by any River into the Sea 
or any other River might be found. Tt was 
one part of a way wiser for the Sea. The 
whole Engine being designed to keep a true 
Account not only of the Length of the Run of 
the Ship through the water, but the true Rumb 
or Leeward way, together with all the Jackings 
and workings of the Ship. This part of the Engine 
now shown was the Vane, Fly, or first Mover 
of the whole, feeling as it were & distinguishing 
the several Qualifications of the Ship's Course, 
but was to be regulated by several other 
Additions in the completed Engine which I 
designe shortly to get executed. 
NUMBER 28 49 
A 
FIGURE 49.?Author's reconstruction of rotor that Robert 
Hooke used on his current meter, sounding device, and ship's 
log. (Drawn by A. H. Frazier.) 
Although Hooke's current meter was not respon?
sible for starting the present vogue for horizontal-axis 
meters, it represents the earliest of any devices of that 
type to have been found so far. 
The second meter of the horizontal-axis type to 
have received any appreciable attention, was the one 
previously made by Henry De Saumarez. That too, 
failed to make any lasting impression or attract any 
appreciable number of followers. 
Reinhard Woltman 
Considerably more than a century after Robert 
FIGURE 50.?Replica of the Woltman current meter, ca. 
1790. (NMHT 317671, Smithsonian photo 72259.) 
50 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 
Hooke produced the first of the horizontal-axis-type 
current meters, Reinhard Woltman (1757-1837), who 
in 1784 was in charge of hydraulic operations at 
Cuxhaven, Germany, produced one that started the 
present vogue (particularly in Europe) of building 
current meters in that manner. It seems unlikely that 
Woltman had known about either the Hooke or the 
De Saumarez meters, but the principle of his rotor, 
and his use of a worm gear arrangement for counting 
the revolutions were very similar to those conceived 
by Hooke. 
In 1790, Woltman published a booklet entitled 
Theorie und Gebrauch des Hydrometrischen Flugels, 
describing his new meter. It explains how he built an 
anemometer, after which he was faced with many 
problems about "rating" (i.e., calibrating) it. After 
several false starts, he finally rated it successfully in 
still water. This gave him the idea that by reducing 
the overall diameter of the rotor from about one meter 
to about one foot, the modified device would serve 
excellently as a water current meter. A replica of this 
water current meter (Figure 50) is presently in the 
Smithsonian collection. 
Julien John Revy 
Julien John Revy (fl. 1870), an Austrian by birth, 
but a resident of England in his later years, was a 
civil engineer of considerable importance. In 1857 he 
was the Director of the Martienson Machine Factory 
in England. Later he became a member of the Aus?
trian Institute of Civil Engineers, and from 1869 to 
1878 (probably the date of his death) he was a mem?
ber of the British Association for the Advancement 
of Science. In that association's Annual Report for 
1862 is a description of his bold plan for constructing 
a vehicular tunnel, lined with cast iron pipes, beneath 
the English Channel. His most important written work 
was his report on the Hydraulics of Great Rivers: the 
Parana, the Uruguay, and the La Plata Estuary. In 
it he describes how the discharges of those streams 
were measured under his supervision for the British 
Admiralty. In view of the fact that the La Plata 
Estuary alone is at its narrowest over twenty miles 
wide, this must have been the most ambitious stream 
gaging project of all time. 
Many pages of Revy's book are devoted to the faults 
he found with the use of floats for measuring water 
velocities. Current meters, properly handled, he 
claimed, could produce far more accurate results. Be?
fore leaving England to start work on that project, 
he had a current meter of his own design built. As 
his work in South America progressed, he kept alert 
for any changes by which it might be improved. His 
final design (arrived at after the project had been 
completed) became a regular stock item with the firm 
of Elliott Bros, (successors to Elliott & Sons) in Lon?
don, and was listed along with Saxton's meter m 
several editions of their catalog. 
American establishments that purchased at least 
one of the Revy meters were the United States Geo?
logical Survey, and the Coast and Geodetic Survey, 
both of which contributed their models to the Smith?
sonian Institution. A photograph of the one originally 
owned by the Geological Survey is shown in Figure 51. 
Among the innovations Revy introduced in his new 
current meter were the following: 
1. The rotor was so designed that it would have 
no weight when submerged in water. The 2-inch ball 
at the center thereof was filled with air, and had just 
enough buoyancy to make the overall specific gravity 
of the rotor-and-shaft assembly equal to that of water. 
The purpose was to reduce the weight (and conse?
quently the friction) on the bearings which supported 
those parts. 
2. The compartment within which the counting 
gears were located, was filled with clean water, there?
by preventing sand, grass, or other materials from 
becoming lodged between the gear teeth and slowing 
down the normal speed of the rotor. 
3. Although Revy used a vertical bar to support the 
meter when using it in relatively shallow water, he 
suspended it from a long horizontal metal bar when 
making velocity measurements in deep water. On such 
occasions it was suspended from a surface vessel by 
means of two wires, one at each end of the vessel sup?
porting the corresponding ends of the horizontal bar. 
(This method has come to be known as the "bi-filar" 
method of suspension.) The arrangement greatly re?
duced the tendency of the meter to swing like a 
pendulum when operating at great depths, and it 
provided better control of the apparatus while ob?
taining average velocities by the "integration" method. 
The "integration" method consisted of lowering 
the meter slowly to the bottom, and then raising it to 
the surface at the same speed, with the counting gear 
engaged throughout the entire period of the "run," 
with the time required to make that run, carefully 
determined. The results thus obtained would be the 
NUMBER 28 51 
FIGURE 51.?The Revy current meter, manufactured by El?
liott Bros., London, ca. 1874. (NMHT 289646, Smithsonian 
photo 44538-C.) 
average, or integrated velocity throughout the ver?
tical at that point in the stream. It was, as a matter 
of fact, the only method that could be applied with a 
"bi-filar" suspension system, because it was not pos?
sible to manipulate a third wire or cord properly for 
engaging or disengaging the counting gear on the 
meter. Point observations could only be obtained with 
this meter when it was suspended from a vertical rod 
or bar, but the maximum depth at which such a bar 
could be handled even when the velocities were mod?
erate was quite limited. 
Revy's current meters?in fact all current meters 
having a similarly geared counting arrangement? 
were eclipsed in popularity with the advent of Henry's 
electrical contact facility, which, as will be described, 
reduced the amount of friction in meters, eliminated 
the need for the operator to raise the meter to where 
he could make "before" and "after" readings of the 
dial for each run, and allowed either "point" or "in?
tegrated" observations at any depth without any loss 
of time or any changes in his equipment. 
Joseph Saxton 
Joseph Saxton (1799-1873) the first and most out?
standing American to invent a current meter, has in 
the past received perhaps the least attention of any 
such inventors. The story of his life would have been 
a fitting subject for Horatio Alger. He was a descen-
dent of George Sexton who came to America in about 
1663 and lived first near Windsor, Connecticut, and 
then at Westfield, Massachusetts. Subsequent mem?
bers of his family line lived successively at Hunting?
ton, Long Island; Hopewell, New Jersey; Frederick, 
Maryland; and finally, at Huntingdon, Pennsylvania, 
where Joseph was born 22 March 1799. His grand?
mother was Sarah Harlan of the same family of Har-
lans from which the two Justices of the United States 
Supreme Court descended, and his brother John was 
the founder of the still-active newspaper, Akron 
(Ohio) Repository, and the grandfather of Ida Sax?
ton McKinley, wife of the martyred President. 
Joseph left school at the age of twelve to begin 
working at his father's nail factory. That work soon 
lost its appeal, and he was apprenticed to a local 
watch-maker. During that apprenticeship, he learned 
the importance of precision workmanship, and the 
subject fascinated him. To constantly improve his 
talent in that field became a primary goal of his 
career. Upon the death of his employer, the nineteen-
year-old Joseph left Huntingdon for Philadelphia. 
That city, then the science center of America, seemed 
to offer further opportunities for achieving his goal. 
In 1824, the Franklin Institute in Philadelphia was 
established, and Joseph was among its early members. 
During that same year, the Institute held its first 
public exhibition. Prizes were offered for many classes 
of entries, and one of the local clock dealers entered 
a clock into that competition which Saxton had built 
52 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 
for him. The clock was unusual in two special res?
pects: the pallets on its escapement did not have to 
be kept oiled, and it had a unique type of tempera?
ture-compensated pendulum. Saxton received the 
highest award offered for such an entry, a silver 
medal.69 
One of the persons who judged that contest was 
Isaiah Lukens, one of Philadelphia's finest mechanics, 
a vice president of the Institute, and perhaps the 
leading manufacturer of tower clocks in the Philadel?
phia area. He took Saxton into his shop as an asso?
ciate, and within the next four years they built one 
of the three tower clocks that has occupied Philadel?
phia's historic Independence Hall. 
In about 1829, Saxton, still searching for oppor?
tunities to improve the precision aspects of his work, 
left Philadelphia for a seven-year sojourn in London. 
Just as Philadelphia was the American Mecca for 
those who wished to develop their scientific talents, 
London had become the world Mecca in that respect. 
A possible additional inducement that led Saxton to 
make the trip was the imminent completion there 
of a new museum officially called the "Gallery for the 
Illustration and Encouragement of Practical Science" 
(later abbreviated to the "Adelaide Gallery" because 
of its location at No. 7 Adelaide Street in the S t rand) . 
Contemporary observers described that gallery as 
both large and elegant?perhaps the most elegant in 
the metropolis (Figure 52) . The Gallery had original?
ly been intended to serve as a showplace for exhibiting 
FIGURE 52.?The "Long Room" of the Adelaide Gallery in London. In 1832, Saxton rated his 
current meter in the 70-foot-long tank of water shown in this room. (From the catalog of the 
Adelaide Gallery, May 1836.) 
NUMBER 28 53 
the steam boilers and other inventions of Jacob Per?
kins (1766-1849), an ingenious Philadelphian who, 
before moving to London in 1819, had been a 
manufacturer of fire engines with Coleman Sellers, 
one of Saxton's close friends. 
Whether Saxton had been assured in advance that 
he would receive work building permanent exhibits 
for that new gallery is not known, but it is well es?
tablished that promptly after his arrival, he received 
orders to build several of such exhibits. The work was 
performed at his newly established shop at 22 Sussex 
(now Huntley) Street, one block east of Gower, near 
the University College. After the Gallery opened on 
4 June 1832 he gave lectures there concerning those 
and other exhibits. 
During the mid-1830s, while Saxton was still at 
London, Franklin Peale, acting in behalf of the 
United States Mint, placed an order with him to build 
an assay balance. Tha t balance turned out so well 
that several more balances were ordered, and R. M. 
Patterson, then Director of the Philadelphia Mint 
offered him "a good job to begin with" if he would 
return to America and perform work for the Mint. 
Saxton accordingly returned to Philadelphia in 1837, 
and worked for the Mint until 1843, when A. D. 
Bache, then Superintendent of the United States 
Coast Survey, induced him to move to Washington, 
D . C , and assume charge of the Office of Weights and 
Measures, die forerunner of the National Bureau of 
Standards. While holding that position, Saxton fin?
ished building and delivering to those States not sup?
plied, a complete set of volumetric, lineal, and 
weight standards, together with a set of balance scales 
(one large, one medium, and one small) for use with 
those standard weights. It would seem that in building 
those precision standards for most of the States, Sax-
ton's goal in life had finally been achieved. He con?
tinued in that position until his death, 26 October 
1873. 
Among the many honors Saxton had received dur?
ing the course of his lifetime, were those of being 
selected a charter member of the National Academy 
of Sciences, and a member of the American Philoso?
phical Society. One of the "State" balances he had 
constructed was sent to the Great Exhibition in Lon?
don in 1851, for which he was awarded a gold medal. 
Saxton's first efforts in developing current meters 
came as a result of a purchase order from Joseph 
Cubitt?son of the prominent civil engineer William 
Cubitt (1785-1861)?while Saxton was working at the 
Adelaide Gallery in London. Saxton mentions some of 
the subsequent work on the meter in a diary, which 
is preserved in the Smithsonian Archives:70 
May 25, 1832. Saw J. Cubitt and Mr. Cooper [at the Royal 
Institution] who introduced me to Mr. Faraday. 
August 2, 1832. At work at a current meter for Cubitt. 
August 11, 1832. Went to 7 Adelaide Street. Made experi?
ment with the current meter. 
August 21, 1832 7 Adelaide Street.Saw there J. Cub?
itt and his sisters. 
August 23, 1832. At 22 Sussex Street. Finished current meter 
for Cubitt. 
When, in 1836, the gallery published its first issue 
of The Magazine of Popular Science, it contained an 
illustrated article entitled: "Description of the Cur?
rent Meter as Recently Improved by Mr. Saxton." A 
reproduction of those illustrations appears in Figure 
53. As may be seen in that figure, the rotor on this 
meter consisted of a flat piece of brass twisted into 
such a shape as to cause it to revolve when water 
moved through it. Whenever the "engaging" cord was 
held taut, the rotating shaft would cause the count?
ing wheel to start operating. Saxton "rated" his cur?
rent meter in the 70-foot-long water tank in the Long 
Room of the Adelaide Gallery (Figure 52) . The 
rating consisted of increasing or decreasing the 
amount of twist in the rotor until it would make ex?
actly one revolution for every foot the meter traveled 
through the still water in that long tank. 
In this connection it should perhaps be mentioned 
that Saxton, Charles Wheatstone (famed for the 
"Wheatstone Bridge" for making electrical measure?
ments), together with a John Martin and two other 
persons, made a measurement of the flow of the Colne 
River at Denham Point near London with Saxton's 
current meter on 22 June 1834, in accordance with 
a plan proposed by Martin for improving London's 
water supply.71 
During the 1830s there existed in London a firm 
by the name of Watkins and Hill that sold scientific 
instruments and laboratory equipment. After Saxton 
arrived in London, their catalogs listed several ar?
ticles that Saxton had designed and furnished to 
them. Saxton's current meter, however, does not ap?
pear in any of their few surviving catalogs. Neverthe?
less when that firm was taken over by the Elliott 
organization in the 1850s, it was listed in the catalog 
that showed the combined products of the two firms. 
An illustration of the meter also appeared in 1858 as 
"Fig. 129A" in the first edition of W. Davis Haskoll's 
book entitled The Practice of Engineering Field 
54 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 
a 
R 
f 4 
. i. 
~. * ? 
1 ' -
? 
:[ 
FIGURE 53.?Joseph Saxton's water current meter: a, top view; b, side and end views. 
(From Adelaide Gallery, "Description of the Current Meter.") 
Work, together with the following statement: "El?
liott's [i.e., Saxton's] Current Meter is a most useful 
instrument for ascertaining velocities, either a few 
inches below the surface, at the bottom, or at any 
depth between." 72 
In any event, the Proprietors of Locks and Canals 
of Lowell, Massachusetts, were among those who ac?
quired one of Elliott's models of the Saxton meters, 
and in 1956 they contributed it to the Smithsonian 
Institution (Figure 54) . 
Although Saxton's meter was never listed in any 
American manufacturer's catalog, quite a number of 
them were custom-built here, and they made appear?
ances in several unexpected places. One such appear?
ance is mentioned in the Humphreys and Abbot fa?
mous Report Upon the Physics and Hydraulics of the 
Mississippi River.73 Saxton's was the only current 
meter used in that study, whereas over 99 percent of 
the other observations were made with floats. On an?
other occasion, Professor William P. Trowbridge of 
the U.S. Coast Survey 74 attached two Saxton current 
meters (both pointing downward) onto a device he 
had invented in 1857 for sounding the depths of the 
ocean in places too deep to be reached with the con?
ventional line and weight. Their function was to 
measure the depth as the device descended to the bot?
tom. Upon arriving there, a detent locked their mo?
tion, so that upon raising the assembly, the operator 
could observe on the counting wheels the number of 
rotations made by their rotors and thereby compute 
the ocean's depth. 
Prior to the Civil War, Humphreys, Trowbridge, 
and Saxton were fellow employees in the U.S. Coast 
Survey, and were well acquainted. There seems little 
doubt but that all of these meters were built in the 
instrument shop of the Office of Weights and Meas?
ures, where the lineal, volumetric, and weight stan?
dards had been built under Saxton's supervision for 
NUMBER 28 55 
FIGURE 54.?Saxton's current meter as manufactured by Elliott & Sons, London. 
{NMHT 314772, Smithsonian photo 44536-A.) 
FIGURE 55.?The "Abbot" meter. (From Payson, "Current-Observations 
in San Francisco Harbor, California.") 
56 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 
the American States. 
Perhaps the most unexpected circumstances under 
which Saxton current meters were used occurred in 
1877 and 1878 when the federal government made a 
study of the hydraulic aspects of San Francisco Bay.75 
In his report on that study, Lt. A. H. Payson called 
them "Abbot" current meters. General Henry Lar-
com Abbot had provided them for use on that study 
after having redesigned certain parts to overcome the 
problems caused by using them in sea water. A draw?
ing of one of these meters, as it appears in Payson's 
report, is shown in Figure 55. 
Current meters were not accepted without contro?
versy, even by those who were the forerunners in 
hydraulic engineering. In Humphreys' and Abbot's 
report on the Mississippi River, it had been stated that 
double floats were superior to any other device for 
measuring water velocities.70 In 1868, when Daniel 
Farrand Henry of the U.S. Lake Survey ventured to 
invent and use current meters for measuring the out?
flow of the Great Lakes, both Henry and his superior, 
General William F. Raynolds were severely disciplined 
for having used meters for that purpose.77 Henry Ab?
bott, the co-author of Humphreys' Mississippi River 
report, expressed himself as follows in a subsequent 
report: "In my opinion, . . . instruments of this class 
are pretty toys, which have contributed more to retard 
the progress of discovery in the science of river hy?
draulics than any other one cause," 78 and for many 
years thereafter, Abbot and Henry debated this sub?
ject bitterly. 
One of the major improvements Henry had made 
on current meters was the electrical facility for count?
ing the revolutions made by the rotor. After having 
first installed such facilities on his Saxton current 
meter, and finding them to work successfully, he next 
applied them to the cup-type meters of his own in?
vention, the latter of which received favorable atten?
tion in several European technical magazines. 
In view of Abbot's opposition to the use of any cur?
rent meters, the advent of the "Abbot" meter at San 
Francisco ten years after his objections were pub?
lished, must have surprised many of those familiar 
with the acrimonious Abbot-Henry debates. More?
over, Abbot's meter consisted essentially of a Saxton 
meter furnished with an electrical contact, just as 
Henry had originally changed it. The only difference 
was that Abbot had enclosed the contact facilities 
within an oil-filled brass compartment intended to 
exclude die salt water from the area where the con?
tacts took place. 
If Abbot ever felt that his action represented any 
softening of his attitude toward Henry's work, he 
never admitted it publicly. 
The Baumgarten Meter 
Table I in Professor Kolupaila's Bibliography of 
Hydrometry is a list of "Significant Hydrometric Mea?
surements in the 19th Century." The third entry 
refers to measurements obtained of the Tiber River 
in Italy by Giuseppi Venturoli (1784-1846) starting 
in 1821, and the seventh entry refers to those obtained 
of the Garonne River in southern France by Andre 
Gustave Adolphe Baumgarten (1808-1856) starting 
in 1838. Venturoli was a professor of mathematics at 
the University of Bologna, and Baumgarten was an 
engineer at the Ponts et Chausees in Paris. In both 
Venturoli's book, Elementi di Mechanica e Hydraul-
ica, and Baumgarten's article, "Sur le moulinet de 
Woltmann . . . , " 79 the same type of current meter is 
illustrated (Figure 56a, b). Venturoli did not identify 
the person who designed that meter, but Baumgarten 
made a special point of crediting Woltman. I t was, in 
fact, an improvement over the original Woltman 
meter (cf. Figures 50 and 56) , and Woltman probably 
had nothing to do with the changes that had been 
made. Tha t generous gesture, however, has resulted in 
numerous subsequent writers of modern hydraulic 
text books maintaining the same designation for this 
type of meter, i.e., Woltman meter, whenever they 
used Baumgarten's illustration. 
In any event, unless Venturoli himself conceived 
this improved model, the name of the person respon?
sible for it has not received the credit due him. By 
1847, this meter became a regularly manufactured 
product of the firm of Lerebours et Secretan of Paris. 
Copies of several of their catalogs illustrating it among 
their hydraulic instruments still exist. The Proprietors 
of Locks and Canals at Lowell, Massachusetts, pur?
chased from diem a meter of this type, which in 1956 
they contributed to the Smithsonian Institution 
(Figure 56c). 
This meter was just the first of two with which 
Baumgarten had become concerned. While using it, 
he realized that the relatively small pallets (or vanes) 
on this meter could utilize only a small portion of the 
total driving force present within the circle defined by 
their rotation; if the total force available within that 
NUMBER 28 57 
ttJ 
www o 
U b 
FIGURE 56.?Woltman current nreters: a, Venturoli's version, 1818; b, Baumgarten's drawing, 
1847; c, improved model manufactured by Lerebours et Secretan, Paris, (a, Redrawn by A. H. 
Frazier after Venturoli, Elementi di Mechanica e Hydraulica; b, from Baumgarten, "Sur le 
moulinet de Woltmann"; c, NMHT 314769, Smithsonian photo 73-777.) 
circle were made use of, the driving force would be 
much enhanced. In fact, a rotor of much smaller over?
all dimensions probably could be used without any sac?
rifice of power. He accordingly suggested that change 
to his supervisor, Jean Victor Poncelet (member of 
the French Academy of Sciences), who assigned a 
Paris instrument-maker named Conte to work with 
Baumgarten to produce a new meter with at least two 
rotors of the suggested type. Each rotor was to have 
four helicoidal blades surrounded by a wide metal 
band for strengthening the assembly. Each blade ex?
tended to the axle, and occupied one-fourth of the 
projected area within the ring. The rotors differed 
however, in that they had pitches of 0.08 and 0.12 
meters, respectively. Either could be installed on the 
same meter, so that their performances could be com?
pared under identical operating circumstances. The 
meter was completed late in 1846. During the months 
58 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 
FIGURE 57.?Baumgarten's current meter, manufactured by Secretan of Paris, ca. 1846. 
(NMHT 314773, Smithsonian photo 44536.) 
that followed, Baumgarten performed his tests on it 
while conducting his studies on the Garonne River. 
Illustrations of it appeared in Secretan's catalog (suc?
cessors to Lerebours et Secretan?Marc Lerebours 
having died in 1867) for numerous years. Baumgar?
ten died a suicide in 1859. 
Two of the 1846 models were to contribute to hy?
draulic history in America. The Proprietors of Locks 
and Canals of Lowell purchased one of them (Figure 
57), and Clemens Herschel, the noted hydraulic en?
gineer who often did work for those Proprietors, pur?
chased the other. 
In the early 1870s, two major hydraulic projects 
were being undertaken in the northeastern United 
States. General Theodore Grenville Ellis (1829-1883), 
a member of the Corps of Engineers. U.S. Army, un?
der the Chief of Engincrs, A. A. Humphreys, had 
been placed in charge of a study aimed at improving 
the Connecticut River for navigation, and Alphonse 
Fteley (1837-1903) had been named the resident en?
gineer in charge of the construction of the new water 
supply for Boston from the Sudbury River. Baumgar?
ten current meters served a useful purpose on both of 
those projects. 
In about 1870, when General Ellis began his work 
on the Connecticut, he purchased the Baumgarten 
current meter from Clemens Herschel. In view of 
General Humphrey's strong opposition to the use of 
such instruments, it seems likely that any publicity 
regarding its purchase would have been kept to a min?
imum. In fact, when Ellis wrote his official report on 
the project, and had to admit having made use of 
such a current meter, he spent several pages explain?
ing his reasons for having done so.80 His arguments 
were so convincing that Humphrey credited h im -with 
having used good judgment, and the f?an against the 
Army's use of current meters was thereupon lifted. 
Before Ellis could make any use of the Baumgarten 
current meter, it had to be rated to establish an equa?
tion showing the relationship between the number of 
feet per second (f), at which the water was flowing, 
and the number of revolutions per second ( n ) , per?
formed by the rotor. Ellis made one such rating in 
1870, and another in 1874, and found fhat for vel?
ocities between 0.7 and 9.0 feet per second that equa?
tion was: f = 5/12 n + 0.25. On the same occasions, 
however, he learned that the meter "ceased to register 
accurately and in exact conformity with the formula 
below 0.7 feet per second.'' 81 
Ellis made considerable use of this meter during the 
first four years of his work on the Connecticut River, 
but its lack of precision in the lower velocity range, 
caused him to explore other possibilities. By June 1874 
he had designed a vertical-axis cup-type current meter 
similar (but smaller) to that designed several years 
earlier by Daniel Farrand Henry of the U.S. LaTce 
Survey. The new "Ellis" meter was so superior to 
Baumgarten's model that he performed the remain?
ing measurements of his project with the new one. 
NUMBER 28 59 
FIGURE 58.?The principle hydraulic engineers who constructed the Sudbury River water-
supply system for Boston and designed many other outstanding hydraulic projects in America: 
a, Alphonse Fteley; b, Frederick Pike Stearns. 
The "Ellis" meter will be discussed shortly. The 
point to be observed here is that the Baumgarten 
meter played an important part in overcoming the 
Corps of Engineer's prejudice against the use of cur?
rent meters, and it contributed to the development of 
Ellis' considerably better instrument here in America. 
Work on the Boston water-supply project began in 
1873, just a short while before Ellis stopped using the 
Baumgarten meter. Alphonse Fteley (Figure 58a), 
who was the resident engineer in charge of the proj?
ect, soon found that he too needed a current meter. 
The need was met by borrowing the Baumgarten 
meter from Ellis, and having a local instrument manu?
facturer, Buff and Berger, make a copy of it (Figure 
63a). The new model differed from the original in 
two respects: its rotor was slightly larger in diameter, 
with more blades having a longer pitch; and the 
facility for disengaging the counting wheels was re?
versed in that the spring that formerly kept those 
wheels disengaged (until activated by a pull on the 
operating cord) now kept them engaged during the 
periods of operation. It had been noted while in Ellis' 
possession, that the force applied to the cord was 
sometimes great enough to damage the gears. Such 
an effect could not take place if the spring were used 
to keep those gears in mesh, and the cord used only 
for disengaging them. A drawing of that new current 
meter (Figure 63a) appeared in an article by Frede?
rick P. Stearns, Fteley's principal assistant (Figure 
58fc). 
Fteley and his assistants used this meter for several 
years for measuring the flow of the Sudbury River 
and nearby streams. He also found it satisfactory in 
most respects, except for measuring low velocities. 
Like General Ellis, he thereupon developed a new 
meter. 
About the only part of the new meter which re?
sembled any part of Baumgarten's was the rotor, and 
even that was modified. It had several more vanes, all 
with a longer pitch. The axle extended completely 
through die rotor, and was supported by both front 
and rear bearings. The counting wheels were smaller 
in diameter, and arranged to face upward, so that the 
operator could read them without lifting the meter 
completely out of the water. The first models of this 
meter were manufactured by Buff and Berger. 
60 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 
I t should be noted that the Fteley meter (often re?
ferred to as the "Fteley-Stearns Meter" because 
Stearns assisted in its development) was of a special-
purpose type. Its major purpose was to measure, 
through a manhole, the velocities occurring in under?
ground conduits which had been built for conducting 
water from the Sudbury River to Boston. It was 
always suspended from a rod. The operator could 
therefore easily maintain its proper orientation which 
eliminated the need for a tailpiece. While that feature 
admirably served the need on this water-supply proj?
ect, it restricted the use of the meter to relatively shal?
low streams and conduits where cable-suspension fac?
ilities (and tailpieces) were not essential. 
Practically no changes were made in the design of 
the Fteley-Stearns meters for over 25 years. In 1911, 
however, while still an Assistant Engineer of the Prop?
rietors of Locks and Canals at Lowell, Massachusetts, 
Arthur T. Safford (1867-1951) proposed changing 
the design of that meter by decreasing the number of 
vanes thereon from 8 to 6, increasing the diameter of 
the rotor from V/i to 5 inches, and making the frame 
larger and somewhat stronger. 
FIGURE 59.?A current meter contributed to the Smithsonian 
Institution by the Proprietors of Locks and Canals of Lowell, 
Massachusetts, which may be an experimental model de?
signed by A. T. Safford. (NMHT 314771, Smithsonian photo 
44536-C.) 
FIGURE 60.?Comparison of the original (a) and improved 
(b) Fteley-Stearns current meters as presented by Hughes 
and Safford, A Treatise on Hydraulics, 1916. 
FIGURE 61.?A Fteley-Stearns current meter manufactured 
by C. L. Berger & Sons, Boston. (NMHT 330410, Smith?
sonian photo 75409.) 
NUMBER 28 61 
Although its record is not entirely clear, there is in 
the Smithsonian collection, a current meter (Figure 
59) that came from the Proprietors of Locks and 
Canals, which has about the same type of rotor that 
Safford had advocated. Its counting gears, however, 
are located in a rather bulky metal box behind the 
rotor with a glass window at one side for observing 
the readings. Since no other current meters like it are 
known to exist, this might well have been an experi?
mental model which Safford had designed while de?
veloping the "improved" instrument. The final model 
was provided with a much smaller counting wheel 
box, which faced upward and was located in a far 
more convenient location. Figure 60 shows a com?
parison between the old Fteley-Stearns and the new 
Safford models. 
In later models, the counting wheels were elimin?
ated entirely in favor of the electrical contact method 
as conceived by Daniel Farrand Henry. While all this 
had been taking place, the firm that had constructed 
the original Fteley-Stearns meter, Buff and Berger, 
had dissolved its partnership, and both members 
thereof set up separate businesses, but both of those 
separate firms continued manufacturing all of the 
models in which Fteley, Stearns, and Safford were 
involved. One of those later models, as manufactured 
by C. L. Berger & Sons, was eventually added to the 
Smithsonian collection (Figure 61) . 
From all these events it is apparent that the Baum?
garten current meter that Clemens Herschel sold to 
General Ellis produced a truly notable impact on the 
design of such instruments in America. This, however, 
does not mark the end of the saga. The story of the 
meter shown in Figure 57?the one that the Propri?
etors of Locks and Canals purchased at the same time 
that Herschel obtained his?also deserves attention. 
James Francis, who at that time was the Chief En?
gineer of Locks and Canals of Lowell, Massachusetts, 
was favorably impressed with the Baumgarten current 
meter although he too recognized as a deficiency its 
failure to operate satisfactorily at low water velocities. 
In the belief that much of that deficiency could be 
remedied by improvements in the bearings, he re?
quested Herschel to take the matter up with George 
Louis Buff (1839-1923), the senior member of the 
Buff and Berger firm in Boston, to see what he 
thought could be accomplished in that respect. Buff 
was born in the university city of Geissen, Germany, 
FIGURE 62.?Three experimental rotors manufactured by Buff and Berger, Boston, ca. 1876, 
for trial on the new "Herschel" meter, an American version of the Baumgarten meter (NMHT 
314766, 314767, 314768; Smithsonian photo 44536-B.) 
62 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 
and was of the old German school of fine instrument 
makers. 
A transcription of the first letter, dated 20 Septem?
ber 1876, that Herschel wrote to Francis on this sub?
ject and which had been preserved in the Office of the 
Proprietors of Lock and Canals, follows: 
To James B. Francis 
Civil Engineer, 
Agt. Props. Locks & Canals 
Lowell, Massachusetts. 
From Office of Clemens Herschel 
Civil and Hydraulic Engineer, 
66 State Street, Boston, 
Sept. 20, 1876. 
Dear Sir: 
I have not exactly got Mr. Buff started on making your 
new current meter, but am gradually starting him. My idea 
is to make the instrument of certain defined dimensions & 
mathematical shapes or forms throughout, so that from its 
description, another just like it may be made elsewhere. If I 
can induce someone to order another instrument, we can 
then try whether two instruments made exactly alike (the 
word "exactly" being used in the common mechanic's sense 
of that term) will register velocities alike, or how near alike. 
Now, to the end of making the new instrument such that it 
can be regarded as a model, and, (if two instruments made 
alike, register alike) to the end that our experiments may be 
considered valid for many other like instruments, it has 
occurred to me that it might be advisable to make the new 
current meter in the metric dimensions. Of course, it can be 
rated to any desired measures & used in the same; the ar?
ticle itself only, to be bounded & described metrically. How 
does this idea strike you? Mr. Buff is neutral in the matter, 
and as for me, I have no decided wish either way; perhaps 
this is being neutral also. Will you please decide. 
When we get a sketch of the proposed instrument I will 
show it to you before starting on the construction of the 
instrument. The model for the propeller wheel is to be 
begun in July, but I will stop it until I hear from you. It is 
to be a true helicoid, cut into 4 equal parts, and placed 
around the axis so as to occupy the V* height of the whole 
helicoid, a mathematical figure that can be reproduced even 
should the model be lost. 
Truly yours, 
[signed] Clemens Herschel 
In a second letter, dated 22 September 1876, that 
Herschel wrote to Francis, he transmitted a list of 
ideas he had in mind for the new meter. 
General Plan for Current Meter 
1. The propeller wheel to be abt. 5" diam., each V4 part of 
a true helicoid of 5" rise. This makes the wheel VA" 
deep. A guard rim at periphery. The wheel to be set 
well forward of the rest of the instrument. 
2. The two journals to be agate- the collar & the end-pivot 
of German silver. 
3. The propeller wheel and the axis that turns with it} to 
4. 
be without weight in water; this to be attained by mak?
ing the axis hollow. 
The counter-wheels, throw-in & out gear, & general 
frame, like the one owned by Locks & Canals & the one 
once owned by C. Herschel, now by Genl. Ellis. 
5. The frame to be a closed box, however, the side next the 
figured side of the counter wheels of glass, and so ar?
ranged that it may be filled with water. 
6. The spindle large enough to hold a 2Vz inch rod. 
7. All the dimensions of the instrument to be some even 
measure, & the shapes mathematical shapes, so that the 
instrument can be reproduced from its description. 
(2 & 3, I should expect, will about anhilate [sic] the friction 
at the axis. 5 causes all the parts to move always in the 
same medium, whether working in clean or gritty water, 
etc.) 
Sept. 22, 1876 
FIGURE 63.?Current meters in the 1885 catalog of Buff and 
Berger, Boston, probably the first American firm to list such 
meters in its catalog: a, copy of Baumgarten meter request?
ed by Ellis for the Boston water-supply project; b, c meters 
made for Proprietors of Locks and Canals, Lowell, Massa?
chusetts; d, Ellis' cup type meter. 
NUMBER 28 63 
In connection with this development project, three 
different experimental rotors were built. Two of them 
had four helicoidal blades each, and one had five of 
them. One had just a plain metal band surrounding 
the blades, the other two had flat, hermetically sealed 
tubes in that location. Those tubes, being filled with 
air like the balls on the Revy current meters, caused 
the rotors to have the same weight as water, thereby 
reducing the pressure (and consequently the friction) 
on the bearings. The two rotors that had the 
"weightless" feature were six inches in diameter, 
whereas the one having just a plain band around it, 
was five inches in diameter. All three of these rotors 
have been preserved, and arc in the Smithsonian col?
lection (Figure 62). 
The final outcome of all the experiments and nego?
tiations was that two models were produced. Both had 
agate main bearings. One (Figure 63b) continued 
the original use of counting wheels (but they were 
inclosed within a glass-covered box filled with clean 
water to keep out grit and fibers) ; the other (Figure 
63c) used the electrical-contact system which elimin?
ated the counting gears. An article, entitled "Current 
Meter?from advance sheets of Buff and Berger*s en?
larged catalog of Improved Engineer's Instruments," 
appeared in the 25 April 1878 issue of Engineering 
News and stated in reference to these meters that 
careful experiments were made at Lowell, in the summer of 
1877 under the direction of James B. Francis, Engineer of 
"The Proprietors of Locks and Canals on Merrimac River" 
and warrant to say that velocities as low as 0.17 of a foot 
per second can be measured. 
To have reduced the minimum velocity at which the 
meter could operate dependably from 0.70 to 0.17 
feet per second was indeed an important accomplish?
ment. It is believed that Buff and Berger is the first 
American firm ever to have listed current meters in 
its catalogs. 
Other American Models 
Hall's Current Meters 
While the Baumgarten current meter was making 
hydrometric history in the northeastern corner of the 
United States, something of a similar nature (al?
though not as extensive) was occurring in the Far 
West. It began in 1877 and 1878 when the Saxton 
current meter (as modified by General Abbot) had 
been used by the Corps of Engineers while making a 
FIGURE 64.?William Hammond Hall, California's first 
State Engineer. (Courtesy of Mrs. Hosea Blair.) 
study of the currents in San Francisco Bay (see Fig?
ure 55) . During the latter of those two years, William 
Hammond Hall (1846-1934) became California's first 
State Engineer (Figure 64), during which time he is 
most remembered for his conception and creation 
of San Francisco's magnificent Golden Gate Park. 
When the State legislature established a new Depart?
ment of Engineering as of 29 March 1878, it stipul?
ated that its primary objective should be to ascertain 
why the Sacramento and San Joaquin rivers flooded 
so frequently. California thereupon became the first 
State in the Union to engage in organized stream-
gaging activities, preceding the federal government 
by all of ten years in that respect. 
As State Engineer, William Hammond Hall was 
immediately faced with the problem of obtaining 
equipment with which to measure the flow of those 
rivers. The solution thereto was ultimately published 
in a report /3 which stated in part: "Six current me?
ters were used by the Department. Two of these were 
the property of the Engineer Corps of the U.S. Army, 
and four others were closely patterned after these 
two." From the description of those meters which fol-
64 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 
lowed, there can be no doubt that the two Corps of 
Engineers' meters were of the same type (if not the 
identical instruments) as had been used in San Fran?
cisco Bay. With respect to the other four meters (un?
doubtedly built in California), the writer added: 
"The blades of the wheels should be heavier, and their 
upper and front edges should be made sufficiently con?
ical in outline to ward off floating leaves, twigs, 
etc." 84 
Later in his career, Hall was employed in the Irriga?
tion Survey of the U.S. Geological Survey. A few of 
his current meters were acquired by that Survey for 
use in its early stream-gaging program. Two of those 
meters?one intended to be used while suspended 
from a rod, the other while suspended from a cable? 
were preserved and in time transferred by the Geolog?
ical Survey to the Smithsonian Institution (Figure 
65) . 
The Haskell Current Meter 
Amost every hydrographer worth his salt, who had 
used a current meter designed by someone else, seems 
to have come up with a better design of his own. So 
it was with Eugene Elwin Haskell (1855-1933) (Fig?
ure 66) . He graduated from Cornell University in 
1879. His earliest job experiences were in Detroit as 
a recorder for the Survey of the Northern and North?
western Lakes (now more commonly referred to as 
the "U.S. Lake Survey"), and in charge of a party 
of engineers employed by the Mississippi River Com-
O 
FIGURE 65.?Hall's current meters designed ca. 1880: a, meter for use with rod suspension 
(NMHT 289639, Smithsonian photo 445537-F); b, meter for use with cable suspension (NMHT 
289640, Smithsonian photo 44537-G). 
NUMBER 28 65 
FIGURE 66.?Eugene Elwin Haskell, Dean, College of En?
gineering, Cornell University, 1906-1921. (Courtesy of Cor?
nell University.) 
mission, measuring the discharge of the Mississippi 
River at Point Pleasant, Missouri. 
During the period 1885 to 1893, Haskell was em?
ployed in the U.S. Coast and Geodetic Survey. One 
of his first assignments there was to plot, under Pro?
fessor Henry Mitchell's supervision, the direction and 
magnitudes of the currents in New York Harbor. It 
was while he was so employed that he invented his 
current meter. It differed from the cup-type meters 
then in vogue on the Mississippi River in that his 
was of the earlier horizontal-axis, screw-type design, 
and it included a direction-indicating facility. To 
quote Haskell's Reminiscences: 
Mr. E. S. Ritchie, inventor of the liquid compass, had solved 
the problem of reading a distant compass electrically; ac?
cordingly I joined forces with him and a direction current 
meter was the result. This was put in use in the Spring of 
1886 on the New York Harbor work.85 
Haskell later used this current meter in a study of 
the currents off the Florida coast and in the Gulf 
Stream. As of 12 June 1888, U.S. Patent No. 384362 
was awarded to him for it (Figure 67). For many 
years thereafter, the E. S. Ritchie firm in Brookline, 
Massachusetts, manufactured them. 
In the course of his eventful and eminent career, 
Haskell became a member of several important re-
FIGURE 67.?The Ritchie-Haskell direction-indicating current meter. 
(CouUesy of U.S. Geological Survey.) 
66 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 
gional, national, and international commissions deal?
ing with hydraulics. In 1906 he became Dean of the 
College of Engineering at his old alma mater, Cornell 
University, a position he held until his retirement in 
1921. 
U.S. Irrigation Survey Models 
On 2 October 1888, Congress passed a Sundry Civil 
Bill appropriating $100,000 for studies concerned with 
irrigating the lands west of the 100th meridian. The 
new agency was called die United States Irrigation 
Survey, and made a part of the Geological Survey in 
the Department of the Interior. One of its first objec?
tives was to establish a temporary camp of instruction 
on the Rio Grande at Embudo, New Mexico, for 
training a group of young engineers in the art of gag?
ing streams.86 
At the time that bill was passed, the Geological Sur?
vey did not have any current meters or other stream-
gaging equipment with which that group could gain 
the desired experience. John Wesley Powell, then Dir?
ector of the Survey, appealed to some of the other 
likely federal agencies for the loan of any such in?
struments that they might have to spare. While wait?
ing for those agencies to respond, the group made 
measurements with different types of floats fashioned 
from locally available materials, and also by running 
levels down the stream to determine its slope, and 
computing the discharge from existing formulas. 
Powell's appeal eventually met with one lone res?
ponse. The Navy Department shipped to the camp a 
36-inch-long, cable-suspended Ritchie-Haskell direc?
tion-indicating current meter, such as shown in Figure 
67. It, however, turned out to be far too large and 
much too cumbersome for use in the shallow waters 
which normally occur at Embudo during the winter 
seasons. This being the only current meter available 
up to this point, they immediately set about redesign?
ing it in a manner that would better serve their needs. 
One of the group was sent with the resulting plans to 
an instrument-maker in Denver, and within a short 
period of time a much smaller and more convenient 
model, similar to that shown in Figure 68 (but ar?
ranged for rod suspension), was produced and placed 
in service. 
During the years that followed, almost a dozen 
variations from the Irrigation Survey's (and William 
Hammond Hall's) models were tested. Four of them 
along with the direction-indicating meter, were added 
to E. S. Ritchie and Sons' line. Two of diose four 
models (Figures 68 and 69) are now in the Smithso?
nian collection. The one shown in Figure 69 was 
listed in the catalogs as "Current Meter 'B' complete 
with lead weight and extra wheel." The rotors or 
FIGURE 68.?A variation of the Haskell current meter as conceived in 1888-1889 by engineers 
of the U.S. Irrigation Survey. (NMHT 248697, Smithsonian photo 44537-B.) 
NUMBER 28 67 
FIGURE 69.?Current Meter B (an early variation of the Haskell current meter) with sounding 
weight, manufactured by E. S. Ritchie & Sons, Brookline, Massachusetts, ca. 1900. (NMHT 
316590, Smithsonian photo 72237.) 
"wheels" then in use had diameters ranging from Th 
inches down to 5!/2 inches. Some had a high (screw) 
pitch, others had a low pitch. The latter would oper?
ate better in the lower velocities, although they ceased 
to perform reliably below 0.5 foot per second. When 
operating in velocities above say four feet per second, 
they revolved so rapidly that their revolutions could 
not be counted accurately. The slower turning, higher 
pitched wheels would then be installed on the meters. 
In 1889, the activities of the Irrigation Survey were 
practically brought to an end, but in 1904, the Water 
Resources Branch of the Geological Survey was offici?
ally activated, and stream-gaging operations were re?
vived not only in the area west of the 100th meridian, 
but throughout the entire United States. This work is 
still being carried on. At present the more recently de?
signed, vertical-axis, Small Price current meter (on 
which only a single rotor is required) is the favored in?
strument of the Survey, but for several of its earliest 
years, meters of the type just described had been 
preferred. 
Other European Developments 
Moore's Current Meter 
While the foregoing events were taking place in 
the United States, European engineers were also tak?
ing considerable interest in the design of current me-
68 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 
FIGURE 70.?A current meter patented in 1875 in the United States by Benjamin T. Moore of 
Middlesex County, England (NMHT 308551, Smithsonian photo 44536-H.) 
ters. The Saxton and Revy meters manufactured by 
Elliott Bros, in London, and the Baumgarten meters 
manufactured by Lerebours and Secretan in Paris, 
have already been discussed, but no mention has yet 
been made of the Moore or Ott meters made respect?
ively in England and Germany. 
Benjamin T. Moore obtained a U.S. Patent (No. 
169024, dated 19 October 1875) for his "current me?
ters, water meters, and ships' logs." On 1 January 
1876, he used the current meter to measure the flow 
of the Thames River at Staines, about 20 miles up?
stream from London. (The discharge amounted to 
2612 cubic feet per second.) 
At the time this patent was granted to Moore, cur?
rent meters were all classified by the U.S. Patent Of?
fice under "Ships' Logs." 
The earliest American patents for current meters were taken 
out in 1851. There are now [1927] on file in the Patent 
Office, classified under ships' logs, more than 50 patents for 
devices for measuring the velocity of water. Many unpat?
ented devices have also been constructed.8' 
Moore not only described his instruments in his pat?
ent, but he also submitted to the Patent Office a 
model of his current meter. That model was later trans?
ferred to the Smithsonian Institution (Figure 70) . 
The Firm of A. Ott 
In 1790, Reinhard Woltman publicly introduced his 
horizontal-axis water current meter. Its basic design 
soon became traditional and many of the improved 
models which came after it were called "Woltman" 
meters, out of respect for the original inventor. A firm 
that perhaps has done the most to preserve this tradi?
tion is that of A. Ott of Kempten, Bavaria?today in 
West Germany. Albert Ott (1847-1895), its founder 
(Figure 71a), was the son of a farmer and postmaster 
in Nesselwang, South Bavaria. After serving an exact?
ing apprenticeship in the shop of his uncle, Clemens 
Riefler, who manufactured drawing instruments in 
Nesselwang, he attended the Polytechnic School in 
Munich. For short periods thereafter, he worked at 
instrument shops in Munich, Vienna, Berlin, London, 
and Milan before returning to Bavaria. 
In 1873, A Ott and G. Coradi became partners in 
a small shop in Kempten, where they manufactured 
surveying instruments. Seven years later, however, Co?
radi left for Zurich to establish a separate, and sub?
sequently famous, shop of his own. 
NUMBER 28 69 
FIGURE 71.?The Ott family of instrument manufacturers: a, Albert Ott, 
founder of the firm of A. Ot t ; b, Herman Ot t ; c, Ludwig A. Ott. 
Upon being left the sole owner of the shop in 
Kempten, Ott sought ways of increasing his line of 
scientific instruments. In 1881, therefore, when a lead?
ing hydraulic engineer, Professor Andreas Rudolph 
Harlacher, head of the Hydrographic Services 
in Bohemia, proposed to Ott that he manufacture 
Woltman current meters supplied with electric regis?
tering facilities on which Harlacher possessed a pat?
ent, Ott complied eagerly. Ever since then, the Ott 
firm has supplied Germany and many other countries 
throughout the world with current meters, practically 
all of which have been of a horizontal-axis type such 
as Woltman had originally conceived. 
This was a family-owned firm, and when Albert 
died, it was inherited by his two sons, Herman (Figure 
716) and Ludwig (Figure 71c) with Ludwig (when 
coming of age) taking the most active part in its oper?
ations. In the course of time, Ludwig received a Doc?
tor of Engineering degree from the Technical 
University in Munich, and was honored for the ex?
cellence of his hydrometric, cartographic, and mathe-
matic instruments. Among the several instruments 
manufactured by the Ott firm that have been con?
tributed to the Smithsonian Institution are the two 
fairly recent current meters shown in Figure 72. 
After Ludwig Ott's death in 1946, his elder brother, 
Herman, carried on the administrative and develop?
mental work. 
Steponas Kolupaila 
During the course of its highly successful operations, 
members of the Ott firm collaborated with many dis?
tinguished European hydraulic engineers and often 
incorporated their suggestions into their instruments. 
The circumstances under which one such engineer, 
Dr. Steponas Kolupaila (1892-1964) became involved 
warrants special attention here. 
Before World War I I , Kolupaila had been in charge 
of Lithuania's Hydrometric Bureau, an agency which 
was comparable to that of the Water Resources Divi?
sion of the U.S. Geological Survey. Data concerning 
the discharge of rivers in Lithuania were collected 
and published under his supervision, as was the rating 
and repair of the current meters used on such work. 
In fact, the meters used in neighboring countries like 
Estonia and Latvia were often sent to him to be rated. 
In 1940, Estonia, Latvia, and Lithuania were over?
run by the Russian army, and their freedoms as inde?
pendent republics came to an end. Dr. Kolupaila was 
among the few scientifically trained engineers who 
70 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 
n?^ ? 
a 
FIGURE 72.?Ott current meters: a, ca. 1917 (NMHT316593, Smithsonian photo 72242); 
b, ca. 1932 (NMHT 316595, Smithsonian photo 72256). 
fled to Germany, where he found employment in the 
firm of A. Ott. One of his projects during the four 
years while he was there was to develop a rotor for 
use on horizontal-axis meters that would register only 
that component of the velocity of a stream which cor?
responded with the direction in which the meter was 
pointing. In other words, if a meter held on a rod, 
were pointed directly into the current, the rotor would 
register 100 percent of the velocity in effect there, 
whereas if it were pointed at right angles from that 
direction, the rotor would not turn at all. At any 
intermediate angle, the rotor would revolve at a rate 
which represented the corresponding component of 
the velocity. This innovation is of particular import?
ance where a meter can be held in a fixed position 
and used in highly turbulent water, or in places where 
water tends to flow at unpredictable angles such as 
occurs in the vicinity of hydraulic turbines. 
Kolupaila succeeded in developing such a rotor. Be?
fore leaving that firm in about 1944 to accept a posi?
tion in America as Professor of Civil Engineering at 
the University of Notre Dame, the Ott firm presented 
him with one each of the major instruments on which 
he had contributed improvements. The instrument 
case containing a current meter with his "component" 
rotor, carries a brass plate engraved as follows: 
TO OUR HYDROMETRICAL COLLABORATOR 
PROFESSOR STEPONAS KOLUPAILA 
IN GRATITUDE FOR VALUABLE SCIENTIFIC WORK 
A. OTT, MATH. MECH. INSTITUTE 
KEMPTEN, BAVARIA 
After Kolupaila's death in 1964, that case of cur?
rent meters, which included numerous accessories, was 
presented to the Smithsonian Institution (Figure 73). 
His "component rotor" appears in Figure 74. 
NUMBER 28 71 
P pi 
? 
FIGURE 73.?Current meters and accessories presented to Dr. Steponas Kolupaila for designing 
the "component rotor." (NMHT 328631, Smithsonian photo 62664.) 
FIGURE 74.?A modern Ott meter equipped with Kolupaila's 
"component rotor." (NMHT 328631, photo by A. H. Fra?
zier. ) 
72 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 
VERTICAL-AXIS METERS 
During the development of instruments for stream 
gaging, a number of current meters were produced, 
which, although never generally accepted, are never?
theless of considerable historical interest. Such was the 
case with the Hooke and Focacci meters, previously 
discussed, and such was the case with the little-known 
Tolotti meter. 
Most of the presently available information con?
cerning the Tolotti meter is contained in a little 
pamphlet entitled Rota Indrometra, by Antonio Sem-
piterni Tolotti. The drawings in that pamphlet were 
obviously prepared by an unskilled draftsman, so a 
more readily understood modern perspective drawing 
thereof is being presented in Figure 75. The apparatus 
consisted of a circular rotor with seven equally spaced, 
V-shaped vanes around its periphery, all mounted 
within a box-like container. The downstream face of 
that container was left completely open, but a half of 
its upstream face was closed to form a shield for the 
vanes moving in the upstream direction (a practice 
followed in several modern instruments). Its axle was 
supported on an upward-pointing pivot (also a mod?
ern practice). The axle projected well above the sur?
face of the water, where a pointer was attached to it, 
which enabled the operator to count and time its 
revolutions. Although this apparatus badly lacked 
streamlining, the principle of its operation is essenti?
ally the same as that of many modern current meters. 
The Tolotti current meter in turn had forerunners 
FIGURE 75.?Tolotti's "rota idrometrica," ca. 1823, a fore?
runner of modern vertical-axis current meters. (Drawn by 
A. H. Frazier, from Tolotti, Rota Idrometrica.) 
FIGURE 76.?Cross-section of early Persian windmill, a fore?
runner of the Tolotti current meter. (Drawn by A. H. Fra?
zier after Vowles, "Early Evolution of Power Engineering," 
plate 24.) 
NUMBER 28 73 
of its own but in the meteorological field. For exam?
ple, in an article entitled "Early Evolution of Power 
Engineering" by Hugh P. Vowles is a "diagrametric 
cross-section of a Persian windmill," a copy of which 
appears in Figure 76. The windmill too, operated on 
the same principle, and Vowles implied in his ar?
ticle that such windmills may have been used in Persia 
as early as the 7th century A.D. 
FIGURE 77.?Daniel Farrand Henry. Note parts of a current 
meter and counting mechanism on table; cf. Figure 78. 
(Painting by Percy Ives, courtesy of Prismatic Club, Detroit, 
Michigan.) 
The Henry Meter 
The current meter that initiated the present vogue 
of current meters of the vertical-axis type was the one 
designed by Daniel Farrand Henry (1833-1907) of 
the U.S. Lake Survey in 1868 (Figure 77). A replica 
of the meter is now in the Smithsonian collection 
(Figure 78). 
Not long after the Civil War, Henry (no relation 
of Joseph Henry, the first Secretary of the Smithso?
nian Institution) had received orders from his super?
visor, General William Franklin Raynolds, to measure 
the discharge from several of the Great Lakes. During 
the course of that project, he built a current meter 
like that shown by installing a flier (rotor) from one 
of his Robinson cup-type anemometers into a suitable 
frame and fitting it with an electric contact facility 
for counting its revolutions (the first successful device 
of that nature) . He rated the assembly in the still 
waters of a convenient reservoir. The complete story 
regarding this historic meter appears in the Fall 1964 
issue of Technology and Culture.66 
Despite the fact that both Henry and his supervisor 
were severely disciplined by the Chief of Engineers, 
General A. A. Humphreys, for not having followed 
the "double float" method prescribed in the famous 
Humphreys and Abbot report on the Mississippi Riv-
FIGURE 78.?Replica of Henry's cup-type, electric-contact current meter. 
(NMHT 317670, Smithsonian photo 72258.) 
74 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 
er, this meter started the vogue favoring vertical-axis 
cup-type current meters, which persists throughout 
North America to this very day. 
When, in 1876, the United States International Ex?
hibition was held in Philadelphia for commemorating 
the Nation's first centennial, Henry was persuaded to 
exhibit his current meter and an inlet pipe strainer 
for water works as a part of the display of the Amer?
ican Society of Civil Engineers (an organization of 
which he was a member) . Because of the electrical 
counting facility he had installed on that meter, it 
became classified among the "electric" rather than 
the "hydraulic" instruments at the exhibit. Joseph 
Henry of the Smithsonian Institution judged those in?
struments, and it was he, therefore, who wrote the 
following Judge's report awarding Henry a medal for 
his exhibits: 
AWARD 351: D. FARRAND HENRY, DETROIT, MICH?
IGAN, U.S.A. CURRENT METER AND INLET PIPE 
' AND STRAINER FOR WATER WORKS 
Report 
Commended for an improvement on the ordinary form of 
current meters and for the application of electricity to the 
recording part of the instrument; also for the arrangement 
of a strainer and inlet pipe for water works, so as to prevent 
the interruption from the accumulation of anchor ice. 
The Ellis Meters 
The man who had pursuadcd D. F. Henry to ex?
hibit his current meter at the Philadelphia exhibition, 
was General Theodore Grenville Ellis (1829-1883) 
(Figure 79), a vice-president of the American Society 
of Civil Engineers, and the Chairman of its Centen?
nial Commission. During the Civil War, he had par?
ticipated in the Battle of Antietam and no less than 
23 other engagements while pursuing General Lee to 
Appomattox. After the war he returned to Hartford, 
Connecticut, where he had made his home since 1854, 
and resumed his engineering activities. In 1867 he was 
placed in charge of the U.S. Corps of Engineers' navi?
gation-improvement study of the Connecticut River, 
a job on which he remained for about ten years. 
While measuring the flow of the Connecticut dur?
ing his earlier years on that job, he initially followed 
the procedure recommended in the Humphreys and 
Abbot report, namely that of using the double-float 
method. Like Daniel Farrand Henry in the Great 
Lakes area, however, he ultimately decided to give 
FIGURE 79.?General Theodore G. Ellis. 
(Courtesy of Library of Congress.) 
current meters a trial. One of his first steps in that 
direction was, as previously stated, to acquire the 
Baumgarten meter which Clemens Herschel had pur?
chased from the Secretan firm in Paris (Figure 57) . 
In the meantime, Henry, with the consent of his 
supervisor, General Raynolds, had been using his cup-
type current meter with gratifying success. Reports 
thereon were being printed in the same House and 
Senate Executive Documents in which the reports of 
Ellis' own work on the Connecticut River were being 
published, so he became fully aware of them as well 
as aware of the criticism which the Chief of Engineers 
Humphreys was heaping upon those two hapless Lake 
Survey engineers. Despite that criticism, Ellis pro?
ceeded in 1874 to build a current meter very similar 
to, but much smaller than, Henry's. His official report 
thereon, supported by his own immediate superior, 
General G. K. Warren, was expressed in such diplo?
matic language that Humphreys even praised his ac?
tion. By the time the Ellis' report of 20 March 1875 
NUMBER 28 75 
was being prepared, the controversy in the Corps of 
Engineers about the use of current meters had sub?
dued to such an extent that Ellis ventured to add the 
following footnote to his description of the new cur?
rent meter: 
A telegraphic current-meter was first used by D. Farrand 
Henry, esq., civil engineer, upon the United States lake sur?
vey, and to whom the writer is much indebted for valuable 
suggestions in the use of the instrument. A full description of 
Mr. Henry's meter will be found in the Journal of the Frank?
lin Institute, volume LXI.00 
Figure 80 shows the two earliest versions of his 
meter, both of which are in the Smithsonian collection. 
They differ from each other in that the more recent 
model (Figure 806) is provided with a "contact 
chamber" which houses both the upper bearing of the 
rotor as well as the electric contact facility. In the 
earlier model (Figure 80a), the contacts took place 
in the open water, the method diat had been used on 
the Henry meters. It may be noted that the original 
model corresponds exactly with the illustration in Buff 
and Berger's 1885 catalog, as previously shown in Fig?
ure 63. 
The use of Ellis meters spread quite rapidly after 
he had rated his first model in June 1874, particularly 
among the hydrographers of the Corps of Engineers 
(then the largest group of current meter users in die 
United States). With the introduction of the meter 
designed by W. G. Price in 1882, however, its popular?
ity soon came to an end (page 78). 
The Nettleton Meter 
Edwin S. Nettleton (1831-1901) (Figure 81), was 
born in Medina, Ohio, and educated at the Medina 
Academy and Oberlin College, after which he became 
an apprentice of Zacharia Deane in civil and mechan?
ical engineering. He reached the age of maturity when 
Horace Greeley's admonition, "Go West, young man, 
FIGURE 80.?Early Ellis current meters: a, as originally designed (NMHT 317669, Smithso?
nian photo 72257) i b, with first improvement (NMHT 289637, Smithsonian photo 44538). 
76 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 
^ M IjfeMtJ ^^^1 
FIGURE 81.?Edwin S. Nettleton and his current meter. 
(Portrait from Eleventh Biennial Report of the State En?
gineer to the Governor of Colorado for the Years 1901 & 
1902; meter NMHT 289641, Smithsonian photo 44537-H.) 
and grow up with the country," began to have its 
greatest effect.91 
Apparently inspired by Greeley's oratory, Nettleton 
joined the Union Colony emigrating to Colorado in 
1870 as its engincer-in-chief. Upon their arrival in 
that State, he laid out the town and surroundings of 
Greeley, and built its irrigation canals. In 1871 he 
laid out the towns of Colorado Springs and Manitou, 
complete with a canal system for that area. 
By 1881 the legislature of Colorado had appointed 
its first State Engineer, one Eugene K. Stimson, who 
served in that capacity for the fiscal years of 1881 and 
1882. He was followed by Edwin S. Nettleton, who 
NUMBER 28 77 
carried that work forward for the next four years. It 
is of interest in this connection that during most of 
those years his Assistant was Ellwood Mead, for 
whom Lake Mead, the lake impounded by the well-
known Hoover Dam between Arizona and Nevada, 
has been named. 
Of greater interest, insofar as the present study is 
concerned, is the current meter that Nettleton de?
signed. In his account of the stream-gaging operations 
published in the Biennual Report to the Governor of 
Colorado for 1883-1884, he remarked: 
At first the Fteley current meter was used for measuring cur?
rent velocity, but it was soon apparent that this instrument 
was entirely too delicate for the rough torrents, filled with 
drift of all sorts, in which it was necessary to use it. An in?
strument was designed by me more suitable to the work 
(named the "Colorado" current meter), a description of 
which is given elsewhere. The main object kept in view in 
designing this instrument, was to make it self-clearing, the 
great defect of the Fteley meter being its liability to error 
from clogging with grass, weeds, etc. which at times would 
vitiate many hours' work Three "Colorado" meters 
having been made for this department by W. E. Scott & Co. 
of Denver; these instruments have since been in continuous 
FIGURE 82.?The "Bailey" meter, a modified version of Nettleton's meter, ca. 1889. 
(NMHT 24896, Smithsonian photo 44538-A.) 
78 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 
use in gauging rivers and ditches giving entire satisfaction. 
I Italics added.] 
One of the current meters built for him by W. E. 
Scott & Co. is shown in Figure 81. I t will be seen that 
the major change from the Fteley-Stearns current 
meter (Figure 61) consisted of substituting a vertical-
axis rotor, such as General Ellis had used on his me?
ters, for the horizontal-axis, screw-type rotor that 
Fteley preferred. 
In 1889, after the U.S. Geological Survey's "Camp 
of Instruction" for the Irrigation Survey got under 
way at Embudo, New Mexico, Nettleton, like Califor?
nia's State Engineer William Hammond Hall, lent a 
model of his current meter to that Survey. Soon the 
engineers at that camp redesigned Nettleton's meter, 
just as they had redesigned the Navy Department's 
Haskell meter, only this time the change was not as 
drastic. I t consisted merely of enclosing the counting 
wheels within a glass-covered compartment so as to 
keep silt and the plant fibers from interfering with the 
action of the gears. The revised instrument became 
known as the "Bailey" meter (Figure 82) , presumably 
because most of the change had been accomplished by 
the junior member of the firm in Denver then known 
as "Lallie and Bailey." As in the case of the Nettleton 
meter discussed above, one of these original "Bailey" 
meters, after having been preserved for many years by 
the Geological Survey, was transferred to the Smithso?
nian Institution. 
The Price Meters 
All of the remaining current meters presently in the 
Smithsonian collection are vertical-axis, "Price-type" 
models having cup-type rotors. As in the case of the 
previously described Woltman meters, numerous mod?
ifications have been made from the original model 
built by Price, but his name has always remained at?
tached to all of them even though some have failed to 
meet his approval. Meters of this type are by far the 
most commonly used in North America, whereas those 
of the horizontal-axis type are the most popular in 
Europe. 
William Gunn Price (1853-1928) (Figure 83) was 
born in Knoxville, Pennsylvania, but spent most of 
his youth in Chaseville, New York, about two miles 
southwest of the picturesque village of Schenevus. His 
aptitude for invention and engineering became evid?
ent quite early, and after having received four years 
FIGURE 83.?William Gunn Price. 
(Courtesy of W. G. Price, Jr.) 
of instruction in mathematics and engineering under 
J. H. Serviss at Engle wood, New Jersey, he embarked 
on a brilliant career in both of those fields.93 
Between 1879 and 1896 Price was an assistant En?
gineer with the Mississippi River Commission, meas?
uring the flows of the Mississippi, Ohio, and Missouri 
rivers, including many of their tributaries. In 1882, 
after having installed a river gage on the Ohio River 
at Paducah, Kentucky (Figure 84) , he conceived the 
design of his first current meter. The circumstances 
which prevailed on that occasion are described in the 
following letter which he wrote on 20 April 1927 to 
Nathan C. Grover, then Chief Hydraulic Engineer of 
the United States Geological Survey: 
In January, 1882, I began measuring the discharge of the 
Ohio at Paducah, Kentucky, under orders of Captain Smith 
S. Leach, Corps of Engineers, U.S.A., who was Secretary of 
the Mississippi River Commission. My equipment included a 
meter which was designed by Clemens Herschel. 
The Herschel meter was of the propeller type, having a 
horizontal shaft, and there were no means for excluding 
water from its bearings. 
NUMBER 28 79 
FIGURE 84.?The catamaran used by W. G. Price in 1882 for measuring the flow of the Ohio 
River at Paducah, Kentucky. Note current meter next to Price, second from right at stern of 
boat. (Courtesy of W. G. Price, Jr.) 
The Ellis meter had a cupped wheel which revolved in a 
horizontal plane, and there was no provision for excluding 
water from its vertical-shaft bearings. 
I rated these meters in clear, still water, and plotted 
ratings indicated that they would give accurate measure?
ments. 
I then began using them for river measurements. The 
water was very muddy, and boils in the swift current carried 
fine sand to the surface which I caught in my drinking cup. 
Neither would give discharge measurements which corres?
ponded with the gradual increase in gage. 
I then rated both meters in a bayou which had been 
recently filled with muddy water from the river, and the 
rating dots were irregular in location. Some dots indicated 
an increase of friction in the wheel bearings. 
I then rated the meters in a smooth-flowing chute, car?
rying sand and fine silt from the river. The meters were 
moved alternatively upstream and downstream. These ratings 
were very innaccurate, indicating the effect of grit in the 
bearings. 
I then wrote to Captain Leach that using these waters, I 
was unable to secure discharge measurements which at all 
corresponded with the daily increase in stage. The river was 
having a slow continuous rise. I asked Captain Leach to 
send me a meter which would give accurate measurements. 
The next day at 5 p.m. I received the following telegram: 
"Have no meter to send you. Do the best you can." 
Almost immediately the idea occurred to me that by using 
inverted cup bearings which would trap air, I could exclude 
the water and grit. I made drawings for such a meter that 
night, and by employing four mechanics, the meter was com?
pleted the next day at 3 p.m. 
This meter was used for measuring the great flood of that 
year, 1882.91 
In other documents, Price explained that among 
those mechanics he had employed to build the meter 
was a tinsmith, a blacksmith, and a locksmith. They 
were the best mechanics in town. The actual current 
meter constructed on that occasion is now one of the 
most treasured current meters in the Smithsonian col?
lection (Figure 85). 
Among the many U.S. patents that have been 
awarded to Price, the following four were for current 
meters: No. 325,011 dated 25 August 1885; No. 
80 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 
FIGURE 85.?The original Price current meter, built by him and four mechanics at Paducah 
Kentucky, in 1882. (NMHT 289638, Smithsonian photo 44538-H.) 
O I lull H FH IJ" 'I r" i ifi ~r 
FIGURE 86.?Price's current meters, ca. 1886, manufactured by W. & L. E. Gurley: a, 34-inch-
long %'ersion (NMHT 311708, Smithsonian photo 44538-D); b, 24-inch-long version' (NMHT 
289642, Smithsonian photo 44538-G). 
NUMBER 28 81 
FIGURE 87.?W. G. Price's subsurface direction meter with cover in place ca. 1886. 
(NMHT 316592, Smithsonian photo 72239.) 
582,874 dated 18 May 1897; No. 1,413,355 dated 18 
April 1922; and No. 1,571,433 dated 2 February 1926. 
On 14 January 1885, just before Price applied for 
the first of those patents, he wrote to the W. & L. E. 
Gurley firm of Troy, New York, saying in part: 
It is a great trouble to me to find a machinist who can make 
them, and I have been obliged to do all of the fine work 
myself. I wish you would undertake the manufacture of these 
instruments and furnish them to the U.S. Government at a 
reasonable price. . . . Of course, there is not much demand 
for them just now, as engineers are only just finding out that 
it is the only accurate way to measure the discharge of riv?
ers. But the engineers on the Mississippi alone are likely to 
require as many as 3 or 4 every year . . . .95 
Before the end of that year (1885), Price entered into 
a contract with the Gurley firm to manufacture his 
current meters on a royalty basis, and took a model of 
his 32-inch-long meter to them as a sample. While in 
Troy, a decision was reached for Gurley to manufac?
ture not only one, but two different models. The lar?
ger thereof (34 inches long, with a 7'/2-inch-diameter 
rotor) was announced in the 26th edition of Gurley's 
Manual of the Principle Instruments Used in Amer?
ican Engineering and Surveying (January, 1886) as 
their Item No. 375, "Deep Water and Harbor Meter," 
and the smaller (24 inches long with a 6-inch-diam-
eter rotor) as their Item No. 376, "River and Smaller 
Stream Meter." At the same time they introduced a 
Subsurface direction meter of Price's design which 
registered the compass direction of the velocity in the 
location at which it was positioned in the water. 
Models of these three instruments are shown in 
Figures 86 to 88. The 34-inch-long model (Figure 
86a) had originally been purchased from Gurley's by 
the Mississippi River Commission in about 1890. I t 
was used until 1929 by their engineers for measuring 
the flow of the Mississippi at various points between 
Rosedale and Vicksburg, Mississippi, and finally trans-
FIGURE 88.?Price's subsurface direction meter assembly with 
compass cover removed. When observations are made, an 
electrical current operates a solonoid within the sphere, 
which locks the position of the compass both vertically and 
horizontally until a reading is taken. (Courtesy of W. & 
L. E. Gurley.) 
82 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 
ferred to the Smithsonian in 1939. The shorter model 
(Figure 866) had been owned and used for many 
years by the U.S. Geological Survey before being 
transferred to the Smithsonian in 1916. 
Price was probably the Nation's foremost authority 
on current meters for a longer period than anyone 
else either before or after his time. Beginning in 1883, 
just one year after he had invented his first model? 
and continuing for ten years thereafter?he was in 
charge of the discharge-measuring operations of the 
Mississippi River Commission. He conducted many 
hydraulic studies such as those concerned with the 
shape of the vertical-velocity curves in rivers, and 
with the relationship between the velocity of the water 
at mid-depth as compared with the average velocity 
in the entire vertical at the same location. His active 
interest in such subjects continued until the very last 
days of his life. 
On one occasion in 1894, while working on the 
Missouri River for the Mississippi River Commission, 
he delivered a speech on irrigation at a conference at 
O'Niell, Nebraska. Newspaper accounts of that con?
ference described him as an "enthusiastic irrigation-
ist." In response to a need he found in that field, he de?
signed and patented his "Acoustic Current Meter" 
(Figure 89) . Tha t meter received its earliest publicity 
in an article entitled "A New Current Meter, and a 
New Method of Rating Current Meters" in the 10 
January 1895 issue of Engineering News. I t too, was 
manufactured by W. & L. E. Gurley. 
The rotor on this meter is smaller (only 5 inches 
in diameter) and lighter than that on any previous 
model. The word "acoustic" was used to identify it 
because of the manner in which sound was conducted 
from the instrument up to the ear of the operator. 
While the rotor would be making ten revolutions in 
the water, a worm gear on the upper end of its axle 
(which extended to the top of the enlarged chamber 
on the rod) would cause a lever (in the form of a 
tiny hammer) to be depressed against a spring. Upon 
completion of each tenth revolution, the hammer 
would be released, causing it to swing upwards and 
strike a metal diaphragm located in the upper end of 
the chamber. This cycle of operations would then be 
repeated over and over again as long as the rotor con?
tinued to turn. The sound produced each time the 
FIGURE 89.?Price's "acoustic current meter," ca. 1895, without brass suspension rods. 
(NMHT 316594, Smithsonian photo 72243.) 
NUMBER 28 83 
hammer struck the diaphragm would proceed up the 
inside of the hollow suspension rods to the earpiece 
worn by the operator, thus enabling him to count, by 
tens, and to time a certain number of the revolutions 
with a stopwatch. With the information thus obtained, 
he could enter a table of corresponding velocity values, 
and convert it into a figure representing the velocity 
of the water at the point of observation. These acous?
tic current meters were quite popular in North Amer?
ica for many years after their introduction. 
The last two current-meter patents awarded to 
Price were never manufactured. They both reflected 
an opposition he felt toward some of the changes that 
were being made from his earlier designs, and he had 
hoped to correct them. About two years after having 
received his final patent, he left on a trip from his 
home in Yakima, Washington, to Troy, New York, 
to confer with members of the W. & L. E. Gurley 
firm about manufacturing new meters which would 
contain those latest improvements; but that plan was 
never consummated. He got only as far east as Detroit, 
Michigan, when he was seized with a heart attack 
and taken off the train. Fie died soon thereafter in 
Detroit's Fort Shelby Hotel on 6 July 1928, his 75th 
birthday. 
The Geological Survey in the U.S. Department of 
the Interior became particularly concerned with cur?
rent meters and stream-gaging methods on two sepa?
rate occasions. The first was for a short period from 
1888 to 1890 when, as previously noted, the U.S. 
Irrigation Survey became a part of its activities. The 
second had its beginning in 1894, when Congress 
started appropriating funds for what is now known 
as the Water Resources Division of the Geological 
Survey. 
Before 1895, horizontal-axis current meters, such 
as those of the Haskell type which had been modified 
by engineers of the Irrigation Survey (Figures 68 and 
69), had enjoyed the greatest popularity. In March 
of that year, however, the University of Nebraska, 
which owned one of the smaller-sized Price current 
meters (Gurley's model No. 376 [Figure 866] ) , lent 
it to Professor O. V. P. Stout, a per diem employee of 
the Geological Survey, for making a streamflow meas?
urement. His report to the Survey about its perform?
ance was so enthusiastic, that within two months, the 
Geological Survey acquired one of its own. Tha t 
occasion marked the beginning of the Survey's prefer?
ence for meters of the Price type, a preference that is 
still in vogue. The Geological Survey has perhaps 
owned more current meters than any other organiza?
tion in the world. Well over 95 percent of them have 
been of the Price type. 
The early hydrographers in the Water Resources 
Division of the Geological Survey soon found it neces?
sary to accommodate themselves to a great variety 
of measuring conditions while gathering its streamflow 
data. Streams ranging in discharge from a mere trickle 
to the flow of the mighty Mississippi fell under their 
purview. Measurements varied in character from 
those made while wading the smaller streams to those 
made from bridges, cableways, boats, and even from 
ice cover. The instrumentation problems connected 
therewith were invariably the subject of many discus?
sions at the annual conferences of the Survey's district 
engineers. Prior to the conference held in Washington, 
D . C , in 1896, the Chief of the Division, Frederick 
Haynes Newell (1862-1932), requested that those en?
gineers come prepared to submit suggestions for im?
proving the current meters then in use. Edwin Geary 
Paul (Figure 90a,b), the mechanician of the Division, 
was instructed to incorporate the most practical 
thereof in the design of a new meter. His design, and 
its construction by W. & L. E. Gurley was completed 
on 12 November 1896 (Figure 90c) ; Paul, assisted by 
C. C. Babb of the Survey, rated it on 10 December 
of the same year at the rating station at Chevy Chase 
Lake, Maryland. This 12-inch-long meter, presently 
in the Smithsonian's collection made use of the same 
5-inch-diameter rotor that had been used on the Price 
acoustic meters. Its other parts were quite similar to, 
but considerably lighter than those on the large 
earlier models, which Gurley had been manufacturing. 
Because of its unusual method of suspension, there 
was no necessity for providing a horizontal vane on 
its tailpiece. It did, however, retain the electric con?
tact facility which characterized all cup-type current 
meters (other than the Price acoustic models) since 
the time of Daniel Farand Henry. 
This experimental model is the first Small Price 
current meter to have been built. Its lightness, and the 
ability to disassemble and pack it in a very small space 
appealed to many of the field hydrographers who 
often had to carry them and several other items of 
equipment for long distances on foot. It had been 
designed for cable suspension only, however, a cir?
cumstance that made it necessary for the field men 
to be supplied with a second meter that was capable 
of being suspended on a rod. Consequently, the design 
was soon modified to provide for both rod and cable 
84 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 
FIGURE 90.?Edwin Geary Paul and his Small Price current meter, 1896: a, E. G. Paul, ca. 1900; 
b, Paul, seated behind the U.S.G.S. rating car at Chevy Chase Lake, Maryland, ca. 1896; c, or?
iginal experimental model, built by W. & L. E. Gurley, Troy? New York, (a, Courtesy of Mrs. 
E. G. Paul; b, from U.S.G.S. Water-Supply and Irrigation Paper, 56, plate 12A; c, NMHT 
289643, Smithsonian photo 44538-E.) 
suspension. The resulting model appears in Figure 
91. (The accessory called a "double-end hanger," 
which could be installed between the tailpiece and 
the yoke for accommodating a suspension rod, is not 
shown in the photograph.) This model met with gen?
eral approval among the Geological Survey's field 
engineers, and the Gurley firm began manufacturing 
them as a stock item. That firm continued to be the 
primary manufacturer of such meters until several 
years after the Price patents had expired. 
Because of the many river-gaging stations that the 
Geological Survey established, its needs for current 
meters inevitably kept increasing. A point was finally 
reached where, to assure a continuing supply of repair 
parts, it needed to write its own specifications for 
these instruments. At about the same time, the Survey 
developed a policy of designing each new innovation 
in such a way that it could be incorporated in all of 
their earlier meters by merely replacing an old part 
with the appropriate modern one, thus up-dating the 
old models, and saving the expense of purchasing 
entirely new replacement meters. 
The two remaining current meters in the Smithso?
nian collection, (Figures 92 and 93) reflect that pol-
NUMBER 28 85 
icy. By about 1908, the meter's yoke was changed to 
provide a slot through which a thin, flat "hanger5 ' 
could be passed for suspending the meter and to take 
the place of the bulky "hanger" shown below the on the model shown in Figure 93, although the most 
meter in Figure 91. The new hangers were less ex?
pensive, less bulky, and far more streamlined than 
those earlier models. The improved yoke can be seen 
FIGURE 91.?One of the earliest Small Price current meters to be commercially manufactured, 
ca. 1897, by W. & L. E. Gurley. (NMHT 289644, Smithsonian photo 44538-F.) 
FIGURE 92.?An experimental Small Price current meter, ca. 1908; the first to be furnished 
with a "penta" contact chamber. (NMHT 289645, Smithsonian photo 44538-B.) 
86 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 
FIGURE 93.?A commercial Small Price current meter with Covert yoke and with one of its 
two interchangeable contact chambers, ca. 1912. (NMHT 323836, Smithsonian photo 44537-D.) 
important feature of that particular meter is the new 
"penta count" contact chamber on it. On all earlier 
models of Small Price current meters, the contact 
facility within such chambers was so designed as to 
produce just a single electrical contact for every revo?
lution of the rotor. During the period 1906 to 1908, 
however, John C. Hoyt of the Survey proposed that 
meters be supplied with an extra contact chamber 
within which a single contact would be made at each 
fifth revolution thereof. The idea of a worm-and-gear 
arrangement was borrowed from the acoustic meters 
for this purpose. 
The meter shown in Figure 93 is the very model 
which contained the first experimental "penta" con?
tact chamber. Because velocities measured during 
flood periods would often cause the rotors to revolve 
too rapidly for the operator to count the revolutions 
accurately, and because Floyt's idea could overcome 
that difficulty in a very satisfactory manner, it was 
quickly adopted. Another innovation, proposed in 
1912 by C. C. Covert, a district engineer of the Geol?
ogical Survey frcm New York State, consisted of cast?
ing a "boss" on the upper limb of the yoke into which 
a wading rod might be screwed. Streams in that State, 
as in all other northern States, are prone to freeze 
over during the winter months, and before hydrog?
raphers could measure them, they had to chop a large 
number (usually 20 or more) holes through the ice. 
By suspending the meters in this new manner, the tail?
piece of the meter could be removed, and the size of 
the holes, together with much of the arduous labor, 
could be considerably reduced. Tha t idea also met 
with approval, and the current meter shown in Fig?
ure 93 reflects Covert's innovation as well as the com?
mercial version of Hoyt's idea concerning the "penta" 
contact chambers. The meter shown in this figure is 
the last of the Small Price meters presently in the 
Smithsonian collection, a collection which reflects 
practically all of the improvements in the vertical-
axis, cup-type models from their first conception up 
to those made in 1925. Since then, only a few minor 
innovations have been added. The pivots on which 
their rotors have revolved, for example, have since 
had their lengths changed three times, with the long?
est of the lot being the present favorite. The only 
other change consisted of incorporating both the 
"single contact" and "penta contact" features within 
a single contact chamber having two electrical binding 
posts. Since that idea was adopted, hydrographers 
have needed only to connect the lead wire to whichev?
er terminal best suited their needs. A modern Small 
Price meter, provided with all of those latest innova?
tions appears in Figure 94. 
When undertaking a study of current meters such 
as this, one cannot help being impressed with the 
persistence with which each new design tenaciously 
hangs on throughout the years. Rod floats such as 
introduced by Leonardo da Vinci, for example, are 
NUMBER 28 87 
FIGURE 94.?A Small Price current meter of the type now in use. 
(Property of the U.S. Geological Survey; photo by A. H. Frazier.) 
still being used under certain special conditions, and 
the same circumstances prevail with respect to prac?
tically all of the other instruments discussed here. 
In this connection, it should be explained that no 
attempt has been made to discuss the complete variety 
of devices that are known to have been used for meas?
uring streamflow. During recent years especially, elec?
tromagnetic, electronic, acoustic, optical, photo?
graphic, radioactive, chemical, and a host of other 
methods have been developed, but none of them have 
yet replaced the conventional, mechanical type of 
water current meters, nor have any of them achieved 
any high degree of popularity. No doubt more than 
95 percent of the streamflow measurements through?
out the world are presently being made with mechan?
ical current meters, such as the more modern models 
that have been described here. They are simple in con?
struction, easy to operate, rugged, easy to repair, con?
venient to transport from one river to another, and 
are relatively inexpensive. It seems unlikely that they 
will become obsolete for many years to come. 
NOTES 
' SINGER, "From Early Times," page 521. 
' FRAZIER, "William Gunn Price." 
3
 BISWAS, History of Hydrology, page 20. 
* NOBLECOURT, "Tutankhamun's Golden Trove," page 632. 
6
 CLICK, "Medieval Irrigation Clocks," pages 424-428. 
* SCIIAACK, "Vergangenheit, Gegenwart," page lOfF. 
' JACOBSEN and LLOYD, Sennacharib's Aqueduct at Jer-
wan. 
" HERSCHEL, Frontinus and the Water Supply, page 27. 
"Ibid, page 202. 
" C O H E N and DRABKIN, A Souue in Greek Science, page 
241. See also Truesdell, "The First Engineer," page 16. 
" F O N T A N A , Dell' Accrescimento, pages 15-61, as trans?
lated by the Engineering Societies Library, New York. 
"Ibid . , page [21] , as translated by the Engineering So?
cieties Library, New York. 
" SALUSBURY, Mathematical Collections and Translations, 
pages 9-12. 
* GILLISPIE, Dictionary, pages 115-116. 
16
 POGGENDORFF, Geschichte der Physik, page 319. 
16
 SALUSBURY, op. cit. 
" D R A K E , Discoveries and Opinions of Galileo, page 115. 
18
 GILLISPIE, op. cit., pages 115-116. 
" PARSONS, Engineers and Engineering, page 329. 
20
 W O L F , History of Science, page 540. 
21
 GILLISPIE, op. cit. 
a
 SALUSBURY, op. cit. 
" Ibid., page 48. 
24
 Ibid., page 24. 
29
 Ibid., pace 49. 
20
 Ibid., page 6. 
27
 DA VINCI, Manuscript "A" folio 42 V. 
28
 MARINONI, "Tempo Armonico," pages 45-48. 
2B
 MACCURDY, The Notebooks of Leonardo da Vinci, 
page 526. 
m
 MASETTI, "Descrizione, Esamc e Teoria," page 410. 
SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 
31
 H U M P H R E Y S and ABBOT, Report Upon the Physics and 
Hydraulics," page 225. 
32
 AGRIPPA, Nuove Inventione di Camillo Agrippa. 
83
 ANONYMOUS, "The Life of Monsieur Guglielmini," 
page 177. 
34
 GUGLIELMINI, Opera Omnia, pages 190-195. 
35
 SANTORIO, Commentaria In Primam, pages 345-346. See 
also FRAZIER, "Dr. Santorio's Water Current Meter," pages 
249-253. 
30
 BRUNING, Verhandlingen. 
37
 WOLTMAN, Theorie und Gebrauch, page 3, table 3. 
38
 GRANGER, Vitruvius on Architecture, pages 323-325. 
39
 MILANESE, "Dr. Santorio's Water Current Meter," 
pages 6866-6867. 
40
 MICHELOTTI , Sperimenti Idraulici. 
" R O U S E and INCE, History of Hydraulics, page 130. 
41
 BREWSTER, The Edinburgh Encyclopaedia, pages 
761-762. 
4 3DUBUAT, Principes d'Hydraulique, page 155, as trans?
lated by John Macedonia. 
44
 Ibid., page 319. 
48
 BREWSTER, in FERGUSON, Lectures on Select Subjects, 
page 37, plate 1, figure 8. 
46
 MASETTI , op. cit., page 417, as translated by Dr. Carlo 
Zammattio and A. H. Frazier. 
47
 These tests are more fully described in BEARD'S article, 
"Practical Observations on the Power Expended in Driving 
the Machinery of a Cotton Manufactory at Lowell." 
48
 Cf. FRIZELL, "The Water-Power of the Falls of St. An?
thony," pages 423-424. 
49
 PITOT, "D'une Machine pour measurer." 
50
 As translated in R O U S E and INCE, History of Hydraulics, 
page 116. 
61
 TROSKOLANSKI, Hydromttry, pages 425-445. 
81
 PARSHALL, "The Improved Venturi Flume," pages 
841-880. 
83
 TAYLOR, The Mathematical Practitioners, page 426. 
84
 U S H E R , A History of Mechanical Inventions, page 324. 
88
 D E SAUMAREZ, "V. An Account of a New Machine," 
page 411. 
86
 W O L F , op. cit., opposite page 63. 
87
 D E SAUMAREZ, Account of . . . Henry De Saumarez, 
page 4. 
88
 D E SAUMAREZ, " I I I . A Further Account of a New Ma?
chine," "IV. Observations upon the Tides," and "V. An 
Account of a New Machine." 
88
 SAFFORD and HAMILTON, "The American Mixed-flow 
Turbine," page 1241, figures 5 and 6. 
00
 D E SAUMAREZ, " I I I . A Further Account of a New Ma?
chine," "IV. Observations upon the Tides," and "V. An 
Account of a new Machine." 
41
 SMEATON, "LXX. An Account of Some Experiments." 
62
 D E SAUMAREZ, Account of . . . Henry De Saumarez. 
63
 Ibid., page 3. 
04
 SPENCER, "Notes," page 214. 
68
 D E SAUMAREZ, Account of . . . Henry De Saumarez, 
page 8. 
60
 Ibid., page 13. 
67
 Ibid., page 16. 
08
 H O O K E , "A Way-wiser for Sea," pages 84-85. 
09
 FRAZIER, "Joseph Saxton," pages 47-48. 
70
 Saxton diary, Smithsonian Institution Archives, 25 May-
23 August 1832. 
71
 GREAT BRITAIN, PARLIAMENTARY PAPERS, Report from 
the Select Committee, pages 175-176. 
" H A S K O L L , The Practice of Engineering Field Work, 
page 261. 
73
 H U M P H R E Y S and ABBOT, op. cit., appendix G, pages 
cxxiv-cxxv. 
" T h e appellation of the "U.S. Coast Survey" was 
changed by an act of Congress, 20 June 1878, to the "U.S. 
Coast and Geodetic Survey." See WEBER, Coast and Geod?
etic Survey. 
78
 PAYSON, "Current-Observations," pages 1304-1318. 
76
 H U M P H R E Y S and ABBOT, op. cit., page 225. 
77
 FRAZIER, "Daniel Farrand Henry," pages 541-565. 
78
 U.S. ARMY CORPS OF ENGINEERS, Annual Report, 
page 621. 
79
 BAUMGARTEN, "Sur le moulinet de Woltman," pages 
326-357, and VENTUROLI, Elementi di Mechanica e Hyd-
raulica, page 160. 
80
 U.S. H O U S E OF REPRESENTATIVES, "Report of Gen. 
Theodore G. Ellis," pages 304-309. 
81
 Ibid., pages 306-307. 
8 2STEARNS, "On the Current Meter." 
83
 GRUNSKY, "Appendix," page 80. 
84
 Ibid. 
83
 HASKELL, "Reminiscences," page 234. 
86
 FRAZIER, "Embudo, New Mexico." 
87
 HOYT and GROVER, River Discharge, page 7. 
88
 FRAZIER, "Daniel Farrand Henry," pages 541-565. 
89
 HENRY, United States International Exhibition, 1876, 
page 191. 
90
 U.S. H O U S E OF REPRESENTATIVES, "Appendix A," pages 
304-355. 
91
 FRAZIER, "William Gunn Price," page 51. 
92
 NETTLETON, Report of the State Engineer, page 8. 
93
 FRAZIER, "William Gunn Price." 
94
 Files of Chief Hydrologist, U.S. Geological Survey, 
Washington, D.C. 
88
 W. & L.E. Gurley files, Troy, New York. 
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Index 
Abbot current meter, 56, 63 
Abbot, Gen. Henry L., 14, 54, 56, 63 
Academy of Sciences, Paris, 25, 43, 57 
Acoustic current meter, 82 
Adelaide Gallery (London), 52, 53 
Adjutage, 4, 33 
Aggeler, Cecil, 39 
Agrippa, Camillo, 15 
Akhenaten (Pharaoh), 2 
Akron (Ohio) Repository, 51 
Alger, Horatio, 51 
American Philosophical Society, 53 
American Society of Civil Engineers, 74 
Anemometer, 20, 50 
Appomattox, 74 
Aqueducts, 4, 6 
Arizona, State of, 77 
Arno River (Italy), 7 
Austrian Institute of Civil Engineers, 50 
Babb, C C , 83 
Bache, A. D., 53 
Bailey current meter, 78 
Balance scales, 53 
Baldwin, James Fowle, 30 
Baldwin, Loammi, 30 
Barattieri, G. B., 13 
Batchelder, Samuel, 28 
Baumgarten, Andre Gustave Adolphe, 56-59 
Baumgarten current meter, 56-64, 74 
Beard, Ithamar A., 28-31 
Bentzel, Carl E., 35 
Bentzel velocity tube, 35-36 
Berger, C L. & Sons, 61 
Bibliography of Hydrometry, 56 
Bi-filar suspension, 51 
Black Friars, Order of, 7 
Black Sea, 24 
Bligh, Captain William, 45 
Bohemia, 69 
Bologna (I taly) , 16 
Bors, 20 
Bosporus, Strait of, 22 
Boston and Lowell Railroad, 30 
Bounty, H.M.S., 45 
Brewster, Sir David, 26 
British Association for the Advancement of Science, 26, 50 
British House of Commons, 41 
British National Maritime Museum, 45 
British Parliament, 41 
Brookline (Mass.), 65 
Brooklyn (N.Y.), 30 
Brunacci, Vincenzio, 13 
Brunings, Christiaan, 21 
Buff and Berger, 62-63, 75 
Buff, George Louis, 61 
Cabeo, Nicola, 13 
California, 63, 
Castelli, Benedetto, 6-8 
Centennial Commission, 74 
Chaseville (N.Y.), 78 
Chevy Chase Lake (Md.) rating station, 83 
Code of Hammurabi, 2 
Codice Atlantico, 9 
Colne River (England), 53 
Colorado Agricultural Experiment Station, 40 
"Colorado" current meter, 77 
Colorado Springs, 76 
Concord River, 28 
Cone, Victor Mann, 40 
Connecticut River, 14, 58, 74 
Conte, 57 
Commissioners of the Admiralty, 47 
Component rotor, 70 
Continuity of flow, 8 
Coradi, G., 68 
Cornell University, 66 
Corps of Engineers, U.S. Army. See U.S. Corps 
of Engineers 
Covert, C C , 86 
Covert yoke, 86 
Croatia, 20 
Cubitt, Joseph, 53 
Cubitt, William, 53 
Cuxhaven (Germany), 50 
Danube River, 24 
Darcy, Henri P.G ., 34 
Dark Ages, 5 
Da Vinci, Leonardo, 8-13, 37, 48 
Deane, Zacharia, 75 
Denver (Colo.), 66, 77-78 
Department of the Interior. See U.S. Department of 
the Interior 
De Saumarez, Henry, 41-47 
Detroit (Mich.) , 64, 83 
Direction-indicating facility, 65, 81 
Double floats, 8. See also Floats 
Dubuat, P. L. G , 24-27 
Dummer, John, 28 
Dutch Academy of Sciences, 21 
Ecole des Ponts et Chaussees, 21, 30, 56 
Eddystone lighthouse, 45 
Edinburgh Encyclopaedia, 26 
Egypt, 2 
Elementi di Mechanica e Hydraulica, 56 
Elliott Bros. (London), 50, 53, 68 
Ellis current meter, 74-75, 79 
Ellis, Gen. Theodore C , 14, 58-59 
Embudo (N. Mex . ) ,66 , 78 
England, 30, 50, 68 
92 
NUMBER 28 93 
Englewood (N.J.) , 78 
English channel, 44-45, 50 
E. S. Ritchie and Sons, 65-67 
Estonia, 69 
Ferguson, James, 27 
Floats, 8-17. See also Double floats, Free floats, Rod floats 
Florence (Italy), 7 
Florida, State of, 65 
Focacci current meter, 36-37, 72 
Focacci, Francesco, 36 
Fontana, Giovan, 6-7 
Fort Collins (Colo.), 40 
Fort Shelby Hotel, 83 
Fossombroni, Vittorio, 36 
Fourcroy, de, 25 
France, 24 
Francis, James, 14, 31, 61-63 
Franklin Institute (Philadelphia, Pa.) , 51, 75 
Frederick (Md.) , 51 
Free floats, 8-14. See also Floats 
Frontinus, 4, 6-7 
Fteley, Alphonse, 59-61 
Fteley-Stearns current meter, 59-61, 77 
Gaging stations, 1 
Galileo, 6-8, 16 
Garonne River (France), 56, 58 
Gauthey, Edmund Marie, 21 
Geological Survey. See U.S. Geological Survey 
Germany, 68-70 
Ghadames (Oasis), 3 
Golden Gate Park (San Francisco), 63 
Great Exhibition (London), 53 
Great Lakes, 56, 73-74 
Greeley, Horace, 75 
Grover, Nathan C , 78 
Guernsey, Island of, 41 
Guglielmini, Domenico, 15-17, 24 
Gulf Stream, 65 
Gurley, W. & L. E., 81-85 
Hall current meter, 78 
Hall, William Hammond, 63-64, 67, 78 
Halley, Edmund, 46 
Hamilton canal, 28, 31 
Hamilton mills, 28, 29 
Hammurabi, 2 
Harlacher, Andreas R., 69 
Harlacher current meter, 69 
Hartford (Conn.), 74 
Haskell current meter, 78, 83 
Haskell, Eugene E., 64-67, 78 
Haskoll, W. Davis, 53 
Henry current meter, 56, 58, 73-75 
Henry, Daniel Farrand, 56, 58, 73-75, 83 
Henry, Joseph, 74 
Hero of Alexandria, 4-5, 29 
Herschel, Clemens, 37, 58, 61-62, 74, 78 
Herschel current meter, 78 
Hooke current meter, 48-50, 72 
Hoover Dam, 77 
Horizontal-axis meters, 48-71 
House of Commons, 41 
Hoyt, John C , 86 
Humphreys, A. A., 14, 54, 58, 73 
Humphreys and Abbot Report, 73-74 
Hyde Park (London), 45 
Hydroelectric power, 1 
Hydrometry, 16, 36 
Independence Hall, 52 
Integration method, 50-51 
International Boundary and Water Commission, 21 
Irrigation, 1 
Irrigation Survey. See U.S. Irrigation Survey 
Italian Royal Academy of Sciences, 16, 36 
Jerwan (Iraq) , 4 
Keeler, Karl Fairbanks, 20-21 
Kempten (Germany), 68 
Knoxville (Pa.) , 78 
Kolupaila, Steponas, 56, 69-71 
Lake Mead (Nevada), 77 
Lake Trasimeno (Italy), 7 
Lallie and Bailey, 78 
Lallie, J. S. J., 78 
La Plata estuary, 50 
Large Price current meters, 81-82 
Leach, Captain Smith H., 78-79 
Leonardo da Vinci. See Da Vinci, Leonardo 
Lerebours et Secretan (Paris), 57-58, 68 
Lerebours, Marc, 58, 74 
Leupold and Stevens, Inc., 21, 35 
Lithuania Hydrometric Bureau, 69 
Litigations, 1 
Log line, 47 
Logs. See Ships' logs 
London, 41, 50, 52-53, 68 
Longitude, 41 
Lords Commissioners of the Admiralty, 47 
Louis xiv, 43 
Lowell (Mass.), 14, 28-32, 60-62 
Lowell Courier, 29 
Lukens, Isaiah, 52 
Magazine of Popular Science, 53 
Manitou (Colo.), 76 
Marine surveyors, 41, 45 
Marinoni, Augusto, 8 
Mariotte, Edme, 13, 41 
Marmora, Sea of, 24 
Marsili, Luigi Ferdinando, 22-24 
Martin, John, 53 
Mead, Ellwood, 77 
Merrimack River, 28 
Michelotti, Francesco Domenico, 24 
Milan (Italy), 24, 68 
Milanese, Ferdinando, 24 
Military Academy (U.S.), 30 
94 SMITHSONIAN STUDIES IN HISTORY AND TECHNOLOGY 
Mississippi River, 14, 21, 64-65, 78-81 
Mississippi River Commission, 64-65, 78-82 
Missouri River, 78, 82 
Mitchell, Henry, 65 
Monte Casino Monastery, 7 
Moore, Benjamin Theophilus, 68 
Moore's current meter, 67-68 
Munich (Germany), 68 
National Academy of Sciences, 53 
National Bureau of Standards, 53 
National Museum of History and Technology, 1 
Navy Department. See U.S. Navy Department 
Nesselwang (Bavaria), 68 
Nettleton, Edwin S., 75-78 
Newell, Frederick Haynes, 83 
Newton, Sir Isaac, 41, 47 
New York harbor, 65 
Nicholas, Czar of Russia, 30 
Oases, 3 
Odometer, 8 
Office of Weights and Measures, 53-54 
Ohio River, 78 
O'Neill (Nebr.), 82 
Orifices, 11, 33 
Ott, A., firm of, 68-69 
Ott, Albert, 69 
Ott current meters, 68-7J 
Ott, Herman, 69 
Ott, Ludwig, 69 
Paddles, 16-21 
Paddle wheels, 21-32 
Padua (Italy), 16 
Paducah (Ky.) , 78-79 
Parana River, 50 
Parshall, Ralph Leroy, 40 
Parsons, Dr., 30 
Parsons, William Barclay, 7 
Patent Office (Great Britain), 47 
Patterson, R. M., 53 
Paul, Edwin Geary, 83-84 
Payson, Lt. A. H., 55-56 
Peale, Franklin, 53 
"Penta" contact chamber, 86 
Perkins, Jacob, 53 
Persian windmill, 72, 73 
Perugia (Italy), 6-7 
Philadelphia (Pa.) , 51-53, 74 
Philadelphia Mint, 53 
Pisa (Italy), 7 
Pitot, Henri de, 34 
Pitot tube, 24, 33-34, 37 
Poggendorf, 7 
Point Pleasant (Mo.) , 65 
Poleni, Marquis Giovanni, 37 
Poncelot, Jean Victor, 57 
Ponts et Chaussees. See Ecole des Pontes et Chaussees 
Pope Urban vm, 7 
Powell, John Wesley, 66 
Price acoustic current meter, 82-83 
Price current meters, 75, 78-87 
Price, William Gunn, 75, 78-87 
Prismatic Club, 73 
Proprietors of Locks and Canals, 28, 31, 54, 56, 60-61, 63 
Q = A, 4, 6-8 
Q = AV, 5, 8 
Quadrant and ball, 15-17, 24 
Quinaria, 4, 33 
Rating of current meters, 50, 53 
Raynolds, Gen. William F., 56, 73-74 
Renaissance, 8 
Repository (Akron, Ohio) , 51 
Revy current meter, 50-51, 68 
Revy, Julien John, 50-51 
Riefler, Clemens, 68 
Rio Grande, 66 
Ritchie, E. S., 65 
Ritchie, E. S. and Sons, 66-67 
Ritchie-Haskell direction current meter, 66 
Robinson anemometer, 73 
Rod float, 8-11, 13-14. See also Floats 
Rohwer, Carl, 40 
Roman aqueducts, 4, 6-7, 33 
Rome, 6-7 
Rosedale (Miss.), 81 
Rouse, Hunter, 24, 34 
Royal Institution (London), 53 
Royal Society of Edinburgh, 26 
Royal Society of France, 34, 43 
Royal Society of London, 26, 43, 45-48 
Russia, 30 
Safford, Arthur T., 43, 60-61 
Saint James Park (London), 41 
Saint Petersburg (Russia), 30 
Salusbury, Thomas, 6 
San Francisco, 56, 63-64 
Santorio, Santorio, 16, 20-21 
Saxton current meter, 17, 53-56, 63, 68 
Saxton, Joseph, 51-56 
Schaak, Martin, 3 
Schenevus (N.Y.), 78 
Scott, W. E. and Co., 77 
Secretan (Paris), 56 
Sellers, Coleman, 53 
Sennacherib, 4 
Serviss, J. H., 78 
Sexton, George, 51 
Ships' logs, 14-15, 41-49, 68 
Small Price current meters, 67, 83-87 
Smeaton, John, 45 
Smithsonian Institution, iii-iv, 26, 45, 50, 54, 56, 61, 63-64, 
68, 73-74, 78-79, 82-83, 86 
South America, 50 
"Square inch" method, 33 
S-rotor, 37 
Standards (U.S.) , 53 
NUMBER 28 95 
Stearns, Frederick P., 59-61 
Stephenson steam locomotives, 30 
Stimson, Eugene K., 76 
Storrow, Charles S., 30-32 
Stout, Prof. O. V. P., 83 
Subsurface direction meter, 81 
Sudbury River, 59-60 
Survey of the Northern and Northwestern Lakes, 61 
Sussex Street (London), 53 
Technology and Culture, 73 
Tel 'Armarna (Egypt), 2 
Tethered floats, 8. See also Floats 
Thames estuary, 43-44, 47 
Thames River (England), 68 
Tiber River (Italy), 6, 56 
Tolotti, Antonio Sempiterni, 72 
Tolotti current meter, 72-73 
Trasimeno Lake (Perugia, Italy), 7 
Tredgold, Thomas, 37 
Trieste (Italy), 20 
Trinity House (London), 47 
Trowbridge, Prof. William P., 54 
Troy (N.Y.), 81, 83 
Tubing applications, 33-40 
Tutankhamun (Pharaoh), 2 
Turin (Italy), 24 
Union Colony, 76 
United Nations, 40 
University College (London), 53 
University of Nebraska, 83 
University of Notre Dame, 70 
Uruguay River, 50 
U. S. Army, 58 
U. S. Coast and Geodetic Survey, 50, 65 
U. S. Coast Survey, 53-54 
U. S. Corps of Engineers, 58, 63-64, 74-75, 78 
U. S. Department of Agriculture, 40 
U. S. Department of the Interior, 66, 83 
U. S. Geological Survey, 1, 50, 64, 66-67, 69, 78, 82-83 
U. S. International Exhibition, 1876, 74 
U. S. Irrigation Survey, 64, 66-67, 78, 83 
U. S. Lake Survey, 56, 58, 64, 73, 75 
U. S. Mint, 53 
U. S. Navy Department, 66, 78 
U. S. Waterways Experiment Station, 35 
Velocity distribution, 8-11 
Venice (Italy), 16 
Venturi flumes, 40 
Venturi, Giovanni Battista, 11, 37-39 
Venturi tubes, 37-40 
Venturoli, Giuseppi, 56 
Vertical-axis meters, 72-87 
Vertical velocity curve, 16-17, 36 
Vicksburg (Miss.), 81 
Vienna (Austria), 68 
Vitruvius, 4, 22 
Vowles, Hugh F., 73 
Warren, General G. K., 74 
Washington, State of, 83 
Washington, D. C , 53, 83 
Water masters, 1 
Water Resources Branch, 67, 69, 83 
Watkins and Hill (London), 53 
Way-wiser for sea, 48 
Weirs, 40 
Western Canal (Lowell, Mass.), 31 
Westfield (Mass.), 51 
Wheatstone Bridge, 53 
Wheatstone, Charles, 53 
Whistler, George Washington, 29-32 
Windsor (Conn.), 51 
Wolf, Abraham, 7, 13 
Woltman current meter, 68 
Woltman, Reinhard, 21, 49-50 
World Meteorological Organization, 40 
Ximenes, Leonardo, 21 
Yakima (Wash.), 83 
Yoke, Covert. See Covert yoke 
Yugoslavia, 20 
Zammattio, Carlo, 8, 20 
Zurich (Switzerland), 68 
it U.S. GOVERNMENT PRINTING OFFICE; 1974 O?527-777