SMITHSONIAN MISCELLANEOUS COLLECTIONSVOLUME 76. NUMBER 2
HISTORY OF ELECTRIC LIGHT
BYHENRY SGHROEDERHarrison, New Jersey
PER\ ^"^^3^ /ORB
(Publication 2717)
CITY OF WASHINGTONPUBLISHED BY THE SMITHSONIAN INSTITUTIONAUGUST 15, 1923
Zrtie Boxb QSaftitnore (prceeBALTIMORE, MD., U. S. A.
CONTENTS PAGEList of Illustrations vForeword ixChronology of Electric Light xiEarly Records of Electricity and Magnetism iMachines Generating Electricity by Friction 2The Leyden Jar 3Electricity Generated by Chemical Means 3Improvement of Volta's Battery 5Davy's Discoveries 5Researches of Oersted, Ampere, Schweigger and Sturgeon 6Ohm's Law 7Invention of the Dynamo 7Daniell's Battery 10Grove's Battery 11Grove's Demonstration of Incandescent Lighting 12Grenet Battery 13De Moleyns' Incandescent Lamp 13Early Developments of the Arc Lamp 14Joule's Law 16Starr's Incandescent Lamp 17Other Early Incandescent Lamps 19Further Arc Lamp Developments 20Development of the Dynamo, 1840-1860 24The First Commercial Installation of an Electric Light 25Further Dynamo Developments 27Russian Incandescent Lamp Inventors 30The Jablochkofif " Candle " 31Commercial Introduction of the Differentially Controlled Arc Lamp ^3Arc Lighting in the United States 3;^Other American Arc Light Systems 40
" Sub-Dividing the Electric Light " 42Edison's Invention of a Practical Incandescent Lamp 43Edison's Three-Wire System 53Development of the Alternating Current Constant Potential System 54Incandescent Lamp Developments, 1884-1894 56The Edison " Municipal " Street Lighting System 62The Shunt Box System for Series Incandescent Lamps 64The Enclosed Arc Lamp 65The Flame Arc Lamp 67The Constant Current Transformer for Series Circuits 69Enclosed Series Alternating Current Arc Lamps 69Series Incandescent Lamps on Constant Current Transformers 70The Nernst Lamp 71The Cooper-Hewitt Lamp 72The Luminous or Magnetite Arc Lamp 74Mercury Arc Rectifier for Magnetite Arc Lamps yyill
IV CONTENTS
PAGEIncandescent Lamp Developments, 1894-1904 78The Moore Tube Light 79The Osmium Lamp 82The Gem Lamp 82The Tantalum Lamp 84Invention of the Tungsten Lamp 85Drawn Tungsten Wire 87The Quartz Mercury Vapor Arc Lamp 88The Gas-Filled Tungsten Lamp 89Types and Sizes of Tungsten Lamps Now Made 91Standard Voltages 93Cost of Incandescent Electric Light 93Statistics Regarding the Present Demand for Lamps 94Selected Bibliography 95
LIST OF ILLUSTRATIONS PACEPortion of the Electrical Exhibit in the UniLed States National Museum. . viiiOtto Von Guericke's Electric Machine, 1650 2Voltaic Pile, 1799 4Faraday's Dynamo, 1831 8Pixii's Dynamo, 1832 9Daniell's Cell, 1836 10Grove's Cell, 1838 nGrove's Incandescent Lamp, 1840 13De Moleyns' Incandescent Lamp, 1841 14Wright's Arc Lamp, 1845 15Archereau's Arc Lamp, 1848 16Starr's Incandescent Lamp, 1845 18Staite's Incandescent Lamp, 1848 19Roberts' Incandescent Lamp, 1852 19Farmer's Incandescent Lamp, 1859 20Roberts' Arc Lamp, 1852 21Slater and Watson's Arc Lamp, 1852 21Diagram of " Differential " Method of Control of an Arc Lamp 22Lacassagne and Thiers' Differentially Controlled Arc Lamp, 1856 23Serrin's Arc Lamp, 1 857 24Siemens' Dynamo, 1856 25Alliance Dynamo, 1862 26Wheatstone's Self-Excited Dynamo, 1866 27Gramme's Dynamo, 1871 28Gramme's " Ring " Armature 28Alteneck's Dynamo with " Drum " Wound Armature, 1872 29Lodyguine's Incandescent Lamp, 1872 30Konn's Incandescent Lamp, 1875 30Bouliguine's Incandescent Lamp, 1876 31Jablochkoff " Candle," 1876 2~Jablochkoff's Alternating Current Dynamo, 1876 2^Wallace-Farmer Arc Lamp, 1875 34Wallace-Farmer Dynamo, 1875 34Weston's Arc Lamp, 1876 35Brush's Dynamo, 1877 36Diagram of Brush Armature 36Brush's Arc Lamp, 1877 7,yThomson-Houston Arc Dynamo, 1878 38Diagram of T-H Arc Lighting System 39Thomson-Houston Arc Lamp, 1878 40Thomson Double Carbon Arc Lamp 40IMaxim Dynamo 41Sawyer's Incandescent Lamp, 1878 42Farmer's Incandescent Lamp, 1878 42Maxim's Incandescent Lamp, 1878 43Edison's First Experimental Lamp, 1878 44
VI LIST OF ILLUSTRATIONS
PAGEDiagram of Constant Current Series System 45Diagram of Edison's Multiple System, 1879 45Edison Dynamo, 1879 46Edison's High Resistance Platinum Lamp, 1879 47Edison's High Resistance Platinum in Vacuum Lamp, 1879 47Edison's Carbon Lamp of October 21, 1879 48Demonstration of Edison's Incandescent Lighting System 49Dynamo Room, S. S. Columbia 50Original Socket for Incandescent Lamps 51Wire Terminal Base Lamp, 1880 51Original Screw Base Lamp, 1880 52Improved Screw Base Lamp, 1881 52Final Form of Screw Base, 1881 53Diagram of Edison's Three Wire System, 1881 54Diagram of Stanley's Ahernating Current Multiple System, 1885 55Standard Edison Lamp, 1884 56Standard Edison Lamp, 1888 56Standard Edison Lamp, 1894 57Various Bases in Use, 1892 58Thomson-Houston Socket 59Westinghouse Socket 59Adapters for Edison Screw Sockets, 1892 60Various Series Bases in Use, 1892 61Edison " Municipal " System, 1885 62Edison " Municipal " Lamp, 1885 63Shunt Box System, 1887 64Enclosed Arc Lamp, 1893 65Open Flame Arc Lamp, 1898 66Enclosed Flame Arc Lamp, 1908 66Constant Current Transformer, 1900 68Series Incandescent Lamp Socket with Film Cutout, 1900 70Nernst Lamp, 1900 71Diagram of Nernst Lamp 72Cooper-Hewitt Mercury Vapor Arc Lamp, 1901 ']2^Diagram of Cooper-Hewitt Lamp for Use on Alternating Current 74Luminous or Magnetite Arc Lamp, 1902 75Diagram of Series Magnetite Arc Lamp 'j(SMercury Arc Rectifier Tube for Series Magnetite Arc Circuits, 1902 "/]Early Mercury Arc Rectifier Installation 78The Moore Tube Light, 1904 79Diagram of Feeder Valve of Moore Tube 80Osmium Lamp, 1905 , 82Gem Lamp, 1905 83Tantalum Lamp, 1906 84Tungsten Lamp, 1907 86Drawn Tungsten Wire Lamp, 191 1 87Quartz Mercury Vapor Lamp, 1912 88Gas Filled Tungsten Lamp, 1913 89Gas Filled Tungsten Lamp, 1923 90Standard Tungsten Lamps, 1923 92

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FOREWORDIn the year 1884 a Section of Transportation was organized inthe L'nited States National Museum for the i)uri)ose of preparingand assemhhng educational exhihits of a few ohjects of railroadmachinery which had been obtained both from the Centennial Exhi-bition held in Philadelphia in 1876 and still earlier as incidentals toethnological collections, and to secure other collections relating to therailway industry.From this beginning the section was expanded to include thewhole field of engineering and is designated at present as the Divisionsof Mineral and Mechanical Technology. The growth and enlarge-ment of the collections has been particularly marked in the fields ofmining and mineral industries ; mechanical engineering, especiallypertaining to the steam engine, internal combustion engine and loco-motive ; naval architecture, and electrical engineering, particularly thedevelopment of the telegraph, telephone and the electric light.In the acquisition of objects visualizing the history of electriclight the Museum has 1)een rather fortunate, particularly as regardsthe developments in the United States. Thus mention may be madeof the original Patent Office models of the more important dvnamos.arc lights and incandescent lights, together with original commercialapparatus after these models ; a unit of the equipment used in the firstcommercially successful installation on land of an incandescent lightingsystem, presented by Joseph E. Hinds in whose engraving establish-ment in New York City the installation was made in 1881 ; and a largeseries of incandescent lights, mainly originals, visualizing chrono-logically the developments of the Edison light from its inception, pre-sented at intervals since the year 1898 by the (General ElectricCompany.The ()I)ject of all collections in the Divisions is to visualize broadlythe steps by which advances have l)een made in each field of engineer-ing ; to show the layman the fundamental and general principles whichare the l)asis for the developments : and to familiarize the engineerwith branches of engineering other than his own. Normally when asubject is completely covered by a collection of objects, a paper is pre-pared and published descril)ing the collection and the story it portrays.In the present instance, however, on account of the uncertainty of
X FOREWORD
the time of completing the collection, if it is possible ever to bring thisabout, it was thought advisable to publish Mr. Schroeder's paperwhich draws upon the Museum collection as completely as possible.Carl W. Mitman,Curator, Divisions of Mineral andMechanical Technology,U. S. National Muscmn^.
CHRONOLOGY OF ELECTRIC LIGHT1800—Allesandro Volta demonstrated his discovery that electricitycan be generated by chemical means. The Volt, the unitof electric pressure, is named in his honor for this discoveryof the electric battery.1802—Sir Humphry Davy demonstrated that electric current can heatcarbon and strips of metal to incandescence and give light.1809—Sir Humphry Davy demonstrated that current will give a bril-liant flame between the ends of two carbon pencils which arefirst allowed to touch each other and then pulled apart. Thislight he called the '' arc " on account of its arch shape.1820—Andre Marie Ampere discovered that current flowing througha coiled wire gives it the properties of a magnet. The Am-TERE, the unit of flow of electric current, is named in hishonor for this discovery.1825—Georg Simon Ohm discovered the relation between the voltage,ampereage and resistance in an electric circuit, which iscalled Ohm's Law. The Ohm, the unit of electric resis-tance, is named in his honor for this discovery.183 1—Michael Faraday discovered that electricity can be generatedby moving a wire in the neighborhood of a magnet, theprinciple of the dynamo.1840—Sir William Robert Grove demonstrated his experimentalincandescent lamp in which platinum is made incandescentby current flowing through it.1 84 1—Frederick De Moleyns obtained the first patent on an incan-descent lamp. The burner was powdered charcoal operatingin an exhausted glass globe.1845—Thomas Wright obtained the first patent on an arc light.1845—J- ^^- Starr invented an incandescent lamp consisting of acarbon pencil operating in the vacuum above a column ofmercury.1856—Joseph Lacassagne and Henry Thiers invented the " differen-tial " method of control of the arc which was universallyused twenty years later when the arc lamp was commerciallyestablished.1862—The first commercial installation of an electric light. An arclight was put in a lighthouse in England.
XII CHRONOLOGY OF ELECTRIC LIGHT1866—Sir Charles Wheatstone invented the " self-excited " dynamo,now universally used.1872—Lodyguine invented an incandescent lamp having a graphitehurner operating in nitrogen gas.1876—Paul Jablochkoff invented the "electric candle," an arc lightcommercially used for lighting the boulevards in Paris.1877-8—Arc light systems commercially established in the UnitedStates by William Wallace and Prof. Moses Farmer, EdwardWeston, Charles F. Brush and Prof. Elihu Thomson andEdwin J. Houston.1879—Thomas Alva Edison invented an incandescent lamp consistingof a high resistance carbon filament operating in a highvacuum maintained by an all glass globe. These principlesare used in all incandescent lamps made to-day. He alsoinvented a completely new system of distributing electricityat constant pressure, now universally used.1882—Lucien Goulard and John D. Gibbs invented a series alternat-ing current system of distributing electric current. This hasnot been commercially used.1886—William Stanley invented a constant pressure alternating cur-rent system of distribution. This is universally used wherecurrent is to be distributed long distances.1893—Louis B. Marks invented the enclosed carbon arc lamp.1898—Bremer's invention of the dame arc lamp, having carbons im-pregnated with various salts, commercially established.1900—Dr. Walther Nernst's invention of the Nernst lamp commer-cially established. The burner consisted of various oxides,such as zirconia, which operated in the open air.1901—Dr. Peter Cooper Hewitt's invention of the mercury arc lightcommercially established.1902—The magnetite arc lamp was developed by C. A. B. Halvorson,Jr. This has a new method of control of the arc. Thenegative electrode consists of a mixture of magnetite andother substances packed in an iron tube.1904—D. McFarlan Moore's invention of the Moore vacuum tubelight commercially established. This consisted of a longtube, made in lengths up to 200 feet, from which the aiihad been exhausted to about a thousandth of an atmosphere.High voltage current passing through this rarefied atmos-phere caused it to glow. Rarefied carbon dioxide gas waslater used.
CHRONOLOGY OF ELECTRIC LIGHT XIII1905-^Dr. Auer von Welsbach's invention of the osmium incandes-cent lamp Commercially established, but only on a small scalein Europe. The metal osmium, used for the filament whichoperated in vacuum, is rarer and more expensive than plati-num.1905—Dr. Willis R. Whitney's invention of the Gem incandescentlamp commercially established. The carbon filament hadbeen heated to a very high temperature in an electric resis-tance furnace invented by him. The lamp was 25 per centmore eflficient than the regular carbon lamp.1906—Dr. Werner von Bolton's invention of the tantalum incandes-cent lamp commercially established.1907—Alexander Just and Franz Hanaman's invention of the tungs-ten filament incandescent lamp commercially established.191 1—Dr. William D. Coolidge's invention of drawn tungsten wirecommercially established.1913—Dr. Irving Langmuir's invention of the gas-filled tungstenfilament incandescent lamp commercially established.

HISTORY OF ELECTRIC LIGHTBv HENRY SCHROEDER,HAPRISON, NEW JERSEY.EARLY RECORDS OF ELECTRICITY AND MAGNETISMAbout twenty-five centuries ago, Thales, a Greek philosopher,recorded the fact that if amber is rubbed it will attract light objects.The Greeks called amber " elektron," from which we get the word
" electricity." About two hundred and fifty years later, Aristotle,another Greek philosopher, mentioned that the lodestone would attractiron. Lodestone is an iron ore (Fe304), having magnetic qualitiesand is now called magnetite. The word " magnet " comes from thefact that the best specimens of lodestones came from Magnesia, acity in Asia Minor. Plutarch, a Greek biographer, wrote about100 A. D., that iron is sometimes attracted and at other times repelledby a lodestone. This indicates that the piece of iron was magnetisedby the lodestone.In 1180, Alexander Neckham, an English Monk, described thecompass, which probably had been invented by sailors of the northerncountries of Europe, although its invention has been credited to theChinese. Early compasses probably consisted of an iron needle,magnetised by a lodestone, mounted on a piece of wood floating inwater. The word lodestone or " leading stone " comes from the factthat it would point towards the north if suspended like a compass.William Gilbert, physician to Queen Elizabeth of England, wrote abook about the year 1600 giving all the information then known onthe subject. He also described his experiments, showing, amongother things, the existence of magnetic lines of force and of north andsouth poles in a magnet. Robert Norman had discovered a few yearspreviously that a compass needle mounted on a horizontal axis woulddip downward. Gilbert cut a large lodestone into a sphere, andobserved that the needle did not dip at the equator of this sphere, thedip increasing to 90 degrees as the poles were approached. Fromthis he deduced that the earth was a magnet with the magnetic northpole at the geographic north pole. It has since been determined thatthese two poles do not coincide. Gilbert suggested the use of thedipping needle to determine latitude. He also discovered that othersubstances, beside amber, would attract light objects if rubbed.Smithsonian Miscellaneous Collections, Vol. 76, No. 2
2 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. y6MACHINES GENERATING ELECTRICITY BY FRICTIONOtto \o\-\ Gnericke was mayor of the city of Magdeburg as well asa philosopher. About 1650 he made a machine consisting of a ballof sulphur mounted on a shaft which could be rotated. Electricitywas generated when the hand was pressed against the globe as itrotated. He also discovered that electricity could be conducted awayfrom the globe by a chain and would appear at the other end of thechain. Yon Guericke also invented the vacuum air pump. In 1709,Francis Hawksbee, an Englishman, made a similar machine, using a
Otto Von Guericke's Electric Machine, 1650.A ball of sulphur was rotated, electricity being generated when itrubbed against the hand.hollow glass globe which could be exhausted. The exhausted globewhen rotated at high speed and rubbed by hand would produce a glow-ing light. This " electric light " as it was called, created great excite-ment when it was shown before the Royal Society, a gathering ofscientists, in London.Stephen Gray, twenty years later, showed the Royal Society thatelectricity could be conducted about a thousand feet by a hemp thread,supported by silk threads. If metal supports were used, this could notbe done. Charles du Eay, a Frenchman, repeated Gray's experiments,and showed in 1733 that the substances which were insulators, and
NO. 2 HISTORY OF ELECTRIC LIGHT—SCHROEDER 3
which Gilbert had discovered, would become electrified if rubbed.Those substances which Gilbert could not electrify were conductorsof electricity. THE LEYDEN JARThe thought came to Von Kleist, Bishop of Pomerania, Germany,about 1745, that electricity could be stored. The frictional machinesgenerated so small an amount of electricity (though, as is now known,at a very high pressure—several thousand volts) that he thought hecould increase the quantity by storing it. Knowing that glass wasan insulator and water a conductor, he filled a glass bottle partly fullof water with a nail in the cork to connect the machine with thewater. Holding the bottle in one hand and turning the machine withthe other for a few minutes, he then disconnected the bottle from themachine. When he touched the nail with his other hand he receiveda shock which nearly stunned him. This was called the Leyden jar,the forerunner of the present condenser. It received its name fromthe fact that its discovery was also made a short time after by experi-menters in the University of Leyden. Further experiments showedthat the hand holding the bottle was as essential as the water inside,so these were substituted by tin foil coatings inside and outside thebottle.Benjamin Franklin, American statesman, scientist and printer, madenumerous experiments with the Leyden jar. He connected severaljars in parallel, as he called it, which gave a discharge strong enoughto kill a turkey. He also connected the jars in series, or " in cascade "as he called it, thus establishing the principle of parallel and seriesconnections. Noticing the similarity between the electric spark andlightning, Franklin in 1752, performed his famous kite experiment.Flying a kite in a thunderstorm, he drew electricity from the cloudsto charge Leyden jars, which were later discharged, proving thatlightning and electricity were the same. This led him to invent thelightning rod.
ELECTRICITY GENERATED BY CHEMICAL MEANSLuigi Galvani was an Italian scientist. About 1785, so the storygoes, his wife was in delicate health, and some frog legs were beingskinned to make her a nourishing soup. An assistant holding the legswith a metal clamp and cutting the skin with a scalpel, happened tolet the clamp and scalpel touch each other. To his amazement thefrog legs twitched. Galvani repeated the experiment many times
4 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 76by touching the nerve with a metal rod and the muscle with a differentmetal rod and allowing the rods to touch, and propounded the theoryof animal electricity in a paper he published in 1791.Allesandro Volta, a professor of physics in the University of Pavia,Italy, read about Galvani's work and repeated his experiments. Hefound that the extent of the movement of the frog legs dependedon the metals used for the rods, and thus believed that the electriccharge was produced by the contact of dissimilar metals with themoisture in the muscles. To prove his point he made a pile of silver
Voltaic Pile, 1799.Volta discovered that electricity could be generated by chemicalmeans and made a pile of silver and zinc discs with cloths, wet withsalt water, between them. This was the forerunner of the present-day dry battery. Photograph courtesy Prof. Chas. F. ChandlerMuseum, Columbia University, New York.and zinc discs with cloths, wet with salt water, between them. Thiswas in 1799, and he described his pile in March, 1800, in a letter tothe Royal Society in London.This was an epoch-making discovery as it was the forerunner of thepresent-day primary battery. Volta soon found that the generationof electricity became weaker as the cloths became dry, so to overcomethis he made his " crown of cups." This consisted of a series ofcups containing salt water in which strips of silver and zinc weredipped. Each strip of silver in one cup was connected to the zincstrip in the next cup, the end strips of silver and zinc being terminalsof the battery. This was the first time that a continuous supply of
NO. 2 HISTORY OF ELECTRIC LIGHT—SCHROEUER 5
electricity in reasonable quantities was made available, so the Volt,the unit of electrical pressure was named in his honor. It was latershown that the chemical affinity of one of the metals in the liquidwas converted into electric energy. The chemical action of Volta'sbattery is that the salt water attacks the zinc when the circuit isclosed forming zinc chloride, caustic soda and hydrogen gas. Thechemical equation is
:
Zn+ 2NaCl + 2U0O = ZnClo + 2NaOH + Hoimprovement of volta's batteryIt was early suggested that sheets of silver and zinc be solderedtogether back to back and that a trough be divided into cells by thesebimetal sheets being put into grooves cut in the sides and bottom of thetrough. This is the reason why one unit of a battery is called a " cell."It was soon found that a more powerful cell could be made if copper,zinc and dilute sulphuric acid were used. The zinc is dissolved bythe acid forming zinc sulphate and hydrogen gas, thus:Zn + H2SO4= ZnS04 + HoThe hydrogen gas appears as bubbles on the copper and reduces theopen circuit voltage (about 0.8 volt per cell) as current is taken fromthe battery. This is called " polarization." Owing to minute im-purities in the zinc, it is attacked by the acid even when no current istaken from the battery, the impurities forming with the zinc a shortcircuited local cell. This is called " local action," and this difficultywas at first overcome by removing the zinc from the acid when thebattery was not in use. Davy's discoveriesSir Humphry Davy was a well-known English chemist, and withthe aid of powerful batteries constructed for the Royal Institution inLondon, he made numerous experiments on the chemical efifects ofelectricity. He decomposed a number of substances and discoveredthe elements boron, potassium and sodium. He heated strips ofvarious metals to incandescence by passing current through them,and showed that platinum would stay incandescent for some timewithout oxidizing. This was about 1802.In the early frictional machines, the presence of electricity wasshown by the fact that sparks could be obtained. Similarly the break-ing of the circuit of a battery would give a spark. Davy, about 1809,demonstrated that this spark could be maintained for a long time with
6 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 76
the large battery of 2000 cells he had had constructed. Using twosticks of charcoal connected by wires to the terminals of this verypowerful battery, he demonstrated before the Royal Society the lightproduced by touching the sticks together and then holding them aparthorizontally about three inches. The brilliant flame obtained he calledan " arc " because of its arch shape, the heated gases, rising, assumingthis form. Davy was given the degree of LL. D. for his dis-tinguished research work, and was knighted on the eve of his mar-riage, April II, 18 12.RESEARCHES OF OERSTED, AMPERE, SCHWEIGGER AND STURGEONHans Christian Oersted was a professor of physics at the Uni-versity of Copenhagen in Denmark. One day in 1819, while ad-dressing his students, he happened to hold a wire, through whichcurrent was flowing, over a large compass. To his surprise he sawthe compass was deflected from its true position. He promptly madea number of experiments and discovered that by reversing the currentthe compass was deflected in the opposite direction. Oersted an-nounced his discovery in 1820.Andre Marie Ampere was a professor of mathematics in the EcolePolytechnic in Paris. Hearing of Oersted's discovery, he immedi-ately made some experiments and made the further discovery in 1820that if the wire is coiled and current passed through it, the coil hadall the properties of a magnet.These two discoveries led to the invention of Schweigger in 1820,of the galvanometer (or " multiplier" as it was then called), a verysensitive instrument for measuring electric currents. It consisted ofa delicate compass needle suspended in a coil of many turns of wire.Current in the coil deflected the needle, the direction and amount ofdeflection indicating the direction and strength of the current.Ampere further made the discovery that currents in opposite direc-tions repel and in the same directions attract each other. He also gavea rule for determining the direction of the current by the deflection ofthe compass needle. He developed the theory that magnetism iscaused by electricity flowing around the circumference of the bodymagnetised. The Ampere, the unit of flow of electric current, wasnamed in honor of his discoveries.In 1825 it was shown by Sturgeon that if a bar of iron were placedin the coil, its magnetic strength would be very greatly increased,which he called an electro-magnet.
no. 2 history of electric light schroeder 7ohm's lawGeorg Simon Ohm was born in Bavaria, the oldest son of a poorblacksmith. With the aid of friends he went to college and becamea teacher. It had been shown that the rate of transfer of heat fromone end to the other of a metal bar is proportional to the difference oftemperature between the ends. About 1825, Ohm, by analogy andexperiment, found that the current in a conductor is proportionalto the difference of electric pressure (voltage) between its ends.He further showed that with a given difference of voltage, the currentin different conductors is inversely proportional to the resistance ofthe conductor. Ohm therefore propounded the law that the currentflowing in a circuit is equal to the voltage on that circuit divided bythe resistance of the circuit. In honor of this discovery, the unit ofelectrical resistance is called the Ohm. This law is usually ex-pressed as
:
"C" meaning current (in amperes), "E" meaning electromotiveforce or voltage (in volts) and "R" meaning resistance (in ohms).This is one of the fundamental laws of electricity and if thoroughlyunderstood, will solve many electrical problems. Thus, if any two ofthe above units are known, the third can be determined. Examples
:
An incandescent lamp on a 120-volt circuit consumes 0.4 ampere,hence its resistance under such conditions is 300 ohms. Severaltrolley cars at the end of a line take 100 amperes to run them and theresistance of the overhead wire from the power house to the trolleycars is half an ohm ; the drop in voltage on the line between the powerhouse and trolley cars is therefore 50 volts, so that if the voltage atthe power house were 600, it would be 550 volts at the end of the line.Critics derided Ohm's law so that he was forced out of his positionas teacher in the High School in Cologne. Finally after ten yearsOhm began to find supporters and in 1841 his law was publiclyrecognized by the Royal Society of London which presented him withthe Copley medal. INVENTION OF THE DYNAMOMichael Faraday was an English scientist. Born of parents inpoor circumstances, he became a bookbinder and studied books onelectricity and chemistry. He finally obtained a position as laboratoryassistant to Sir Humphry Davy helping him with his lectures and
8 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 76
experiments. He also made a number of experiments himself and suc-ceeded in liquifying chlorine gas for which he was elected to a Fel-lowship in the Royal Institution in 1824. Following up Oersted'sand Ampere's work, he endeavored to find the relation betweenelectricity and magnetism. Finally on Oct. 17, 1831, he made theexperiment of moving a permanent bar magnet in and out of a coilof wire connected to a galvanometer. This generated electricity inthe coil which deflected the galvanometer needle. A few days after,Oct. 28, 1831, he mounted a copper disk on a shaft so that the diskcould be rotated between the poles of a permanent horseshoe magnet.
Faraday's Dynamo, 1831.Faraday discovered that electricity could be generated by means of apermanent magnet. This principle is used in all dynamos.The shaft and edge of the disk were connected by brushes and wiresto a galvanometer, the needle of which was deflected as the disk wasrotated. A paper on his invention was read before the Royal Societyon November 24, 1831, which appeared in printed form in January,1832.Faraday did not develop his invention any further, being satisfied,as in all his work, in pure research. His was a notable invention butit remained for others to make it practicable. Hippolyte Pixii, aFrenchman, made a dynamo in 1832 consisting of a permanent horse-shoe magnet which could be rotated between two wire bobbinsmounted on a soft iron core. The wires from the bobbins were con-
NO. 2 HISTORY OF ELECTRIC LIGHT—SCHROEDER
nectecl to a pair of brushes touching a commutator mounted on theshaft holding the magnet, and other brushes carried the current fromthe commutator so that the alternating current generated was rectifiedinto direct current.E. M. Clarke, an Englishman made, in 1834, another dynamo inwhich the bobbins rotated alongside of the poles of a permanent
Pixu's Dyna:mo, 1832.Pixii made an improvement by rotating a permanent magnet in theneighborhood of coils of wire mounted on a soft iron core. A com-mutator rectified the alternating current generated into direct cur-rent. This dynamo is in the collection of the Smithsonian Institution.horseshoe magnet. He also made a commutator so that the machineproduced direct current. None of these machines gave more thanfeeble current at low pressure. The large primary batteries that hadbeen made were much more powerful, although expensive to operate.It has been estimated that the cost of current from the 2000-cellbattery to operate the demonstration of the arc light by Davy, wassix dollars a minute. At present retail rates for electricity sold by
10 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 76lighting companies, six dollars would operate Davy's arc light about500 hours or 30,000 times as long.
DANIELl's BATTERY
It was soon discovered that if the zinc electrode were rubbed withmercury (amalgamated), the local action would practically cease,and if the hydrogen bubbles were removed, the operating voltage ofthe cell would be increased. John Frederic Daniell, an Englishchemist, invented a cell in 1836 to overcome these difficulties. His
Daniell's Cell, 1836.Daniell invented a battery consisting of zinc, copper and copper sul-phate. Later the porous cup was dispensed with, which was used tokeep the sulphuric acid formed separate from the solution of coppersulphate, the two liquids then being kept apart by their difference inspecific gravity. It was then called the Gravity Battery and for yearswas used in telegraphy.
cell consisted of a glass jar containing a saturated solution of coppersulphate (CUSO4). A copper cyHnder, open at both ends and per-forated with holes, was put into this solution. On the outside of thecopper cylinder there was a copper ring, located below the surface ofthe solution, acting as a shelf to support crystals of copper sulphate.Inside the cylinder there was a porous earthenware jar containingdilute sulphuric acid and an amalgamated zinc rod. The two liquidswere therefore kept apart but in contact with each other through thepores of the jar. The hydrogen gas given off by the action of the
NO. 2 HISTORY OF ELECTRIC LIGHT SCHROEDER II
sulphuric acid on the zinc, combined with the dissolved copper sul-phate, formed sulphuric acid and metallic copper. The latter wasdeposited on the copper cylinder which acted as the other electrode.Thus the copper sulphate acted as a depolarizer.The chemical reactions in this cell are,In inner porous jar: Zn+ H2S04 = ZnS04+ H2In outer glass jar: H2 + CuS04= H2S04 + CuThis cell had an open circuit voltage of a little over one volt. Laterthe porous cup was dispensed with, the two liquids being kept apart
Grove's Cell, 1838.This consisted of zinc, sulphuric acid, nitric acid and platinum.It made a very powerful battery. The nitric acid is called the depolar-izer as it absorbs the hydrogen gas formed, thus improving the oper-ating voltage.by the difference of their specific gravities. This was known as theGravity cell, and for years was used in telegraphy.
grove's BATTERYSir William Robert Grove, an English Judge and scientist, inventeda cell in 1838 consisting of a platinum electrode in strong nitric acidin a porous earthenware jar. This jar was put in dilute sulphuric acidin a glass jar in which there was an amalgated zinc plate for theother electrode. This had an open circuit voltage of about 1.9 volts.The porous jar was used to prevent the nitric acid from attacking thezinc. The nitric acid was used for the purpose of combining with the
12 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 76hydrogen gas set free by the action of the sulphuric acid on the zinc,and hence was the depolarizing agent. Hydrogen combining withnitric acid forms nitrous peroxide and water. Part of the nitrousperoxide is dissolved in the water, and the rest escapes as fumeswhich, however, are very suffocating.The chemical equations of this cell are as follows:In outer glass jar: Zn + H2S04 = ZnS04 + H2In inner porous jar: H2 + 2HN03= N204 + 2H20An interesting thing about Grove's cell is that it was planned inaccordance with a theory. Grove knew that the electrical energy ofthe zinc-sulphuric acid cell came from the chemical affinity of the tworeagents, and if the hydrogen gas set free could be combined withoxygen (to form water—H2O), such chemical affinity should increasethe strength of the cell. As the hydrogen gas appears at the otherelectrode, the oxidizing agent should surround that electrode. Nitricacid was known at that time as one of the most powerful oxidizingliquids, but as it attacks copper, he used platinum for the other elec-trode. Thus he not only overcame the difficulty of polarization bythe hydrogen gas, but also increased the voltage of the cell by theadded chemical action of the combination of hydrogen and oxygen.
grove's DEMONSTRATION OF INCANDESCENT LIGHTINGIn 1840 Grove made an experimental lamp by attaching the endsof a coil of platinum wire to copper wires, the lower parts of whichwere well varnished for insulation. The platinum wire was coveredby a glass tumbler, the open end set in a glass dish partly filled withwater. This prevented draughts of air from cooling the incandescentplatinum, and the small amount of oxygen of the air in the tumblerreduced the amount of oxidization of the platinum that would other-wise occur. With current supplied by a large number of cells of hisbattery, he lighted the auditorium of the Royal Institution with theselamps during one of the lectures he gave. This lamp gave only afeeble light as there was danger of melting the platinum and platinumgives but little light unless operated close to its melting temperature.It also required a lot of current to operate it as the air tended to coolthe incandescent platinum. The demonstration was only of scientificinterest, the cost of current being much too great (estimated atseveral hundred dollars a kilowatt hour) to make it commercial.
NO. 2 HISTORY OF ELECTRIC LIGHT SCHROEDER 13GRENET BATTERYIt was discovered that chromic anhydride gives up oxygen easierthan nitric acid and consequently if used would give a higher voltagethan Grove's nitric acid battery. It also has the advantage of a lessertendency to attack zinc directly if it happens to come in contact with it.Grenet developed a cell having a liquid consisting of a mixture ofpotassium bichromate (K2Cr207) and sulphuric acid. A porous cellwas therefore not used to keep the two liquids apart.. This had the
Grove's Incandescent Lamp, 1840.Grove made an experimental lamp, using platinum for the burnerwhich was protected from, draughts of air by a glass tumbler.
advantage of reducing the internal resistance. The chemical reactionwas:KoCraOy (potassium bichromate) +7H2SO4 (sulphuric acid) + 3Zn(zinc) =3ZnS04 (zinc sulphate) +K2SO4 (potassium sulphate)+ Cr2 (504)3 (chromium sulphate) +7H2O (water).In order to prevent the useless consumption of zinc on open circuit,the zinc was attached to a sliding rod and could be drawn up into theneck of the bottle-shaped jar containing the liquid.DE MOLEYNS' INCANDESCENT LAMPFrederick De Moleyns, an Englishman, has the honor of havingobtained the first patent on an incandescent lamp. This was in 1841and his lamp was quite novel. It consisted of a spherical glass globe,in the upper part of which was a tube containing powdered charcoal.This tube was open at the bottom inside the globe and through it ran a
14 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. "J^platinum wire, the end below the tube being coiled. Another platinumwire coiled at its upper end came up through the lower part ofthe globe but did not quite touch the other platinum coil. The pow-dered charcoal filled the two coils of platinum wire and bridged thegap between. Current passing through this charcoal bridge heatedit to incandescence. The air in the globe having been removed as faras was possible with the hand air pumps then available, the charcoaldid not immediately burn up, the small amount consumed being re-placed by the supply in the tube. The idea was ingenious but the
De Moleyns' Incandescent Lamp, i{This consisted of two coils of platinum wire containing powderedcharcoal operating in a vacuum. It is only of interest as the firstincandescent lamp on which a patent (British) was granted.lamp was impractical as the globe rapidly blackened from the evapo-ration of the incandescent charcoal.
EARLY DEVELOPMENTS OF THE ARC LAMPIt had been found that most of the hght of the arc came fromthe tip of the positive electrode, and that the charcoal electrodes wererapidly consumed, the positive electrode about twice as fast as thenegative. Mechanisms were designed to take care of this, togetherwith devices to start the arc by allowing the electrodes to touch eachother and then pulling them apart the proper distance. This distancevaried from one-eighth to three-quarters of an inch.
NO. 2 HISTORY OF ELECTRIC LIGHT—SCHROEDER 15
In 1840 Bunsen, the German chemist who invented the bunsenburner, devised a process for making hard dense carbon pencils whichlasted much longer than the charcoal previously used. The densecarbon from the inside of the retorts of gas making plants was groundup and mixed with molasses, moulded into shape and baked at a hightemperature. Bunsen also, in 1843, cheapened Grove's battery bysubstituting a hard carbon plate in place of the platinum electrode.Thomas Wright, an Englishman, was the first to patent an arc lamp.This was in 1845, and the lamp was a hand regulated device consisting
Wright's Arc Lamp, 1845.This lamp is also only of interest as the first arc lamp on which apatent (British) was granted. Four arcs played between the five car-bon discs.
of five carbon disks normally touching each other and rotated by clock-work. Two of the disks could be drawn outward by thumb screws,which was to be done after the current was turned on thus establishingfour arcs, one between each pair of disks. The next year, 1846, W. E.Staite, another Englishman, made an arc lamp having two verticalcarbon pencils. The upper was stationary. The lower was movableand actuated by clockwork directed by ratchets which in turn wereregulated by an electro-magnet controlled by the current flowingthrough the arc. Thus the lower carbon would be moved up or downas required.Archereau, a Frenchman, made a very simple arc lamp in 1848.The upper carbon was fixed and the lower one was mounted on a
i6 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 76
piece of iron which could be drawn down into a coil of wire. Theweight of the lower electrode was overbalanced by a counterweight,so that when no current was flowing the two carbons would touch.When current was turned on, it flowed through the two carbons andthrough the coil of wire (solenoid) which then became energizedand pulled the lower carbon down, thus striking the arc. Two of thesearc lamps were installed in Paris and caused considerable excitement.After a few weeks of unreliable operation, it was found that the costof current from the batteries was much too great to continue their
Archereau's Arc Lamp, i{This simple arc was controlled by an electro-magnet, and two lampswere installed for street lighting in Paris, current being obtained frombatteries.
use commercially. The dynamo had not progressed far enough topermit its use. joule's lawJoule was an Englishman, and in 1842 began investigating therelation between mechanical energy and heat. He first showed that,by allowing a weight to drop from a considerable height and turn apaddle wheel in water, the temperature of the water would increasein relation to the work done in turning the wheel. It is now knownthat 778 foot-pounds (i lb. falling 778 feet, 10 lbs. falling 77.8 feetor 778 lbs. falling one foot, etc.) is the mechanical equivalent ofenergy equal to raising one pound of water one degree Fahrenheit.
NO. 2 HISTORY OF ELECTRIC LIGHT—SCHROEDER 1
7
The rate of energy (power) is the energy divided by a unit of time
;
thus one horsepower is 33,000 foot-pounds per minute. Joule nextinvestigated the relation between heat and electric current. He madea device consisting of a vessel of water in which there were a ther-mometer and an insulated coil of wire having a considerable resistance.He found that an electric current heated the water, and making manycombinations of the amount and length of time of current flowingand of the resistance of the wire, he deduced the law that the energyin an electric circuit is proportional to the square of the amount ofcurrent flowing multiplied by the length of time and multiplied by theresistance of the wire.The rate of electrical energy (electric power) is therefore propor-tional to the square of current multiplied by the resistance. Theelectrical unit of power is now called the Watt, named in honor ofJames Watt, the Englishman, who made great improvements to thesteam engine about a century ago. Thus, watts = C'R and substitutingEthe value of R from Ohm's law, C = ^, we getWatts = Volts X AmperesThe watt is a small unit of electric power, as can be seen from thefact that 746 watts are equal to one horsepower. The kilowatt, kilobeing the Greek word for thousand, is looo watts.This term is an important one in the electrical industry. Forexample, dynamos are rated in kilowatts, expressed as KW ; the largestone made so far is 50,000 KW which is 66,666 horsepower. Edison'sfirst commercial dynamo had a capacity of 6 KW although the termswatts and kilowatts were not in use at that time. The ordinary sizesof incandescent lamps now used in the home are 25, 40 and 50 watts.Starr's incandescent lampJ. W. Starr, an American, of Cincinnati, Ohio, assisted financiallyby Peabody, the philanthropist, went to England where he obtaineda patent in 1845 on the lamps he had invented, although the patent wastaken out under the name of King, his attorney. One is of passinginterest only. It consisted of a strip of platinum, the active length ofwhich could be adjusted to fit the battery strength used, and wascovered by a glass globe to protect it from draughts of air. The other,a carbon lamp, was the first real contribution to the art. It consistedof a rod of carbon operating in the vacuum above a column of mercury(Torrecellium vacuum) as in a barometer. A heavy platinum wire
SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 76
was sealed in the upper closed end of a large glass tube, and connectedto the carbon rod by an iron clamp. The lower end of the carbon rodwas fastened to another iron clamp, the two clamps being held inplace and insulated from each other by a porcelain rod. Attached tothe lower clamp was a long copper wire. Just below the lower clamp,
Starr's Incandescent Lamp, 1845.This consisted of a short carbon pencil operating in the vacuum abovea column of mercury.
the glass tube was narrowed down and had a length of more than30 inches. The tube was then filled with mercury, the bottom of thetube being put into a vessel partly full of mercury. The mercury ranout of the enlarged upper part of the tube, coming to rest in the narrowpart of the tube as in a barometer, so that the carbon rod was then ina vacuum. One lamp terminal was the platinum wire extendingthrough the top of the tube, and the other was the mercury. Several
No. 2 HISTORY OF ELECTRIC LIGHT SCHROEDER 19
of these lamps were put on exhibition in London, but were not a com-mercial success as they blackened very rapidly. Starr started hisreturn trip to the United States the next year, but died on board theship when he was but 25 years old.OTHER EARLY INCANDESCENT LAMPSIn 1848 W. E. Staite, who two years previously had made an arclamp, invented an incandescent lamp. This consisted of a platinum-iridium burner in the shape of an inverted U, covered by a glass globe.
Staite's IncandescentLamp, 1848.The burner was of platinumand iridium.
Roberts' IncandescentLamp, 1852.It had a graphite burner oper-ating in vacuum.
It had a thumb screw for a switch, the whole device being mountedon a bracket which was used for the return wire. E. C. Shepard,another Englishman, obtained a patent two years later on an incan-descent lamp consisting of a weighted hollow charcoal cylinder theend of which pressed against a charcoal cone. Current passingthrough this high resistance contact, heated the charcoal to incandes-cence. It operated in a glass globe from which the air could be ex-hausted. M. J. Roberts obtained an English patent in 1852 on anincandescent lamp. This had a graphite rod for a burner, whichcould be renewed, mounted in a glass globe. The globe was cementedto a metallic cap fastened to a piece of pipe through which the air
20 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 76
could be exhausted. After being exhausted, the pipe, having a stopcock, could be screwed on a stand to support the lamp.Moses G. Farmer, a professor at the Naval Training Station atNewport, Rhode Island, lighted the parlor of his home at 11 PearlStreet, Salem, Mass., during July, 1859, with several incandescentlamps having a strip of platinum for the burner. The novel featureof this lamp was that the platinum strip was narrower at the termi-nals than in the center. Heat is conducted away from the terminalsand by making the burner thin at these points, the greater resistance
Farmer's Incandescent Lamp, 1859.This experimental platinum lamp was made by Professor Farmerand several of them lighted the parlor of his home in Salem,Mass.
of the ends of the burner absorbed more electrical energy thus off-setting the heat being conducted away. This made a more uniformdegree of incandescence throughout the length of the burner, andProf. Farmer obtained a patent on this principle many years later(1882). FURTHER ARC LAMP DEVELOPMENTSDuring the ten years, 1850 to i860, several inventors developedarc lamp mechanisms. Among them was M. J. Roberts, who hadinvented the graphite incandescent lamp. In Roberts' arc lamp,which he patented in 1852, the lower carbon was stationary. Theupper carbon fitted snugly into an iron tube. In the tube was a brasscovered iron rod, which by its weight could push the upper carbon
NO. 2 HISTORY OF ELECTRIC LIGHT—SCHROEDER 21down the tube so the two carbons normally were in contact. Anelectro-magnet in series with the arc was so located that, when ener-gized, it pulled up the iron tube. This magnet also held the brasscovered iron rod from pushing the upper carbon down the tube so thatthe two carbons were pulled apart, striking the arc. When the arcwent out, the iron tube dropped back into its original position, thebrass covered iron rod was released, pushing the upper carbon downthe tube until the two carbons again touched. This closed the circuitagain, striking the arc as before.
Roberts' Arc Lamp,1852.The arc was controlled by anelectro-magnet which held aniron tube to which the uppercarbon was fastened.
Slater and Watson's ArcLamp, 1852.Clutches were used for thefirst time in this arc lamp tofeed the carbons.
In the same year (1852) Slater and Watson obtained an Englishpatent on an arc lamp in which the upper carbon was movable andheld in place by two clutches actuated by electro-magnets. The lowercarbon was fixed, and normally the two carbons touched each other.When current was turned on, the electro-magnet lifted the clutcheswhich gripped the upper carbon, pulling it up and striking the arc.This was the first time that a clutch was used to allow the carbon tofeed as it became consumed.Henry Chapman, in 1855. made an arc in which the upper carbonwas allowed to feed by gravity, but held in place by a chain wound
22 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 1^
around a wheel. On this wheel was a brake actuated by an electro-magnet. The lower carbon was pulled down by an electro-magnetworking against a spring. When no current was flowing or when thearc went out, the two carbons touched. With current on, one electro-magnet set the brake and held the upper carbon stationary. The otherelectro-magnet pulled the lower carbon down, thus striking the arc.None of these mechanisms regulated the length of the arc. It wasnot until 1856 that Joseph Lacassagne and Henry Thiers, Frenchmen,invented the so-called '' differential " method of control, which madethe carbons feed when the arc voltage, and hence length, became toogreat. This principle was used in commercial arc lamps severalyears afterward when they were operated on series circuits, as it hadthe added advantage of preventing the feeding of one arc lamp affect-
DiAGRAM OF " Differential " Method of Control of an Arc Lamp.This principle, invented by Lacassagne and Thiers, was used in allarc lamps when they were commercially introduced on a large scalemore than twenty years later.ing another on the same circuit. This differential control consists inprinciple of two electro-magnets, one in series with, and opposingthe pull of the other which is in shunt with the arc. The series magnetpulls the carbons apart and strikes the arc. As the arc increases inlength, its voltage rises, thereby increasing the current flowing throughthe shunt magnet. This increases the strength of the shunt magnetand, when the arc becomes too long, the strength of the shunt be-comes greater than that of the series magnet, thus making the carbonsfeed.The actual method adopted by Lacassagne and Thiers was differentfrom this, but it had this principle. They used a column of mercuryon which the lower carbon floated. The upper carbon was stationary.The height of the mercury column was regulated by a valve con-
NO. 2 HISTORY OF ELECTRIC LIGHT—SCHROEDER 23
nected with a reservoir of mercury. The pull of the series magnetclosed the valve fixing the height of the column. The pull of theshunt magnet tended to open the valve, and v^hen it overcame thepull of the series magnet it allowed mercury to flow from the reser-voir, raising the height of the column bringing the carbons nearertogether. This reduced the arc voltage and shunt magnet strengthuntil the valve closed again. Thus the carbons were always kept theproper distance apart. In first starting the arc, or if the arc should
Lacassagne and Thiers' Differentially ControlledArc Lamp, 1856.The lower carbon floated on a column of mercury whose height was" differentially " controlled by series and shunt magnets.go out, current would only flow through the shunt magnet, bringingthe two carbons together until they touched. Current would thenflow through the contact of the two carbons and through the seriesmagnet, shutting the valve. There were no means of pulling thecarbons apart to strike the arc. Current flowing through the highresistance of the poor contact of the two carbons, heated their tipsto incandescence. The incandescent tips would begin to burn away,thus after a time starting an arc. The arc, however, once started wasmaintained the proper length.
24 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 76
In 1857, Serrin took out his first patent on an arc lamp, the generalprinciples of which were the same as in others he made. The mechan-ism consisted of two drums, one double the diameter of the other.Both carbons were movable, the upper one feeding down, and thelower one feeding up, being connected with chains wound aroundthe drums. The difference in consumption of the two carbons wastherefore compensated for by the difference in size of the drums,thus maintaining the location of the arc in a fixed position. A train
Serrin's Arc Lamp, 1857.This type of arc was not differentially controlled but was the firstcommercial lamp later used. Both carbons v/ere movable, held bychains wound around drums which were controlled by ratchets actu-ated by an electro-magnet.
of wheels controlled by a pawl and regulated by an electro-magnet,controlled the movement of the carbons. The weight of the uppercarbon and its holder actuates the train of wheels.DEVELOPMENT OF THE DYNAMO, 184O-1860During the first few years after 1840 the dynamo was only a labora-tory experiment. Woolrich devised a machine which had severalpairs of magnets and double the number of coils in order to makethe current obtained less pulsating. Wheatstone in 1845 patentedthe use of electro-magnets in place of permanent magnets. Brett in1848 suggested that the current, generated in the coils, be allowed to
NO. 2 HISTORY OF ELECTRIC LIGHT SCHROEDER 25flow through a coil surrounding each permanent magnet to furtherstrengthen the magnets. Pulvermacher in 1849 proposed the use ofthin plates of iron for the bobbins, to reduce the eddy currents gen-erated in the iron. Sinsteden in 185 1 suggested that the current froma permanent magnet machine be used to excite the field coils of anelectro-magnet machine.In 1855 Soren Hjorth, of Copenhagen, Denmark, patented adynamo having both permanent and electro-magnets, the latter being
Siemens' Dynamo, 1856.This dynamo was an improvement over others on account of theconstruction of its " shuttle " armature.
excited by currents first induced in the bobbins by the permanentmagnets. In 1856 Dr. Werner Siemens invented the shuttle woundarmature. This consisted of a single coil of wire wound lengthwiseand counter sunk in a long cylindrical piece of iron. This revolvedbetween the magnet poles which were shaped to fit the cylindricalarmature.THE FIRST COMMERCIAL INSTALLATION OF AN ELECTRIC LIGHTIn 1862 a Serrin type of arc lamp was installed in the Dungenesslighthouse in England. Current was supplied by a dynamo made by
26 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 'jG
the Alliance Company, which had been originally designed in 1850by Nollet, a professor of Physics in the Military School in Brussels.Nollet's original design was of a dynamo having several rows of per-manent magnets mounted radially on a stationary frame, with anequal number of bobJMns mounted on a shaft which rotated and had acommutator so direct current could be obtained. A company wasformed to sell hydrogen gas for illuminating purposes, the gas to bemade by the decomposition of water with current from this machine.
Alliance Dynamo, 1862.This was the dynamo used in the first commercial installation of anarc hght in the Dungeness Lighthouse, England, 1862.
Nollet died and the company failed, but it was reorganized as theAlliance Company a few years later to exploit the arc lamp.About the only change made in the dynamo was to substitute col-lector rings for the commutator to overcome the difficulties of commu-tation. Alternating current was therefore generated in this firstcommercial machine. It had a capacity for but one arc light, whichprobably consumed less than ten amperes at about 45 volts, hencedelivered in the present terminology not over 450 watts or abouttwo-thirds of a horsepower. As the bobbins of the armature un-doubtedly had a considerable resistance, the machine had an efficiencyof not over 50 per cent and therefore required at least one and aquarter horsepower to drive it.
NO. 2 HISTORY OF ELECTRIC LIGHT-l -SCHROfeDEk 27FURTHER DYNAMO DEVELOPMENTSIn the summer of 1886 Sir Charles Wheatstone constructed a self-excited machine on the principle of using the residual magnetism inthe field poles to set up a feeble current in the armature which,passing through the field coils, gradually strengthened the fields untilthey built up to normal strength. It was later found that this ideahad been thought of by an unknown man, being disclosed by a clausein a provisional 1858 English patent taken out by his agent. Wheat-stone's machine was shown to the Royal Society in London and a
Wheatstone's Self-Excited Dynamo, 1866.This machine was the first self-excited dynamo by use of the residualmagnetism in the field poles.paper on it read before the Society on February 14, 1867. The fieldcoils were shimt wound.Dr. Werner Siemens also made a self-excited machine, havingseries fields, a paper on which was read before the Academy ofSciences in Berlin on January 17, 1867. This paper was forwardedto the Royal Society in London and presented at the same meetingat which Wheatstone's dynamo was described. Wheatstone probablypreceded Siemens in this re-discovery of the principle of self-excita-tion, but both are given the merit of it. However, S. A. Varley onDecember 24, 1866, obtained a provisional English patent on this,which was not published until July, 1867.In 1870 Grarrime, a Frenchman, patented his well-known ringarmature. The idea had been previously thought of by Elias, a
28 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 76
Gramme's Dynamo, 1871.These were commercially used, their main feature being the " ringwound armature.
Gramme's "Ring" Armature.Wire coils, surrounding an iron wire core, were all connectedtogether in an endless ring, each coil being tapped with a wire con-nected to a commutator bar.
NO. 2 HISTORY OF ELECTRIC LIGHT SCHROEDER 29
Hollander, in 1842, and by Pacinnotti, an Italian, as shown by thecrude motors (not dynamos) they had made. Gramme's armatureconsisted of an iron wire core coated with a bituminous compoundin order to reduce the eddy currents. This core was wound withinsulated wire coils, all connected together in series as one singleendless coil. Each coil was tapped with a wire connected to a commu-tator bar. His first machine, having permanent magnets for fields,was submitted to the French Academy of Sciences in 1871. Later
Alteneck's Dynamo with " Drum " Wound Armature, 1872.The armature winding was entirely on the surface of the armaturecore, a principle now used in all dynamos.
machines were made with self-excited field coils, which were used incommercial service. They had, however a high resistance armature,so that their efficiency did not exceed 50 per cent.Von Hefner Alteneck, an engineer with Siemens, invented thedrum wound armature in 1872. The wires of the armature were allon the surface of the armature core, the wires being tapped at frequentpoints for connection with the commutator bars. Thus in the earlyseventies, commercial dynamos were available for use in arc lighting,and a few installations were made in Europe.
3d Smithsonian miscellaneous collections vol. 'j^RUSSIAN INCANDESCENT LAMP INVENTORSIn 1872 Lodyguine, a Russian scientist, made an incandescent lampconsisting of a " V " shaped piece of graphite for a burner, whichoperated in nitrogen gas. He Hghted the Admiralty Dockyard atSt. Petersburg with about two hundred of these lamps. In 1872the Russian Academy of Sciences awarded him a prize of 50,000rubles (a lot of real money at that time) for his invention. A com-pany with a capital of 200,000 rubles (then equal to about $100,000)
Lodyguine's IncandescentLamp, 1872.The burner was made ofgraphite and operated in nitro-gen gas.
Konn's Incandescent Lamp,1875.In this lamp the graphite rodsoperated in a vacuum.
was formed but as the lamp was so expensive to operate and had sucha short life, about twelve hours, the project failed.Kosloff, another Russian, in 1875 patented a graphite in nitrogenincandescent lamp, which had several graphite rods for burners, soarranged that when one failed another was automatically connected.Konn, also a Russian, made a lamp similar to Kosloff's except thatthe graphite rods operated in a vacuum. Bouliguine, another Russian,in 1876 made an incandescent lamp having a long graphite rod, only
NO. 2 HISTORY OF ELECTRIC LIGHT—SCHROEDER 31
the upper part of which was in circuit. As this part burned out, therod was automatically pushed up so that a fresh portion then was incircuit. It operated in a vacuum. None of these lamps was com-mercial as they blackened rapidly and were too expensive to maintain.
Bouliguine's Incandescent Lamp, 1876.A long graphite rod, the upper part of which only was in circuit,operated in vacuum. As this part burned out, the rod was auto-matically shoved up, a fresh portion then being in the circuit.THE JABLOCHKOFF CANDLEPaul Jablochkoff was a Russian army officer and an engineer. Inthe early seventies he came to Paris and developed a novel arc light.This consisted of a pair of carbons held together side by side andinsulated from each other by a mineral known as kaolin which vapo-rized as the carbons were consumed. There was no mechanism, the
32 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 76
arc being started by a thin piece of carbon across the tips of the car-bons. Current burned this bridge, starting the arc. The early carbonswere about five inches long, and the positive carbon was twice asthick as the negative to compensate for the unequal consumption ondirect current. This, however, did not work satisfactorily. Laterthe length of the carbons was increased, the carbon made of equal
Jablochkoff " Candle," 1876.This simple arc consisted of a pair of carbons held together side byside and insulated from each other by kaolin. Several boulevards inParis were lighted with these arc lights. This arc lamp is in thecollection of the Smithsonian Institution.
thickness and burned on alternating current of about eight or nineamperes at about 45 volts. He made an alternating current generatorwhich had a stationary exterior armature with interior revolving fieldpoles. Several " candles," as they were called, were put in one fixtureto permit all night service and an automatic device was developed,located in each fixture, so that shottld one " candle " go otit for anyreason, another was switched into service.In 1876 many of these ''candles" were installed and later severalof the boulevards in Paris were lip;hted with them. This was the
NO. 2 HISTORY OF ELECTRIC LIGHT SCHROEDER 33
first large installation of the arc light, and was the beginning of itscommercial introduction. Henry Wilde made some improvementsin the candle by eliminating the kaolin between the carbons whichgave Jablochkoff's arc its peculiar color. Wilde's arc was started byallowing the ends of the carbons to touch each other, a magnet swing-ing them apart thus striking the arc.
Jablochkoff's Alternating Current Dynamo, 1876.This dynamo had a stationary exterior armature and internal re-volving field poles. Alternating current was used for the Jablochkoff" candle " to overcome the difficulties of unequal consumption of thecarbons on direct current.COMMERCIAL INTRODUCTION OF THE DIFFERENTIALLY CONTROLLEDARC LAMPAbout the same time Lontin, a Frenchman, improved Serrin's arclamp mechanism by the application of series and shunt magnets. Thisis the differential principle which was invented by Lacassagne andThiers in 1855 but which apparently had been forgotten. Severalof these lamps were commercially installed in France beginning with1876. ARC LIGHTING IN THE UNITED STATESAbout 1875 William Wallace of xA.nsonia, Connecticut, made anarc light consisting of two rectangular carbon plates mounted ona wooden frame. The arc played between the two edges of the plates,
34 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL, J^
Wallace-Farmer Arc Lamp, 1875.This " differentially controlled " arc lamp consisted of two slabs ofcarbon between which the arc played. In the original lamp the car-bon slabs were mounted on pieces of wood held in place by bolts,adjustment being made by hitting the upper carbon slab with a ham-mer. This lamp is in the collection of the Smithsonian Institution.%i|i^
Wallace-Farmer Dynamo, 1875.This was the first commercial dynamo used in the United States forarc lighting. This dynamo J^ in the collection of the SmithsonianInstitution.
NO. 2 HISTORY OF ELECTRIC LIGHT SCHROEDER 35
which lasted much longer than rods. When the edges had burnedaway so that the arc then became unduly long, the carbon plates werebrought closer together by hitting them with a hammer. Wallacebecame associated with Moses G. Farmer, and they improved thiscrude arc by fastening the upper carbon plate to a rod which was heldby a clutch controlled by a magnet. This magnet had two coils in one,the inner winding in series with the arc, and outer one in shunt andopposing the series winding. The arc was therefore dififerentiallycontrolled.
Weston's Arc Lamp, 1876.This lamp is in the collection of the Smithsonian Institution.They also developed a series wound direct current dynamo.The armature consisted of a number of bobbins, all connectedtogether in an endless ring. Each bobbin was also connected toa commutator bar. There were two sets of bobbins, commutators andfield poles, the equivalent of two machines in one, which could beconnected either to separate circuits, or together in series on onecircuit. The Wallace-Farmer system was commercially used. Thearc consumed about 20 amperes at about 35 volts, but as the carbonplates cooled the arc, the efficiency was poor. The arc flickered backand forth on the edges of the carbons casting dancing shadows. The
36 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 76
carbons, while lasting about 50 hours, were not uniform in density,so the arc would flare up and cast off soot and sparks.Edward Weston of Newark, New Jersey, also developed an arclighting system. His commercial lamp had carbon rods, one above theother, and the arc was also differentially controlled. An oil dash pot
Brush's Dynamo, 1877.This dynamo was used for many years for commercial arc lighting.
Diagram of Brush Armature.The armature was not a closed circuit. For description of its opera-tion, see text.prevented undue pumping of the carbons. His dynamo had a drum-wound armature, and had several horizontal field coils on each side ofone pair of poles between which the armature revolved. The systemwas designed for about 20 amperes, each arc taking about 35 volts.Charles F. Brush made a very successful arc lighting system in1878. His dynamo was unique in that the armature had eight coils,
NO. 2 HISTORY OF ELECTRIC LIGHT SCIIROEUER 37
one end of each pair of opposite coils being connected together andthe other ends connected to a commntator segment. Thus the arma-ture itself was not a closed circuit. The machine had two pairs ofhorizontal poles between which the coils revolved. One end of theone pair of coils in the most active position was connected, by meansof two of the four brushes, in series with one end of the two pairsof coils in the lesser active position. The latter two pairs of coils
Brush's Arc Lamp, 1877.The carbons were differentially controlled. This lamp was usedfor many years.Institution. This lamp is in the collection of the Smithsonian
were connected in multiple with each other by means of the brushestouching adjacent commutator segments. The outside circuit wasconnected to the other two brushes, one of which was connected tothe other end of the most active pair of coils. The other brush wasconnected to the other end of the two lesser active pairs of coils. Theone pair of coils in the least active position was out of circuit. Thefield coils were connected in series with the outside circuit.Brush's arc lamp was also dififerentially controlled. It was de-signed for about 10 amperes at about 45 volts. The carbons werecopper plated to increase their conductivity. Two pairs of carbonswere used for all-night service, each pair lasting about eight hours.
38 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 76A very simple device was used to automatically switch the arc fromone to the other pair of carbons, when the first pair was consumed.This device consisted of a triangular-shaped piece of iron connectedto the solenoid controlling the arc. There was a groove on each of theouter two corners of this triangle, one groove wider than the other.An iron washer surrounded each upper carbon. The edge of eachwasher rested in a groove. The washer in the narrow groove made acomparatively tight fit about its carbon. The other washer in thewider groove had a loose fit about its carbon. Pins prevented thewasher from falling below given points. Both pairs of carbons
Thomson-Houston Arc Dynamo, 1878.This dynamo was standard for many years. This machine is in thecollection of the Smithsonian Institution.
touched each other at the start. When current was turned on, thesolenoid lifted the triangle, the loose-fitting washer gripped its carbonfirst, so that current then only passed through the other pair of carbonswhich were still touching each other. The further movement of thesolenoid then separated these carbons, the arc starting between them.When this pair of carbons became consumed, they could not feed anymore so that the solenoid would then allow the other pair of carbonsto touch, transferring the arc to that pair.Elihu Thomson and Edwin J. Houston in 1878 made a very success-ful and complete arc light system. Their dynamo was specially
NO. 2 HISTORY OF ELECTRIC LIGHT SCHROEDER 39designed to fit the requirements of the series arc lamp. The Thomson-Houston machine was a bipolar, having an armature consisting ofthree coils, one end of each of the three coils having a common termi-nal, or " Y " connected, as it is called. The other end of each coilwas connected to a commutator segment. The machine was to a greatextent self-regulating, that is the current was inherently constant withfluctuating load, as occurs when the lamps feed or when the numberof lamps burning at one time should change for any reason. Thisregulation was accomplished by what is called " armature reaction,"which is the effect the magnetization of the armature has on the fieldstrength. Close regulation was obtained by a separate electro-magnet.0^miDiagram uf T-li Arc Lighting System.
in series with the circuit, which shifted the brushes as the loadchanged. As there were but three commutator segments, one for eachcoil, excessive sparking was prevented by an air blast.The " T-H " (Thompson-Houston) lamp employed the shunt feedprinciple. The carbons were normally separated, being in most typesdrawn apart by a spring. A high resistance magnet, shunted aroundthe arc, served to draw the carbons together. This occurred onstarting the lamp and thereafter the voltage of the arc was held con-stant by the balance between the spring and the shunt magnet. Asthe carbon burned away the mechanism advanced to a point wherea clutch was tripped, the carbons brought together, and the cycle re-peated. Both the T-H and Brush systems were extensively used instreet lighting, for which they were the standard when the open arcwas superseded by the enclosed.
40 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. yeOTHER AMERICAN ARC LIGHT SYSTEMSBeginning with about 1880, several arc light systems were developed.Among these were the Vanderpoele, Hochausen, Waterhouse, Maxim,
Thomson-Houston ArcLamp, 1878.This is an early model with a singlepair of carbons. Thomson DoubleCarbon Arc Lamp.This later model,having two pairs ofcarbons, was commer-cially used for manyyears. This lamp isin the collection ofthe Smithsonian In-stitution.Schuyler and Wood. The direct current carbon arc is inherently moreefficient than the alternating current lamp, owing to the fact that thecontinuous flow of current in one direction maintains on the positive
NO. 2 HISTORY OF ELECTRIC LIGHT—SCHROEDER 4I
carbon a larger crater at the vaporizing point of carbon. This sourcefurnishes the largest proportion of light, the smaller crater in thenegative carbon much less. With the alternating current arc, thelarge crater is formed first on the upper and then on the lower carbon.On account of the cooling between alternations, the mean temperaturefalls below the vaporizing point of carbon, thus accounting for thelower efBciency of the alternating current arc.For this reason all these systems used direct current and the 10ampere ultimately displaced the 20 ampere system. The 10 ampere
Maxim Dynamo.This dynamo is in the collection of the Smithsonian Institution.
circuit was later standardized at 9.6 amperes, 50 volts per lamp. Thelamp therefore consumed 480 watts giving an efificiency of about 15lumens per watt. This lamp gave an average of 575 candlepower(spherical) in all directions, though it was called the 2000 cp (candle-power) arc as under the best possible conditions it could give thiscandlepower in one direction. Later a 6.6 ampere arc was developed.This was called the " 1200 cp " lamp and was not c^uite as efficient asthe 9.6 ampere lamp.
42 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. '](iSUB-DIVIDING THE ELECTRIC LIGHTWhile the arc lamp was being commercially established, it was atonce seen that it was too large a unit for household use. Many inven-tors attacked the problem of making a smaller unit, or, as it wascalled, " sub-dividing the electric light." In the United States therewere four men prominent in this work : WilHam E. Sawyer, Moses G.Farmer, Hiram S. Maxim and Thomas A. Edison. These men didnot make smaller arc lamps but all attempted to make an incandescentlamp that would operate on the arc circuits.
Sawyer's IncandescentLamp, 1878.This had a graphite burneroperating in nitrogen gas.
Farmer's IncandescentLamp, 1878.The graphite burner oper-ated in nitrogen gas. Thislamp is in the collection of theSmithsonian Institution.Sawyer made several lamps in the years 1878-79 along the lines ofthe Russian scientists. All his lamps had a thick carbon burneroperating in nitrogen gas. They had a long glass tube closed at oneend and the other cemented to a brass base through which the gaswas put in. Heavy fluted wires connected the burner with the baseto radiate the heat, in order to keep the joint in the base cool. Theburner was renewable by opening the cemented joint. Farmer's lampconsisted of a pair of heavy copper rods mounted on a rubber cork,between which a graphite rod was mounted. This was inserted ina glass bulb and operated in nitrogen gas. Maxim made a lamphaving a carbon burner operating in a rarefied hydrocarbon vapor.He also made a lamp consisting of a sheet of platinum operating in air.
NO. 2 HISTORY OF ELECTRIC LIGHT SCHROEDER 43EDJSON S INVENTION OF A PRACTICAL INCANDESCENT LAMPEdison began the study of the problem in the spring of 1878. Hehad a well-equipped laboratory at ]\Ienlo Park, New Jersey, withseveral able assistants and a number of workmen, about a hundredpeople all told. He had made a number of well-known inventions,among which were the quadruplex telegraph whereby four messagescould be sent simultaneously over one wire, the carbon telephonetransmitter without which Bell's telephone receiver would have been
Maxim's Incandescent Lamp, 1878.The carbon burner operated in a rarefied hydrocarbon vapor,lamp is in the collection of the Smithsonian Institution. Thisimpracticable, and the phonograph. All of these are in use today, soEdison was eminently fitted to attack the problem.Edison's first experiments were to confirm the failures of otherexperimenters. Convinced of the seeming impossibility of carbon,he turned his attention to platinum as a light giving element. Realiz-ing the importance of operating platinum close to its melting tempera-ture, he designed a lamp which had a thermostatic arrangement sothat the burner would be automatically short circuited the moment itstemperature became dangerously close to melting. The burner con-sisted of a double helix of platinum wire within which was a rod.
44 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 76When the temperature of the platinum became too high, the rod inexpanding would short circuit the platinum. The platinum cooledat once, the rod contracted opening the short circuit and allowingcurrent to flow through the burner again. His first incandescent lamppatent covered this lamp. His next patent covered a similar lamp withan improved thermostat consisting of an expanding diaphragm. Bothof these lamps were designed for use on series circuits.The only system of distributing electricity, known at that time,
Edison's First Experimental Lamp, 1878.The burner was a coil of platinum wire which was protected fromoperating at too high a temperature by a thermostat.
was the series system. In this system current generated in the dynamoarmature flowed through the field coils, out to one lamp after anotherover a wire, and then back to the dynamo. There were no meansby which one lamp could be turned on and ofif without doing the samewith all the others on the circuit. Edison realized that while this wassatisfactory for street lighting where arcs were generally used, it neverwould be commercial for household lighting. He therefore decidedthat a practical incandescent electric lighting system must be patternedafter gas lighting with which it would compete. He therefore made
NO. 2 HISTORY OF ELECTRIC LIGHT SCHROEDER 45
an intensive study of gas distribution and reasoned that a constantpressure electrical system could be made similar to that of gas.The first problem was therefore to design a dynamo that wouldgive a constant pressure instead of constant current. He thereforereasoned that the internal resistance of the armature must be verylow or the voltage would fall as current was taken from the dynamo.Scientists had shown that the most economical use of electricity from
Constant Current DLjnamoo—o—
o
o—o—Diagram of Constant Current Serif.s System.This, in 1878. was the only method of distribnting electric current.
i^^Consfan-l- Voltaqe Dynanrxja^o ^ ^ ^ ^^r^Diagram of Edison's Multiple System, 1879.Edison invented the multiple system of distributing electric current,now universally used.
a primary battery was where the external resistance of the load wasthe same as the internal resistance of the battery, or in other words,50 per cent was the maximum possible efficiency.When Edison proposed a very low resistance armature so that thedynamo would have an efficiency of 90 per cent at full load, he wasridiculed. Nevertheless he went ahead and made one which attainedthis. The armature consisted of drum-wound insulated copper rods,the armature core having circular sheets of iron with paper betweento reduce the eddy currents. There were two vertical fields above and
46 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 76
connected in shunt with the armature. It generated electricity at abouta hundred volts constant pressure and could supply current up to about60 amperes at this pressure. It therefore had a capacity, in thepresent terminology, of about 6 kilowatts (or 8 horsepower).A multiple system of distribution would make each lamp indepen-dent of every other and with a dynamo made for such a system, thenext thing was to design a lamp for it. Having a pressure of about
Edison Dynamo, 1879.Edison made a dynamo that was 90 per cent efficient which scientistssaid was impossible. This dynamo is in the collection of the Smith-sonian Institution and was one of the machines on the steamshipColumbia, the first commercial installation of the Edison lamp.
a hundred volts to contend with, the lamp, in order to take a smallamount of current, must, to comply with Ohm's law, have a highresistance. He therefore wound many feet of fine platinum wire ona spool of pipe clay and made his first high resistance lamp. He usedhis diaphragm thermostat to protect the platinum from melting, and,as now seems obvious but was not to all so-called electricians at thattime, the thermostat was arranged to open circuit instead of shortcircuit the burner when it became too hot. This lamp apparentlysolved the problem, and, in order to protect the platinum from the
NO. 2 HISTORY OF ELECTRIC LIGHT SCHROEDER .47
oxygen of the air, he coated it with oxide of zirconium. Unfortu-nately zirconia, while an insulator at ordinary temperatures, becomes,as is now known, a conductor of electricity when heated, so that thelamp short circuited itself when it was lighted.
Edison's High ResistancePlatinum Lamp, 1879.This lamp had a high resis-tance burner, necessary for themultiple system.
Edison's High ResistancePlatinum in VacuumLamp, 1879.This experimental lamp ledto the invention of the success-ful carbon filament lamp.
During his experiments he had found that platinum became ex-ceedingly hard after it had been heated several times to incandescenceby current flowing through it. This apparently raised its meltingtemperature so he was able to increase the operating temperatureand therefore greatly increase the candlepower of his lamps after
48 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 76they had been heated a few times. Examination of the platinumunder a microscope showed it to be much less porous after heating,SO he reasoned that gases were occluded throughout the platinumand were driven out by the heat. This led him to make a lamp witha platinum wire to operate in vacuum, as he thought that more of theoccluded gases would come out under such circumstances.These lamps were expensive to make, and, knowing that he couldget the requisite high resistance at much less cost from a long and
Edison's Carbon Lamp of October 21, 1879.This experimental lamp, having a high resistance carbon filamentoperating in a high vacuum maintained by an all-glass globe, wasthe keystone of Edison's successful incandescent lighting system. Allincandescent lamps made today embody the basic features of thislamp. This replica is in the Smithsonian Institution exhibit of Edisonlamps. The original was destroyed.
slender piece of carbon, he thought he might be able to make the carbonlast in the high vacuum he had been able to obtain from the newlyinvented Geissler and Sprengel mercury air pumps. After severaltrials he finally was able to carbonize a piece of ordinary sewing thread.This he mounted in a one-piece all glass globe, all joints fused by melt-ing the glass together, which he considered was essential in order tomaintain the high vacuum. Platinum wires were fused in the glass toconnect the carbonized thread inside the bulb with the circuit outsideas platinum has the same coefficient of expansion as glass and hencemaintains an airtight joint. He reasoned that there would be oc-cluded gases in the carbonized thread which would immediately burn
NO. 2 HISTORY OF ELECTRIC LIGHT SCHROEDER 49
up if the slightest trace of oxygen were present, so he heated thelamp while it was still on the exhaust pump after a high degree ofvacuum had been obtained. This was accomplished by passing asmall amount of current through the " filament," as he called it, gentlyheating it. Immediately the gases started coming out, and it took eighthours more on the pump before they stopped. The lamp was thensealed and ready for trial.On October 21, 1879, current was turned into the lamp and itlasted forty-five hours before it failed. A patent was applied for
Demonstration of Edison's Incandescent Lighting System.Showing view of Menlo Park Laboratory Buildings, 1880.
on November 4th of that year and granted January 27, 1880. Allincandescent lamps made today embody the basic features of thislamp. Edison immediately began a searching investigation of the bestmaterial for a filament and soon found that carbonized paper gaveseveral hundred hours life. This made it commercially possible, soin December, 1879. it was decided that a public demonstration of hisincandescent lighting system should be made. Wires were run toseveral houses in IMenlo Park, N. J., and lamps were also mounted onpoles, lighting the country roads in the neighborhood. An articleappeared in the New York Herald on Sunday, December 21, 1879,describing Edison's invention and telling of the public demonstrationto be given during the Christmas holidays. This occupied the entirefirst page of the paper, and created such a furor that the PennsylvaniaRailroad had to run special trains to Menlo Park to accommodate
so SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 76
the crowds. The first commercially successful installation of theEdison incandescent lamps and lighting system was made on thesteamship Columbia, which started May 2, 1880, on a voyage aroundCape Horn to San Francisco, Calif.The carbonized paper filament of the first commercial incandescentlamp was quite fragile. Early in 1880 carbonized bamboo was foundto be not only sturdy but made an even better filament than paper.The shape of the bulb was also changed from round to pear shape,
Dynamo Room, S. S. Columbia.The first commercial installation of the Edison Lamp, startedMay 2, 1880. One of these original dynamos is on exhibit at theSmithsonian Institution.
being blown from one inch tubing. Later the bulbs were blowndirectly from molten glass.As it was inconvenient to connect the wires to the binding posts ofa new lamp every time a burned out lamp had to be replaced, a baseand socket for it were developed. The earliest form of base con-sisted simply of bending the two wires of the lamp back on the neckof the bulb and holding them in place by wrapping string aroundthe neck. The socket consisted of two pieces of sheet copper in ahollow piece of wood. The lamp was inserted in this, the two-wireterminals of the lamp making contact with the two-sheet copperterminals of the socket, the lamp being rigidly held in the socket by
NO. 2 HISTORY OF ELECTRIC LIGHT SCHROEDER 51
a thumb screw which forced the socket terminals tight against theneck of the bulb.This crude arrangement was changed in the latter part of 1880 toa screw shell and a ring for the base terminals, wood being used for
Original Socket i'or Incandi£scent Lamps, i{
Wire Terminal Base Lamp, 1880.This crude form of lamp base fitted the original form of lampsocket pictured above. This lamp is in the exhibit of Edison lampsin the Smithsonian Institution.
insulation. The socket was correspondingly changed. This was avery bulky affair, so the base was changed to a cone-shaped ring anda screw shell for terminals. Wood was used for insulation, whicha short time after was changed to plaster of Paris as this was alsoused to fasten the base to the bulb. It was soon found that the tensioncreated between the two terminals of the base when the lamp was
52 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL, 76firmly screwed in the socket often caused the plaster base to pull apart,SO the shape of the base was again changed early in 1 881, to the formin use today.An improved method of connecting the ends of the filament to theleading-in wires was adopted early in 1881. Formerly this wasaccomplished by a delicate clamp having a bolt and nut. The improve-ment consisted of copper plating the filament to the leading-in wire.In the early part of the year 1881 the lamps were made " eight to
^b
Original Screw BaseLamp, 1880.This first screw base, con-sisting of a screw shell andring for terminals with woodfor insulation, was a verybulky affair. This lamp is inthe exhibit of Edison lamps inthe Smithsonian Institution.
Improved Screw BaseLamp, 1881.The terminals of this baseconsisted of a cone shaped ringand a screw shell. At firstwood was used for insulation,later plaster of paris whichwas also used to fasten thebase to the bulb. This lampis in the exhibit of Edisonlamps in the Smithsonian In-stitution.
the horsepower." Each lamp, therefore, consumed a little less than100 watts, and was designed to give 16 candlepower in a horizontaldirection. The average candlepower (spherical) in all directions wasabout 'jy per cent of this, hence as the modern term " lumen" is 12.57spherical candlepower, these lamps had an initial efficiency of about1.7 lumens per watt. The lamps blackened considerably during theirlife so that just before they burned out their candlepower was lessthan half that when new. Thus their mean efficiency throughout lifewas about i.i 1-p-w (lumens per watt). These figures are interesting
NO. 2 HISTORY OF ELECTRIC LIGHT SCHROEDER 53in comparison with the modern lOO-watt gas-filled tungsten-filamentlamp which has an initial efficiency of 12.9, and a mean efficiency ofII.8, 1-p-w. In other words the equivalent (wattage) size of modernlamp gives over seven times when new, and eleven times on theaverage, as much light for the same energy consumption as Edison'sfirst commercial lamp. In the latter part of 1881 the efficiency waschanged to " ten lamps per horsepower," equivalent to 2I 1-p-winitially. Two sizes of lamps were made: 16 cp for use on iio-volt
( )
^j^^^
Final Form of Screw Base, 1881.With plaster of paris, the previous form of base was apt to pullapart when the lamp was firmly screwed into the socket. The formof the base was therefore changed to that shown, which overcamethese difficulties, and which has been used ever since. The lampshown was standard for three years and is in the exhibit of Edisonlamps in the Smithsonian Institution.
circuits and 8 cp for use either direct or 55 volts or two in series on1 10-volt circuits.
EDISOn's THREE-WIRE SYSTEMThe distance at which current can be economically delivered atno volts pressure is limited, as will be seen from a study of Ohm'slaw. The loss of power in the distributing wires is proportional tothe square of the current flowing. If the voltage be doubled, theamount of current is halved, for a given amount of electric powerdelivered, so that the size of the distributing wires can then be reducedto one-quarter for a given loss in them. At that time (1881) it was
54 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 76impossible to make 220-volt lamps, and though they are now available,their use is uneconomical, as their efficiency is much poorer than thatof iio-volt incandescent lamps.Edison invented a distributing system that had tw^o iio-volt circuits,with one wire called the neutral, common to both circuits so that thepressure on the two outside wires was 220 volts. The neutral wirehad only to be large enough to carry the difference between the cur-rents flowing in the two circuits. As the load could be so arrangedthat it would be approximately ec^ual at all times on both circuits,the neutral wire could be relatively small in size. Thus the three-wiresystem resulted in a saving of 60 per cent in copper over the two-wire
Diagram of Edison's Thrke-Wire System, 1This system reduced the cost of copper in the multiple distributingsystem 60 per cent.system or, for the same amount of copper, the distance that currentcould be delivered was more than doubled.DEVELOPMENT OF THE ALTERNATING CURRENT CONSTANTPOTENTIAL SYSTEMThe distance that current can be economically distributed, as hasbeen shown, depends upon the voltage used. If, therefore, currentcould be sent out at a high voltage and the pressure brought down tothat desired at the various points to which it is distributed, such dis-tribution could cover a much greater area. Lucien Gaulard was aFrench inventor and was backed by an Englishman named John D.Gibbs. About 1882 they patented a series alternating-current systemof distribution. They had invented what is now called a transformerwhich consisted of two separate coils of wire mounted on an iron
NO. 2 HISTORY OF ELECTRIC LIGHT SCHROEDER 55
core. AH the primary coils were connected in series, which, whencurrent went through them, induced a current in the secondary coils.Lamps were connected in multiple on each of the secondary coils.An American patent was applied for on the transformer, but wasrefused on the basis that " more current cannot be.taken from it thanis put in." While this is true if the word energy were used, thetransformer can supply a greater current at a lower voltage (or viceversa) than is put in, the ratio being in proportion to the relativenumber of turns in the primary and secondary coils. The transformerwas' treated with ridicule and Gaulard died under distressing cir-cumstances.Gsns+antVoltageAlternating (Current /Dijnamo 7^High Voltage Circuit
VmAooo
pn
'110 Volt Circuits^ OOooDiAGRAM OF Stanley's Alternating Currknt MultipleSystem, 1885.This sA'Stem is now uniYersally used for distributing electric currentlong distances.Information regarding the transformer came to the attention ofWilliam Stanley, an American, in the latter part of 1885. He madean intensive study of the scheme, and developed a transformer in whichthe primary coil was connected in multiple on a constant potentialalternating-current high-voltage system. From the secondary coil alower constant voltage was obtained. An experimental installationwas made at Great liarrington, Mass., in the early part of 1886, thefirst commercial installation being made in Buffalo, New York, inthe latter part of the year. This scheme enabled current to be eco-nomically distributed to much greater distances. The voltage of thehigh-tension circuit has been gradually increased as the art has pro-gressed from about a thousand volts to over two hundred thousandvolts pressure in a recent installation in California, where electricpower is transmitted over two hundred miles.
56 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 76INCANDESCENT LAMP DEVELOPMENTS, 1 884- 1 894In 1884 the ring of plaster around the top of the base was omitted ;in 1886 an improvement w^as made by pasting the filament to theleading-in wires with a carbon paste instead of the electro-platingmethod; and in 1888 the length of the base was increased so that ithad more threads. Several concerns started making incandescentlamps, the filaments being made by carbonizing various substances.
" Parchmentized " thread consisted of ordinary thread passed throughsulphuric acid. " Tamadine " was cellidose in the sheet form, punched
Standard Edison Lamp, 1884.The rin^ of plaster aroundthe neck of previous lamps wasomitted. This lamp is in theexhibit of Edison lamps in theSmithsonian Institution.
Standard Edison Lamp, 1888.The length of the base wasincreased so it had morethreads. This lamp is in theexhibit of Edison lamps in theSmithsonian Institution.
out in the shape of the filament. Squirted cellulose in the form of athread was also used. This was made by dissolving absorbent cottonin zinc chloride, the resulting syrup being squirted through a die intoalcohol which hardened the thread thus formed. This thread waswashed in water, dried in the air and then cut to proper length andcarbonized.The filament was improved by coating it with graphite. Onemethod, adopted about 1888, was to dip it in a hydro-carbon liquidbefore carbonizing. Another, more generally adopted in 1893 was aprocess originally invented by Sawyer, one of the Americans who hadattempted to " sub-divide the electric light " in 1878-79. This process
NO. 2 HISTORY OF ELECTRIC LIGHT SCHROEDER 57
consisted of passing current through a carhonized filament in anatmosphere of hydrocarbon vapor. The hot filament decomposed thevapor, depositing graphite on the filament. The graphite coated fila-ment improved it so it could operate at 3^ lumens per watt (initial efifi-ciency) . Lamps of 20, 24, 32 and 50 candlepower were developed foriio-volt circuits. Lamps in various sizes from 12 to 36 cp were madefor use on storage batteries having various numbers of cells and givinga voltage of from 20 to 40 volts. Miniature lamps of from ^ to 2 cpfor use on dry batteries of from 2^ to 5^ volts, and 3 to 6 cp on
«Standard Edison Lamp, 1894.This lamp had a " treated " cellulose filament, permitting an effi-ciency of 3J^ lumens per watt which has never been exceeded in acarbon lamp. This lamp is in the exhibit of Edison lamps in theSmithsonian Institution.
5^ to 12 volts, were also made. These could also be connected inseries on no volts for festoons. Very small lamps of -i- cp of 2 to4 volts for use in dentistry and surgery were made available. Theseminiature lamps had no bases, wires being used to connect them tothe circuit.Lamps for 220-volt circuits were developed as this voltage wasdesirable for power purposes, electric motors being used, and a fewlamps were needed on such circuits. They are less efficient and moreexpensive than iio-volt lamps, their use being justified howeveronly when it is uneconomical to have a separate iio-volt circuit forlighting. The lamps were made in sizes from 16 to 50 candlepower.
58 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 76
Edison. Thomson-Houston. Westinghouse. Brush-Swan.
Edi-Swan(single contact). Edi-Swan(double contact). United States. Hawkeye.
Ft. Wayne Jenny. Mather or Perkins. Loomis
Schaeffer or National. Indianapolis Jenny. Siemens & Halske.Various Standard Bases in Use, 1892.
NO. 2 HISTORY OF ELECTRIC LIGHT SCHROEDER 59
Thomson-Houston Socket.
i''lW»Cffl3IRSnSMWa«BKaS9!r:«f
Westinghouse Socket.
6o SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL, 76
Electric street railway systems used a voltage in the neighborhoodof 550, and lamps were designed to burn five in series on this voltage.These lamps were different from the standard i lo-volt lamps althoughthey were made for about this voltage. As they were burned in series,the lamps were selected to operate at a definite current instead of ata definite voltage, so that the lamps when burned in series wouldoperate at the proper temperature to give proper life results. Suchlamps would therefore vary considerably in individual volts, andhence would not give good service if burned on iio-volt circuits.The candelabra screw base and socket and the miniature screw baseand socket were later developed. Ornamental candelabra base lamps
Thomson-Houston. Westinghouse.Adapters for Edison Screw Sockets, 1892.Next to the Edison base, the Thomson-Houston and Westinghousebases were the most popular. By use of these adapters, Edison baselamps could be used in T-H and Westinghouse sockets.
were made for use direct on no volts, smaller sizes being operatedin series on this voltage. The former gave about lo cp, the latter invarious sizes from 4 to 8 cp. The miniature screw base lamps werefor low volt lighting.The various manufacturers of lamps in nearly every instance madebases that were very different from one another. No less than four-teen different standard bases and sockets came into commercial use.These were known as, Brush-Swan, Edison, Edi-Swan (double con-tact), Edi-Swan (single contact). Fort Wayne Jenny, Hawkeye,Indianapolis Jenny, Loomis, Mather or Perkins, Schaeffer or Na-tional, Siemens & Halske, Thomson-Houston, United States andWestinghouse. In addition there were later larger sized bases made
NO. 2 HISTORY OF ELECTRIC LIGHT SCHROEDER 6ifor use on series circuits. These were called the Bernstein, Heisler,Large Edison, Municipal Bernstein, Municipal Edison, Thomson-Houston (alternating circuit) and Thomson-Houston (arc circuit).Some of these bases disappeared from use and in 1900 the proportionin the United States was about 70 per cent Edison, 15 per cent West-
i4h :£r
Bernstein. Heisler. Thomson-Houston(alternating current).
Municipal Bernstein.Thomson-Houston Municipal Edison,(arc circuit). Various Series Bases in Use, 1892.The above six bases have been superseded by the " Large Edison,"now called the Mogul Screw base.
inghouse, 10 per cent Thomson-Houston and 5 per cent for all theothers remaining. A campaign was started to standardize the Edisonbase, adapters being sold at cost for the Westinghouse and Thomson-Houston sockets so that Edison base lamps could be used. In a fewyears the desired results were obtained so that now there are no othersockets in the United States but the Edison screw type for standard
62 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 76lighting service. This appHes also to all other countries in the worldexcept England where the bayonet form of base and socket is stillpopular.THE EDISON " MUNICIPAL " STREET LIGHTING SYSTEMThe arc lamp could not practically be made in a unit smaller thanthe so-called "1200 candlepower " (6.6 ampere) or "half" size,which really gave about 350 spherical candlepower. A demand there-
l^msuN " MuNiLirAL " Svstem, 1885.High voltage direct current was generated, several circuits oper-ating in multiple, three ampere lamps burning in series on each circuit.Photograph courtesy of Association of Edison Illuminating Companies.
fore arose for a small street lighting unit, and Edison designed his
" Municipal " street lighting system to fill this requirement. Hisexperience in the making of dynamos enabled him to make a directcurrent bipolar constant potential machine that would deliver 1000volts which later was increased to 1200 volts. They were first madein two sizes having an output of 12 and 30 amperes respectively.Incandescent lamps were made for 3 amperes in several sizes from16 to 50 candlepower. These lamps were burned in series on the1200-volt direct current system. Thus the 12-ampere machine hada capacity for four series circuits, each taking 3 amperes, the series
NO. 2 HISTORY OF ELECTRIC LIGHT SCHROEDER 63
circuits being connected in multiple across the 1200 volts. Thenumber of lamps on each series circuit depended upon their size, asthe voltage of each lamp was different for each size, being about ihvolts per cp.A popular size was the 32-candlepower unit, which thereforerequired about 45 volts and hence at 3 amperes consumed about 135watts. Allowing 5 i)er cent loss in the wires of each circuit, therewas therefore 1140 of the 1200 volts left for the lamps. Henceabout 25 32-candlepower or 50 i6-candlepower lamps could be put oneach series circuit. Different sizes of lamps could also be put on the
Edison Municipal Lamp, 1885.Inside the base was an arrangement by which the lamp was auto-matically short circuited when it burned out.
same circuit, the number depending upon the aggregate voltage of thelamps.A device was put in the base of each lamp to short circuit the lampwhen it burned out so as to prevent all the other lamps on that circuitfrom going out. This device consisted of a piece of wire put insidethe lamp bulb between the two ends of the filament. Connected tothis wire was a very thin wire inside the base which held a piece ofmetal compressed against a s]:)ring. The spring was connected to oneterminal of the base. Should the lamp burn out, current would jumpfrom the filament to the wire in the bulb, and the current then flowedthrough the thin wire to the other terminal of the liase. The thinwire was melted by the current, and the spring pushed the piece ofmetal up short circuiting the terminals of the base. This scheme was
64 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 76
later simplified by omitting the wire, spring, etc., and substituting apiece of metal which was prevented from short circuiting the termi-nals of the base by a thin piece of paper. When the lamp burnedout the entire 1200 volts was impressed across this piece of paper,puncturing it and so short circuiting the base terminals. Should oneor more lamps go out on a circuit, the increase in current above thenormal 3 amperes was prevented by an adjustable resistance, or anextra lot of lamps which could be turned on one at a time, connectedto each circuit and located in the power station under the control ofthe operator. This system disappeared from use with the advent ofthe constant current transformer.THE SHUNT BOX SYSTEM FOR SERIES INCANDESCENT LAMPSSoon after the commercial development of the alternating currentconstant potential system, a scheme was developed to permit the use
'Reactance Coils-M IConsl-antVoltage .Alternating (Corre.ni' yDynamo Ky aKy Hk>Shunt Box System, liLamps were burned in series on a high voltage alternating current,and when a lamp burned out all the current then went through its
'' shunt box," a reactance coil in multiple with each lamp.
of lamps in series on such circuits without the necessity for shortcircuiting a lamp should it burn out. A reactance, called a " shuntbox " and consisting of a coil of wire wound on an iron core, wasconnected across each lamp. The shunt box consumed but littlecurrent while the lamp was burning. Should one lamp go out, theentire current would flow through its shunt box and so maintain thecurrent approximately constant. It had the difficulty, however, thatif several lamps went out, the current would be materially increasedtending to burn out the remaining lamps on the circuit. This systemalso disappeared from use with the development of the constantcurrent trans fonner.
NO. 2 HISTORY OF ELECTRIC LIGHT SCHROEDER 65THE ENCLOSED ARC LAMPUp to 1893 the carbons of an arc lamp operated in the open air,so that they were rapidly consumed, lasting from eight to sixteenhours depending on their length and thickness. Louis B. Marks, anAmerican, found that by placing a tight fitting globe about the arc,the life of the carbons was increased ten to twelve times. This wasdue to the restricted amount of oxygen of the air in the presence ofthe hot carbon tips and thus retarded their consumption. The amountof light was somewhat decreased, but this was more than offset by
'f
Enclosed Arc Lamp, 1893.Enclosing the arc lengthened the life of the carbons, thereby greatlyreducing the cost of maintenance.
the lesser expense of trimming which also justified the use of moreexpensive better quality carbons. Satisfactory operation requiredthat the arc voltage be increased to about 80 volts.This lamp rapidly displaced the series open arc. An enclosed arclamp for use on i lo-volt constant potential circuits was also developed.A resistance was put in series with the arc for use on iio-volt directcurrent circuits, to act as a ballast in order to prevent the arc fromtaking too much current and also to use up the difference between the
66 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 76
arc voltage (80) and the line voltage (no). On alternating cur-rent, a reactance was used in place of the resistance.The efficiencies in lumens per watt of these arcs (with clear glass-ware), all of which have now disappeared from the market, wereabout as follows
:
6.6 ampere 510 watt direct current (D. C.) series arc, 8^ 1-p-w.5.0 ampere 550 watt direct current multiple (no-volt) arc, 4^ 1-p-w.7.5 ampere 540 watt alternating current (A. C.) multiple (no-volt)arc, 4I 1-p-w.
Opex Flamk ArcLamp, 1898.Certain salts impregnated inthe carbons produced a bril-liantly luminous flame in thearc stream which enormouslyincreased the efficiency of thelamp.
Enclosed Im.a.me ArcLamp, 1908.By condensing the smokefrom the arc in a coolingchamber it was practical to en-close the flame arc, therebyincreasing the life of thecarbons.The reason for the big difference in efficiency between the seriesand multiple direct-current arc is that in the latter a large amount ofelectrical energy (watts) is lost in the ballast resistance. While thereis a considerable difference between the inherent efficiencies of theD. C. and A. C. arcs themselves, this difference is reduced in the
NO. 2 HISTORY OF ELECTRIC LIGHT—SCHROEDER 6^
multiple D. C. and A. C. arc lamps as more watts are lost in theresistance ballast of the multiple D. C. lamp than are lost in thereactance ballast of the multiple A. C. lamp.This reactance gives the A. C. lamp what is called a " power-factor."The product of the amperes (7.5) times the volts (no) does not givethe true wattage (540) of the lamp, so that the actual volt-amperes(825) has to be multiplied by a power factor, in this case about 65 percent, to obtain the actual power (watts) consumed. The reason isthat the instantaneous varying values of the alternating current andpressure, if multiplied and averaged throughout the complete alter-nating cycle, do not equal the average amperes (measured by anammeter) multiplied by the average voltage (measured by a volt-meter). That is, the maximum value of the current flowing (am-peres) does not occur at the same instant that the maximum pressure(voltage) is on the circuit.THE FLAME ARC LAMPAbout 1844 Bunsen investigated the effect of introducing variouschemicals in the carbon arc. Wothing was done, however, untilBremer, a German, experimented with various salts impregnated inthe carbon electrodes. In 1898 he produced the so-called flame arc,which consisted of carbons impregnated with calcium fluoride. Thisgave a brilliant yellow light most of which came from the arc flame,and practically none from the carbon tips. The arc operated in theopen air and produced smoke which condensed into a white powder.The two carbons were inclined downward at about a 30-degreeangle with each other, and were of small diameter but long, 18 to30 inches, having a life of about 12 to 15 hours. The tips of thecarbons projected through an inverted earthenware cup, called the
" economizer," the white powder condensing on this and acting notonly as an excellent reflector but making a dead air space above thearc. The arc was maintained at the tips of the carbons by an electro-magnet whose magnetic field " blew " the arc down.Two flame arc lamps were burned in series on no-volt circuits.They consumed 550 watts each, giving an efficiency of about 35 lumensper watt on direct current. On alternating current the efficiency wasabout 30 1-p-w. By use of barium salts impregnated in the carbons,a white light was obtained, giving an efficiency of about 18 1-p-w ondirect current and about 15-0 on alternating current. These figurescover lamps equipped with clear glassware. Using strontium saltsin the carbons, a red light was obtained at a considerablv lower effi-
68 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 76
ciency, such arcs on account of their color being used only to a limitedextent for advertising purposes.These arcs were remarkably efficient but their maintenance expensewas high. Later, about 1908, enclosed flame arcs with vertical carbons
Constant Current Transformer, 1900.This converted alternating current of constant voltage into constantcurrent, for use on series circuits.
were made which increased the life of the carbons, the smoke beingcondensed in cooling chambers. However, their maintenance expensewas still high. They have now disappeared from the market, havingbeen displaced by the very efficient gas-filled tungsten filament incan-descent lamp which appeared in 19 13.
NO. 2 HISTORY OF ELECTRIC LIGHT SCHROEDER 69THE CONSTANT CURRENT TRANSFORMER FOR SERIES CIRCUITSAbout 1900 the constant current transformer was developed byEHhu Thomson. This transforms current taken from a constantpotential alternating current circuit into a constant alternating currentfor series circuits, whose voltage varies with the load on the circuit.The transformer has two separate coils ; the primary being stationaryand connected to the constant potential circuit and the secondarybeing movable and connected to the series circuit. The weight of thesecondary coil is slightly underbalanced by a counter weight. Currentflowing in the primary induces current in the secondary, the twocoils repelling each other. The strength of the repelling force dependsupon the amount of current flowing in the two coils. The core of thetransformer is so designed that the central part, which the two coilss'lrround, is magnetically more powerful close to the prim.ary coilthan it is further away.When the two coils are close together a higher voltage is inducedin the secondary than if the later were further away from the primarycoil. In starting, the two coils are pulled apart by hand to prevent toolarge a current flowing in the series circuit. The secondary coil isallowed to gradually fall and will come to rest at a point where thevoltage induced in it produces the normal current in the series circuit,the repelling force betwen the two coils holding the secondary at thispoint. Should the load in the series circuit change for any reason, thecurrent in the series circuit would also change, thus changing theforce repelling the two coils. The secondary would therefore moveuntil the current in the series circuit again becomes normal. Theaction is therefore automatic, and the actual current in the seriescircuit can be adjusted within limits to the desired amount, by varyingthe counterweight. A dash pot is used to prevent the secondary coilfrom oscillating (pumping) too much.In the constant current transformer, the series circuit is insulatedfrom the constant potential circuit. This has many advantages. Asimilar device, called an automatic regulating reactance was developedwhich is slightly less expensive, but it does not have the advantage ofinsulating the two circuits from each other.ENCLOSED SERIES ALTERNATING CURRENT ARC LAMPSThe simplicity of the constant current transformer soon drove theconstant direct-current dynamo from the market. An enclosed arclamp was therefore developed for use on alternating constant current.
70 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 76Two sizes of lamps were made ; one for 6.6 amperes consuming 450watts and having an efficiency of about 4^ lumens per watt, and theother 7.5 amperes, 480 watts and 5 1-p-w (clear glassware). Theselamps soon superseded the direct current series arcs. They have nowbeen superseded by the more efficient magnetite arc and tungstenfilament incandescent lamps.
SERIES INCANDESCENT LAMPS ON CONSTANT CURRENT TRANSFORMERSSeries incandescent lamps were made for use on constant currenttransformers superseding the " Alunicipal " and "Shunt Box" sys-tems. The large Edison, now called the Mogul Screw base, wasadopted and the short circuiting film cut-out was removed from thebase and placed between prongs attached to the socket.
Holder. Socket. Holder and socket.Series Incandescent Lamp Socket with Film Cutout, 1900.The " Large Edison," now called Mogul Screw, base was standardizedand the short circuiting device put on the socket terminals.The transformers made for the two sizes of arc lamps, produced6.6 and 7.5 amperes and incandescent lamps, in various sizes from16 to 50 cp, were made for these currents so that the incandescentlamps could be operated on the same circuit with the arc lamps. Thecarbon series incandescent lamp, however, was more efficient if madefor lower currents, so 3^-, 4- and 5|-ampere constant current trans-formers were made for incandescent lamps designed for these am-peres. Later, however, with the advent of the tungsten filament, the6.6-ampere series tungsten lamp was made the standard, as it wasslightly more efficient than the lower current lamps, and was madein sizes from 32 to 400 cp. When the more efficient gas-filledtungsten lamps were developed, the sizes were further increased
;
the standard 6.6-ampere lamps now made are from 60 to 2500 cp.
NO. 2 HISTORY OF ELECTRIC LIGHT SCTIROEDER 71THE NERNST LAMPDr. Walther Nernst, of Germany, investigating the rare earths usedin the Welsbach mantle, developed an electric lamp having a burner,or " glower " as it was called, consisting of a mixture of these oxides.
Nernst Lamp, 1900.The burners consisted mainly of zirconium oxide which had to beheated before current could go through them.
I'he main ingredient was zirconia, and the glower operated in the openair. It is a non-conductor when cold, so had to be heated before cur-rent would flow through it. This was accomplished by an electricheating coil, made of platinum wire, located just above the glower.As the glower became heated and current flowed through it, the heaterwas automatically disconnected by an electro-magnet cut-out.The resistance of the glower decreases with increase in current,so a steadying resistance was put in series with it. This consisted of
72 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 76
an iron wire mounted in a bulb filled with hydrogen gas and was calleda " ballast." Iron has the property of increasing in resistance withincrease in current flowing through it, this increase being very markedbetween certain temperatures at which the ballast was operated. Thelamp was put on the American market in 1900 for use on 220-voltalternating current circuits. The glower consumed 0.4 ampere.One, two, three, four and six glower lamps were made, consuming88, 196, 274, 392 and 528 watts respectively. As most of the lightis thrown downward, their light output was generally given in meanlower hemispherical candlepower. The multiple glower lamps were
Diagram of Nernst Lamp.
more efficient than the single glower, owing to the heat radiated fromone glower to another. Their efficiencies, depending on the size, werefrom about 3^ to 5 lumens per watt, and their average candlepowerthroughout life was about 80 per cent of initial. The lamp disap-peared from the market about 191 2.THE COOPER-HEWITT LAMPIn i860 Way discovered that if an electric circuit was openedbetween mercury contacts a brilliant greenish colored arc was pro-duced. Mercury was an expensive metal and as the carbon arc seemedto give the most desirable results, nothing further was done for manyyears until Dr. Peter Cooper Hewitt, an American, began experiment-
NO. 2 HISTORY OF ELECTRIC LIGHT SCHROEDER 73ing with it. He finally produced an arc in vacuum in a one-inch glasstube about 50 inches long for no volts direct current circuits, whichwas commercialized in 190 1. The tube hangs at about 15 degrees fromthe horizontal. The lower end contains a small quantity of mercury.The terminals are at each end of the tube, and the arc was first startedby tilting the tube by hand so that a thin stream of mercury bridgedthe two terminals. Current immediately vaporized the mercury,starting the arc. A resistance is put in series with the arc to maintainthe current constant on direct current constant vohage circuits.Automatic starting devices were later developed, one of which con-sisted of an electro-magnet that tilted the lamp, and the other of aninduction coil giving a high voltage which, in discharging, started thearc.
Cooper-Hew ITT [Mercury Vapor Arc Lamp, 1901.This gives a very efficient light, practically devoid of red but of highactinic vakie, so useful in photography.
This lamp is particularly useful in photography on account of thehigh actinic value of its light. Its light is very diffused and is practi-cally devoid of red rays, so that red objects appear black in its light.The lamp consumes 3^ amperes at no volts direct current (385watts) having an efficiency of about 12^ lumens per watt.The mercury arc is peculiar in that it acts as an electric valvetending to let current flow through it only in one direction. Thus onalternating current, the current impulses will readily go through itin one direction, but the arc will go out in the other half cycle unlessmeans are taken to prevent this. This is accomplished by having twoterminals at one end of the tube, which are connected to choke coils,which in turn are connected to a single coil (auto) transformer. Thealternating current supply mains are connected to wires tapping dif-ferent parts of the coil of the auto transformer. The center of the
74 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 76
coil of the auto transformer is connected through an induction coilto the other end of the tube. By this means the alternating currentimpulses are sent through the tube in one direction, one half cyclefrom one of the pairs of terminals of the tube, the other half cyclefrom the other terminal. Thus pulsating direct current, kept constantby the induction coil, flows through the tube, the pulsations over-lapping each other by the magnetic action of the choke coils. Thisalternating current lamp is started by the high voltage dischargemethod. It has a 50-inch length of tube, consuming about 400 watts
fro/js/brmer Pesistonce/^Je/vury
Storti/ip iK^ncfDiagram of Cooper-Hewitt Lamp for Use on Alternating Current.The mercury arc is inherently for use on direct current, butby means of reactance coils, it can be operated on alternatingcurrent.
on 1 10 volts. Its efficiency is a little less than that of the direct currentlamp. THE LUMINOUS OR MAGNETITE ARC LAMPAbout 1901 Dr. Charles P. Steinmetz, Schenectady, N. Y., studiedthe effect of metallic salts in the arc flame. Dr. Willis R. Whitney,also of Schenectady, and director of the research laboratory of theorganization of which Dr. Steinmetz is the consulting engineer, fol-lowed with some further work along this line. The results of thiswork were incorporated in a commercial lamp called the magnetite arclamp, through the efforts of C. A. B. Halvorson, Jr., at Lynn, Mass.The negative electrode consists of a pulverized mixture of magnetite
NO. 2 HISTORY OF ELECTRIC LIGHT SCHROEDER 75(a variety of iron ore) and other substances packed tightly in aniron tube. The positive electrode is a piece of copper sheathed iniron to prevent oxidization of the copper. The arc flame gives abrilliant white light, and, similar to the mercury arc, is inherentlylimited to direct current. It burns in the open air at about 75 volts.The lamp is made for 4-ampere direct current series circuits andconsumes about 310 watts and has an efficiency of about Ii-| lumensper watt.The negative (iron tube) electrode now has a life of about 350
LuAtiNOUS OR Magnetite Arc Lamp, 1902.This has a negative electrode containing magnetite which producesa very luminous white flame in the arc stream.
hours. Later, a higher efficiency, 4-ampere electrode was made whichhas a shorter life but gives an efficiency of about 17 1-p-w, and a 6.6-ampere lamp was also made giving an efficiency of about 18 1-p-w usingthe regular electrode. This electrode in being consumed gives offfumes, so the lamp has a chimney through its body to carry them off.Some of the fumes condense, leaving a fine powder, iron oxide, in theform of rust. The consumption of the positive (copper) electrode isvery slow, which is opposite to that of carbon arc lamps on directcurrent. The arc flame is brightest near the negative (iron tube)
76 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 76
electrode and decreases in brilliancy and volume as it nears the posi-tive (copper) electrode.The peculiarities of the arc are such that Halvorson invented anentirely new principle of control. The electrodes are normally apart.In starting, they are drawn together by a starting magnet with suffi-cient force to dislodge the slag which forms on the negative electrode
'^^i^iiDiagram of Series Magnetite Arc Lamp.The method of control, entirely different from that of otherarc lamps, was invented by Halvorson to meet the peculiarities ofthis arc.
and which becomes an insulator when cold. Current then flowsthrough the electrodes and through a series magnet which pulls up asolenoid breaking the circuit through the starting magnet. This allowsthe lower electrode to fall a fixed distance, about seven-eighths of aninch, drawing the arc, whose voltage is then about 72 volts. Asthe negative electrode is consumed, the length and voltage of the arc
NO. 2 HISTORY OF ELECTRIC LIGHT SCHROEDER 77increases when a magnet, in shunt with the arc, becomes sufficientlyenergized to close the contacts in the circuit of the starting magnetcausing the electrode to pick up and start off again.MERCURY ARC RECTIFIER FOR MAGNETITE ARC LAMPSAs the magnetite arc requires direct current for its operation, theobvious way to supply a direct constant current for series circuits isto rectify, by means of the mercury arc, the alternating current ob-
rmMercury Arc Rf.ctifier Tube for Series MagnetiteArc Lamps, 1902.The mercury arc converted the alternating constant current into directcurrent required by the magnetite lamp.tained from a constant current transformer. The terminals of themovable secondary coil of the constant current transformer are con-nected to the two arms of the rectifier tube. One end of the seriescircuit is connected to the center of the secondary coil. The otherend of the series circuit is connected to a reactance which in turn isconnected to the pool of mercury in the bottom of the rectifier tube.One-half of the cycle of the alternating current goes from thesecondary coil to one arm of the rectifier tube through the mercuryvapor, the mercury arc having already been started by a separate
78 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 76
starting electrode. It then goes to the pool of mercury, through thereactance and through the series circuit. The other half cycle ofalternating current goes to the other arm of the rectifier tuhe, throughthe mercury vapor, etc., and through the series circuit. Thus a pulsat-ing direct current flows through the series circuit, the magnetic actionof the reactance coil making the pulsations of current overlap eachother, which prevents the mercury arc from going out.
Eaklv Mercury Arc Rixtu-'iek Installation.
INCANDESCENT LAMP DEVELOPMENTS, 1894-I904With the development of a waterproof base in 1900, by the use ofa waterproof cement instead of plaster of Paris to fasten the base tothe bulb, porcelain at first and later glass being used to insulate theterminals of the base from each other, lamps could be exposed to theweather and give good results. Electric sign lighting therefore re-ceived a great stimulus, and lamps as low as 2 candlepower for novolts were designed for this purpose. Carbon lamps with concentratedfilaments were also made for stereoptican and other focussing pur-poses. These lamps were made in sizes from 20 to 100 candlepower.The arc lamp was more desirable for larger units.
NO. 2 HISTORY OF ELI-XTRIC LIGHT SCHROEDER 79The dry battery was made in small units of 2, 3 and 5 cells, sothat lamps of about -| to i candlepower were made for 2h, 33 and(4 volts, for portable flashlights. It was not however until thetungsten filament was developed in 1907 that these flashlights becameas popular as they now are. For ornamental lighting, lamps weresupplied in round and tuljular bulbs, usually frosted to soften thelight.
The AFoork Tube Light, 1904.This consisted of a tube about i}i inches in diameter and havinga length up to 200 feet, in which air at about one thousandth part ofatmospheric pressure was made to glow by a very high voltage alter-nating current. THE MOORE TUBE LIGHTGeissler, a German, discovered sixty odd years ago, that a highvoltage alternating current would cause a vacuum tube to glow. Thislight was similar to that obtained by Hawksbee over two hundredyears ago. Geissler obtained his high voltage alternating current by aspark coil, which consisted of two coils of wire mounted on an ironcore. Current from a primary battery passed through the primary
8o SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 76
coil, and this current was rapidly interrupted by a vibrator on theprinciple of an electric bell. This induced an alternating current ofhigh voltage in the secondary coil as this coil had a great many moreturns than the primary coil had. Scientists found that about 70 percent of the electrical energy put into the Geissler tube was convertedinto the actual energy in the light given out.In 1891 Mr. D. McFarlan Moore, an American, impressed with thefact that only one-half of one per cent of the electrical energy putinto the carbon-incandescent lamp came out in the form of light, de-cided to investigate the possibilities of the vacuum tube. Afterseveral years of experiments and the making of many trial lamps,
T,UBE DISTRIBUTED INANY FORM DESIREDTO LENGTHS OF 200 FT.
Diagram of Feeder Valve of Moore Tube.As the carbon terminals inside the tube absorbed the very slightamount of gas in the tube, a feeder valve allowed gas to flow in thetube, regulating the pressure to within one ten thousandth part of anatmosphere above and below the normal extremely slight pressurerequired.he finally, in 1904, made a lamp that was commercially used in con-siderable numbers.The first installation of this form of lamp was in a hardware storein Newark, N. J. It consisted of a glass tube if inches in diameterand 180 feet long. Air, at a pressure of about one-thousand part ofan atmosphere, was in the tube, from which was obtained a pale pinkcolor. High voltage (about 16,000 volts) alternating current wassupplied by a transformer to two carbon electrodes inside the endsof the tube. The air had to be maintained within one ten-thousandthpart of atmospheric pressure above and below the normal of one-thousandth, and as the rarefied air in the tube combined chemicallywith the carbon electrodes, means had to be devised to maintain the
NO. 2 HISTORY OF ELECTRIC LIGHT SCHROEDER 8l
air in the tube at this slight pressure as well as within the narrowlimits required.This was accomplished by a piece of carbon through which the aircould seep, but if covered with mercury would make a tight seal. Asthe air pressure became low, an increased current would flow throughthe tube, the normal being about a tenth of an ampere. This accord-ingly increased the current flowing through the primary coil of thetransformer. In series with the primary coil was an electro-magnetwhich lifted, as the current increased, a bundle of iron wires mountedin a glass tube which floated in mercury. The glass tube, rising,lowered the height of the mercury, uncovering a carbon rod cementedin a tube connecting the main tube with the open air. Thus air couldseep through this carbon rod until the proper amount was fed into themain tube. When the current came back to normal the electro-magnetlowered the floating glass tube which raised the height of the mercuryand covered the carbon rod, thus shutting off the further supply ofair.As there was a constant loss of about 400 watts in the transformer,and an additional loss of about 250 watts in the two electrodes, thetotal consumption of the 180-foot tube was about 2250 watts. Nitro-gen gas gave a yellow light, which was more efficient and so was laterused. On account of the fixed losses in the transformer and electrodesthe longer tubes were more efficient, though they were made in varioussizes of from 40 to 200 feet. The 200-foot tube, with nitrogen, hadan efficiency of about 10 lumens per watt. Nitrogen gas was suppliedthe tube by removing the oxygen from the air used. This was accom-plished by passing the air over phosphorous which absorbed theoxygen.Carbon dioxide gas (CO2) gave a pure white light but at about halfthe efficiency of nitrogen. The gas was obtained by allowing hydro-chloric acid to come in contact with lumps of marble (calcium carbo-nate) which set free carbon dioxide and water vapor. The latter wasabsorbed by passing the gas through lumps of calcium chloride. Thecarbon dioxide tube on account of its daylight color value, made anexcellent light under which accurate color matching could be done.A short tube is made for this purpose and this is the only use whichthe Moore tube now has, owing to the more efficient and simplertungsten filament incandescent lamp.
82 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 76THE OSMIUM LAMPDr. Auer von Welsbach, the German scientist who had producedthe Welsbach gas mantle, invented an incandescent electric lamphaving a filament of the metal osmium. It was commercially intro-duced in Europe in 1905 and a few were sold, but it was nevermarketed in this country. It was generally made for 55 volts, twolamps to burn in series on no-volt circuits, gave about 25 candle-power and had an initial efficiency of about 5^ lumens per watt. Ithad a very fair maintenance of candlepower during its life, havingan average efficiency of about 5 1-p-w. Osmium is a very rare andX /
\ 1' \
_.^ .|t....__
Osmium Lamp, 1905.This incandescent lamp was used in Europe for a few years, butwas impractical to manufacture in large quantities as osmium israrer and more expensive than platinum.
expensive metal, usually found associated with platinum, and is there-fore very difficult to obtain. Burnt out lamps were therefore boughtback in order to obtain a supply of osmium. It is also a very brittlemetal, so that the lamps were extremely fragile.THE GEM LAMPDr. Willis R. W'hitney, of Schenectady, N. Y., had invented anelectrical resistance furnace. This consisted of a hollow carbontube, packed in sand, through which a very heavy current could bepassed. This heated the tube to a very high temperature, the sandpreventing the tube from oxidizing, so that whatever was put insidethe tube could be heated to a very high heat. Among his various
NO. 2 HISTORY OF ELECTRIC LIGHT SCHROEDER 83
experiments, he heated some carbon filaments and found that the hightemperature changed their resistance " characteristic " from negativeto positive. The ordinary carbon filament has a resistance v^hen hotthat is less than when it is cold, which was reversed after heating itto the high temperature Dr. Whitney was able to obtain. These fila-ments were made into lamps for no-volt service and it was foundthat they could be operated at an efficiency of 4 lumens per watt. Thelamps also blackened less than the regular carbon lamp throughouttheir life.This lamp was put on the market in 1905 and was called the Gemor metallized carbon filament lamp as such a carbon filament had a
Gem Lamp, 1905.This incandescent lamp had a graphitized carbon filament obtainedby the heat of an electric furnace, so that it could be operated at25 per cent higher efficiency than the regular carbon lamp. This lampis in the exhibit of Edison lamps in the Smithsonian Institution.
resistance characteristic similar to metals. At first it had two singlehair pin filaments in series which in 1909 were changed to a singleloop filament like the carbon lamp.In 1905 the rating of incandescent lamps was changed from acandlepower to a wattage basis. The ordinary i6-candlepower carbonlamp consumed 50 watts and was so rated. The 50-watt Gem lampgave 20 candlepower, both candlepower ratings being their meancandlepower in a horizontal direction. The Gem lamp was made forno-volt circuits in sizes from 40 to 250 watts. The 50-watt sizewas the most popular, many millions of which were made before thelamp disappeared from use in 1918. The lamp was not quite asstrong as the carbon lamp. Some Gem lamps for series circuits were
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also made, but these were soon superseded by the tungsten-filamentlamp which appeared in 1907.THE TANTALUM LAMPDr. Werner von Bolton, a German physicist, made an investigationof various materials to see if any of them were more suitable thancarbon for an incandescent-lamp filament. After experimenting withvarious metals, tantalum was tried. Tantalum had been known toscience for about a hundred years. Von Bolton finally obtained someof the pure metal and found it to be ductile so that it could be drawn
\ "1
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Tantalum Lamp, 1906.The tantalum filament could be operated at 50 per cent greater effi-ciency than that of the regular carbon incandescent lamp. This lampis in the exhibit of Edison lamps in the Smithsonian Institution.
out into a wire. As it had a low specific resistance, the wire filamenthad to be much longer and thinner than the carbon filament. A greatnumber of experimental lamps were made so that it was not until1906 that the lamp was put on the market in this country. It had aninitial efficiency of 5 lumens per watt and a good maintenance ofcandle power throughout its life, having an average efficiency of about4I 1-p-w. Th© usual sizes of lamps were 40 and 80 watts givingabout 20 and 40 candlepower respectively. It was not quite asstrong as the carbon lamp, and on alternating current the wire crystal-lized more rapidly, so that it broke more easily, giving a shorter lifethan on direct current. It disappeared from use in 1913.
NO. 2 HISTORY OF ELECTRIC LIGHT SCHROEDER 85INVENTION OF THE TUNGSTEN LAMPAlexander Just and Franz Hanaman in 1902 were laboratory assis-tants to the Professor of Chemistry in the Technical High School inVienna. Just was spending his spare time in another laboratory inVienna, attempting to develop a boron incandescent lamp. In Augustof that year he engaged Hanaman to aid him in his work. They con-ceived the idea of making a lamp with a filament of tungsten and fortwo years worked on both lamps. The boron lamp turned out to bea failure. Their means were limited ; Hanaman's total income was$44 ])er month and Just's was slightly more than this. In 1903 theytook out a German patent on a tungsten filament, but the process theydescribed was a failure because it produced a filament containingboth carbon and tungsten. The carbon readily evaporated and quicklyblackened the bulb when they attempted to operate the filament at anefficiency higher than that possible with the ordinary carbon filament.Finally in the latter part of the next year (1904) they were able toget rid of the carbon and produced a pure tungsten filament.Tungsten had been known to chemists for many years by its com-pounds, its oxides and its alloys with steel, but the properties of thepure metal were practically unknown. It is an extremely hard andbrittle metal and it was impossible at that time to draw it into a wire.Just and Hanaman's process of making a pure tungsten filament con-sisted of taking tungsten oxide in the form of an extremely finepowder, reducing this to pure tungsten powder by heating it whilehydrogen gas passed over it. The gas combined with the oxygenof the oxide, forming water vapor which was carried off, leaving thetungsten behind.The tungsten powder was mixed with an organic binding material,and the paste was forced by very high pressure through a hole drilledin a diamond. This diamond die was necessary because tungsten,being so hard a substance, would quickly wear away any other kind ofdie. The thread formed was cut into proper lengths, bent the shape ofa hair pin and the ends fastened to clamps. Current was passedthrough the hair pin in the presence of hydrogen gas and watervapor. The current heated the hair pin, carbonized the organic bind-ing material in it, the carbon then combining with the moist hydrogengas, leaving the tungsten particles behind. These particles weresintered together by the heat, forming the tungsten filament. Patentswere applied for in various countries, the one in the United States onJuly 6, 1905.
86 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. ']6The two laboratory assistants in 1905 finally succeeded in gettingtheir invention taken up by a Hungarian lamp manufacturer. By theend of the year lamps were made that were a striking success for theycould be operated at an efficiency of 8 lumens per watt. They wereput on the American market in 1907, the first lamp put out being thelOO-watt size for iio-volt circuits. This was done by mountingseveral hair pin loops in series to get the requisite resistance, tungstenhaving a low specific resistance. The issue of the American patent
Tungsten Lamp, 1907.The original 100 watt tungsten lamp was nearly three times as effi-cient as the carbon lamp, but its " pressed " filament was very fragile.This lamp is in the exhibit of Edison lamps in the SmithsonianInstitution.
was delayed owing to an interference between four different parties,each claiming to be the inventor. After prolonged hearings, oneapplication having been found to be fraudulent, the patent was finallygranted to Just and Hanaman on February 27, 1912.This " pressed " tungsten filament was quite fragile, but on accountof its relatively high efficiency compared with other incandescentlamps, it immediately became popular. Soon after its introductionit became possible to make finer filaments so that lamps for 60, 40
NO. 2 HISTORY OF ELECTRIC LIGHT SCHROEDER 8/
and then 25 watts for iio-volt circuits were made available. Sizesup to 500 watts were also made which soon began to displace theenclosed carbon arc lamp. Lamps were also made for series circuitsin sizes from 32 to 400 candlepower. These promptly displaced thecarbon and Gem series lamps. The high efficiency of the tungstenfilament was a great stimulus to flashlights which are now sold by themillions each year. The lighting of railroad cars, Pullmans andcoaches, with tungsten lamps obtaining their current from storagebatteries, soon superseded the gas light formerly used. In some cases,a dynamo, run by a belt from the car axle, kept these batteriescharged.
Drawn Tungsten Wire Lamp, 1911.Scientists had declared it impossible to change tungsten from abrittle to ductile metal. This, however, was accomplished byDr. Coolidge, and drawn tungsten wire made the lamp very sturdy.This lamp is in the exhibit of Edison lamps in the SmithsonianInstitution. DRAWN TUNGSTEN WIREAfter several years of patient experiment. Dr. Williain D. Coolidgein the research laboratory of a large electrical manufacturing com-pany at Schenectady, N. Y., invented a process for making tungstenductile, a patent for which was obtained in December, 191 3. Tungstenhad heretofore been known as a very brittle metal, but by means ofthis process it became possible to draw it into wire. This greatly sim-plified the manufacture of lamps and enormously improved theirstrength. Such lamps were commercially introduced in 1911.With drawn tungsten wire it was easier to coil and therefore con-centrate the filament as required by focusing types of lamps. The
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automobile headlight lamp was among the first of these, which in 19 12started the commercial use of electric light on cars in place of oiland acetylene gas. On street railway cars the use of tungsten lamps,made possible on this severe service by the greater sturdiness of thedrawn wire, greatly improved their lighting. Furthermore, as thevoltage on street railway systems is subject to great changes, thecandlepower of the tungsten filament has the advantage of varyingbut about half as much as that of the carbon lamp on fluctuatingvoltage.
Quartz Mercury Vapor Lamp, 1912.The mercury arc if enclosed in quartz glass can be operated atmuch higher temperature and therefore greater efficiency. The lightis still deficient in red but gives a considerable amount of ultraviolet rays which kill bacteria and are very dangerous to the eye.They can, however, be absorbed by a glass globe. The lamp is notused as an illuminant in this country, but is valuable for use in thepurification of water.THE QUARTZ MERCURY VAPOR ARC LAMPBy putting a mercury arc in a tube made of quartz instead of glass,it can be operated at a much higher temperature and thereby obtaina greater efficiency. Such a lamp, however, is still largely deficientin red rays, and it gives out a considerable amount of ultra-violetrays. These ultra-violet rays will kill bacteria and the lamp is beingused to a certain extent for such purpose as in the purification ofwater. These rays are very dangerous to the eyes, but they are ab-sorbed by glass, so as an illuminant, a glass globe must be used on thelamp. These lamps appeared in Europe about 1912 but were never
NO. 2 HISTORY OF ELECTRIC LIGHT SCHROEDER 89
used to any extent in this country as an illuminant. They have anefficiency of about 26 lumens per watt. Quartz is very difficult towork, so the cost of a quartz tube is very great. The ordinary bun-sen gas flame is used with glass, but quartz will only become soft inan oxy-hydrogen or oxy-acetylene flame.
Gas Filled Tungsten Lamp, 1913.By operating a coiled filament in an inert gas, Dr. Langmuir wasable to greatly increase its efficiency, the gain in light by the highertemperature permissible, more than offsetting the loss of heat by con-vection of the gas. This lamp is in the exhibit of Edison lamps in theSmithsonian Institution.THE GAS-FILLED TUNGSTEN LAMPThe higher the temperature at which an incandescent lamp fila-ment can be operated, the more efficient it becomes. The limit intemperature is reached when the material begins to evaporate rapidly,which blackens the bulb. The filament becoming thinner more quickly,thus rupturing sooner, shortens the life. If, therefore, the evaporat-ing temperature can by some means be slightly raised, the efficiencywill be greatly improved. This was accomplished by Dr. IrvingLangmuir in the research laboratories at Schenectady, N. Y., byoperating a tungsten filament in an inert gas. Nitrogen was first
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used. The gas circulating in the bull:) has the disadvantage of conduct-ing heat away from the filament so that the filament w^as coiled. Thispresented a smaller surface to the currents of gas and thereby reducedthis loss. The lamps were commercially introduced in 191 3 and apatent was granted in April, 1 91 6.An increased amount of electrical energy is required in these lampsto offset the heat being conducted away by the gas. This heat lossis minimized in a vacuum lamp, the filament tending to stay hot on theprinciple of the vacuum bottle. This loss in a gas filled lamp becomesrelatively great in a filament of small diameter, as the surface in pro-portion to the volume of the filament increases with decreasing diam-
r'r*^.
Gas Filled Tungsten Lamp, 1923.This is the form of the lamp as at present made. For iio-voltcircuits the sizes range from 50 to 1000 watts.
eters. Hence there is a point where the gain in temperature is offsetby the heat loss. The first lamps made were of 750 and 1000 watts forI lo-volt circuits. Later 500- and then 400-watt lamps were made. Theuse of argon gas, which has a poorer heat conductivity than nitrogen,made it possible to produce smaller lamps, 50-watt gas-filled lamps foriio-volt circuits now being the smallest available. In the presentstate of the art, a vacuum lamp is more efficient than a gas-filled lamphaving a filament smaller than one consuming about half an ampere.Thus gas-filled lamps are not now practicable much below 100 wattsfor 220 volts, 50 watts for no volts, 25 watts for 60 volts, 15 wattsfor 30 volts, etc.From the foregoing it will be seen that the efficiency of these lampsdepends largely on the diameter of the filament. There are other
NO. 2 HISTORY OF ELECTRIC LIGHT SCHROEDER 9I
considerations, which also apply to vacuum lamps, that affect theefificiency. Some of these are: the number of anchors used, as theyconduct heat away ; in very low voltage lamps having short filamentsthe relative amount of heat conducted away by the leading-in wiresbecomes of increasing importance, etc. The looo-watt lamp for iio-volt circuits is now made for nearly 20^ lumens per watt ; the 50-wattlamp a little over 10 1-p-w.The advent of the tungsten filament and especially the gas-filledlamp sounded the doom of all other electric illuminants except themagnetite and mercury arc lamps. All other incandescent lamps havenow practically disappeared. The flame arc as well as the enclosedcarbon arc lamp are hardly ever seen. The simplicity of the incan-descent lamp, its cleanliness, low first cost, low maintenance cost andhigh efficiency of the tungsten filament have been the main reasonsfor its popularity.
TYPES AND SIZES OF TUNGSTEN LAMPS NOW MADEThere are about two hundred different types and sizes of tungstenfilament lamps now standard for various kinds of lighting service.For iio-volt service, lamps are made in sizes from 10 to 1000 watts.Of the smaller sizes, some are made in round and tubular-shaped bulbsfor ornamental lighting. In addition there are the candelabra lampsused in ornamental fixtures. Twenty-five- to five hundred-watt lampsare made with bulbs of special blue glass to cut out the excess of redand yellow rays and thus produce a light approximating daylight.For 220-volt service lamps are made in sizes of from 25 to 1000watts. For sign lighting service, 5-watt lamps of low voltage aremade for use on a transformer located near the sign to reduce theno volts alternating current to that required by the lamps. Lampsare made from 5 to 100 watts for 30-volt service, such as is found intrain lighting and in gas engine driven dynamo sets used in ruralhomes beyond the reach of central station systems. Concentratedfilament lamps are made for stereopticon and motion picture projec-tion, floodlighting, etc., in sizes from 100 to 1000 watts, for streetrailway headlights in sizes below 100 watts and for locomotive head-lights in sizes from 100 to 250 watts. For series circuits, used instreet lighting, lamps are made from 60 to 2500 candlepower. ^linia-ture lamps cover those for flashlight, automobile, Christmas-tree,surgical and dental services, etc. They range, depending on theservice, from ^ to 21 candlepower, and in voltage from 2^ to 24.
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Stanuakd Tungsten Lamps, 1923.This illustrates some of the two hundred different lampsregularly made.
NO. 2 HISTORY OF ELECTRIC LIGHT SCHROEDER 93STANDARD VOLTAGESMention has been made of no-volt service, 220-volt service, etc.In the days of the carbon incandescent lamp it was impossible tomanufacture all lamps for an exact predetermined voltage. Thepopular voltage was no, so ligliting companies were requested in anumber of instances to adjust their service to some voltage otherthan no. They were thus able to utilize the odd voltage lampsmanufactured, and this produced a demand for lamps of variousvoltages from 100 to 130. Arc lamps had a resistance (reactance onalternating current) that was adjustable for voltages between 100and 130.Similarly a demand was created for lamps of individual voltagesof from 200 to 260. The 200- to 260-volt range has simmered downto 220, 230, 240 and 250 volts. These lamps are not as efficient asthe no-volt type and their demand is considerably less, as the no-volt class of service for lighting is, with the exception of England,almost universal. Thus no-volt service means 100 to 130 volts incontra-distinction to 200 to 260 volts, etc. The drawn tungsten wirefilament made it possible to accurately predetermine the voltage ofthe lamp, so now that the carbon incandescent lamp is a thing of thepast, there is no need for so many different voltages. Several yearsago standard voltages of no, 115 and 120 were recommended foradoption by all the electrical societies in the United States, and practi-cally all central stations have now changed their service to one ofthese voltages.COST OF INCANDESCENT ELECTRIC LIGHTIn the early '8o's current was expensive, costing a consumer on theaverage about twenty cents per kilowatt hour. The cost has graduallycome down and the general average rate for which current is soldfor lighting purposes is now about 4^ cents. During the period 1880to 1905 the average efBciency of carbon lamps throughout their lifeincreased from about one to over 2f lumens per watt and their listprice decreased from one dollar to twenty cents. The average amountof light obtained for one cent at first was about five candlepower hoursand in 1904 it was increased to over thirty-six at the average ratethen in effect. The next year with the more efificient Gem lamp 44candle-hours could be had for one cent. In 1906 the amount wasincreased to 50 with the tantalum lamp and with the tungsten lampin 1907, even at its high price of $1.50, the amount was furtherincreased to 63. Since then the average cost of current has been
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reduced but slightly, but the efficiency of the tungsten lamp hasmaterially increased and its cost reduced so that it is now possible toobtain, with the ordinary 40-watt lamp 170 candle-hours for a cent.If the gas-filled tungsten lamp were used the amount of light nowobtained for a cent would depend upon the size, which, for the 1000-watt lamp, would be 382 candle-hours.
STATISTICS REGARDING THE PRESENT DEMAND FOR LAMPSIn the United States there are about 350 million incandescent andabout two hundred thousand magnetite arc lamps now (1923) in use.They are increasing about 10 per cent each year. The annual demandfor incandescent lamps for renewals and new installations is over200 millions, exclusive of miniature lamps. The use of incandescentlamps in all other countries put together is about equal that in the U. S.The average candlepower of standard lighting lamps has increasedfrom 16, which prevailed during the period prior to 1905, to over 60.The average wattage has not varied much during the past twenty-oddyears, the average lamp now consuming about 55 watts. This indi-cates that the public is utilizing the improvement in lamp efficiencyby increased illumination. The present most popular lamp is the 40-watt size which represents 20 per cent of the total demand. Secondin demand is the 25-watt at 18 per cent and third, the 50-watt at 15per cent of the totalin numbers. While the aggregate demand of allthe gas-filled tungsten lamps is a little over 20 per cent in numbers,they represent, on account of their greater efficiency and wattage, overhalf the amount of total candlepower used. In the United Statesabout 85 per cent of all lamps are for the iio-volt range. About 5per cent for 220 volts, 2 per cent for street series lighting, 3 per centfor street railway and 5 per cent for trainlighting and miscellaneousclasses of service.
SELECTED BIBLIOGRAPHYAlglave and Boulard, " The Electric Light/' translated byT. O'Connor Sloane, edited by C. M. Liingren, D. Appleton &Co., New York, 1884.Barham, G. Basil, " The Development of the Incandescent ElectricLamp," Scott Greenwood & Son, London, 1912.Dredge, James, " Electric Illumination," 2 vols., John Wiley & Sons,New York, 1882.DuRGiN, William A., " Electricity—Its History and Development,"A. C. McClurg & Co., Chicago, 1912.Dyer & Martin, " Edison, His Life and Inventions," 2 vols., Harper& Bros., New York, 1910.GuiLLEMiN, Amedee, " Electricity and Magnetism," edited by Sil-vanus P. Thompson, McMillan & Co., London, 1891.Houston, Edwin J., " Electricity One Hundred Years ago and To-day," The W. J. Johnston Co., New York, 1894.Houston and Kennelly, " Electric Arc Lighting," McGraw Pub-lishing Co., New York, 1906.Hutchinson, Rollin W., Jr., " High Efficiency Electrical lUumi-nants and Illumination," John Wiley & Sons, New York, 191 1.Maier, Julius, " Arc and Glow Lamps," Whittaker & Co., London,1886.Pope, Franklin Leonard, " Evolution of the Electric IncandescentLamp," Boschen & Wefer, New York, 1894.Solomon, Maurice, " Electric Lamps," D. Van Nostrand Co., NewYork, 1908.