Chapter I: Part 1

Transcriber’s Notes

In this Plain Text version of this eBook, italics are enclosed within ~tildas~, superscripts and subscripts are enclosed in curly braces and preceded by a caret ^{superscript} or an underscore _{subscript}.

Other notes will be found at the end of this eBook.

SMITHSONIAN MISCELLANEOUS COLLECTIONS
VOLUME 76, NUMBER 2

HISTORY OF ELECTRIC LIGHT

BY
HENRY SCHROEDER
Harrison, New Jersey

SMITHSONIAN
INSTITVTION
WASHINGTON 1846]

(PUBLICATION 2717)

CITY OF WASHINGTON
PUBLISHED BY THE SMITHSONIAN INSTITUTION
AUGUST 15, 1923

The Lord Baltimore Press
BALTIMORE, MD., U. S. A.

CONTENTS

PAGE

List of Illustrations v

Foreword ix

Chronology of Electric Light xi

Early Records of Electricity and Magnetism 1

Machines Generating Electricity by Friction 2

The Leyden Jar 3

Electricity Generated by Chemical Means 3

Improvement of Volta’s Battery 5

Davy’s Discoveries 5

Researches of Oersted, Ampère, Schweigger and Sturgeon 6

Ohm’s Law 7

Invention of the Dynamo 7

Daniell’s Battery 10

Grove’s Battery 11

Grove’s Demonstration of Incandescent Lighting 12

Grenet Battery 13

De Moleyns’ Incandescent Lamp 13

Early Developments of the Arc Lamp 14

Joule’s Law 16

Starr’s Incandescent Lamp 17

Other Early Incandescent Lamps 19

Further Arc Lamp Developments 20

Development of the Dynamo, 1840–1860 24

The First Commercial Installation of an Electric Light 25

Further Dynamo Developments 27

Russian Incandescent Lamp Inventors 30

The Jablochkoff “Candle” 31

Commercial Introduction of the Differentially Controlled Arc Lamp 33

Arc Lighting in the United States 33

Other American Arc Light Systems 40

“Sub-Dividing the Electric Light” 42

Edison’s Invention of a Practical Incandescent Lamp 43

Edison’s Three-Wire System 53

Development of the Alternating Current Constant Potential System 54

Incandescent Lamp Developments, 1884–1894 56

The Edison “Municipal” Street Lighting System 62

The Shunt Box System for Series Incandescent Lamps 64

The Enclosed Arc Lamp 65

The Flame Arc Lamp 67

The Constant Current Transformer for Series Circuits 69

Enclosed Series Alternating Current Arc Lamps 69

Series Incandescent Lamps on Constant Current Transformers 70

The Nernst Lamp 71

The Cooper-Hewitt Lamp 72

The Luminous or Magnetite Arc Lamp 74

Mercury Arc Rectifier for Magnetite Arc Lamps 77

Incandescent Lamp Developments, 1894–1904 78

The Moore Tube Light 79

The Osmium Lamp 82

The Gem Lamp 82

The Tantalum Lamp 84

Invention of the Tungsten Lamp 85

Drawn Tungsten Wire 87

The Quartz Mercury Vapor Arc Lamp 88

The Gas-Filled Tungsten Lamp 89

Types and Sizes of Tungsten Lamps Now Made 91

Standard Voltages 93

Cost of Incandescent Electric Light 93

Statistics Regarding the Present Demand for Lamps 94

Selected Bibliography 95

LIST OF ILLUSTRATIONS

PAGE

Portion of the Electrical Exhibit in the United States National
Museum viii

Otto Von Guericke’s Electric Machine, 1650 2

Voltaic Pile, 1799 4

Faraday’s Dynamo, 1831 8

Pixii’s Dynamo, 1832 9

Daniell’s Cell, 1836 10

Grove’s Cell, 1838 11

Grove’s Incandescent Lamp, 1840 13

De Moleyns’ Incandescent Lamp, 1841 14

Wright’s Arc Lamp, 1845 15

Archereau’s Arc Lamp, 1848 16

Starr’s Incandescent Lamp, 1845 18

Staite’s Incandescent Lamp, 1848 19

Roberts’ Incandescent Lamp, 1852 19

Farmer’s Incandescent Lamp, 1859 20

Roberts’ Arc Lamp, 1852 21

Slater and Watson’s Arc Lamp, 1852 21

Diagram of “Differential” Method of Control of an Arc Lamp 22

Lacassagne and Thiers’ Differentially Controlled Arc Lamp, 1856 23

Serrin’s Arc Lamp, 1857 24

Siemens’ Dynamo, 1856 25

Alliance Dynamo, 1862 26

Wheatstone’s Self-Excited Dynamo, 1866 27

Gramme’s Dynamo, 1871 28

Gramme’s “Ring” Armature 28

Alteneck’s Dynamo with “Drum” Wound Armature, 1872 29

Lodyguine’s Incandescent Lamp, 1872 30

Konn’s Incandescent Lamp, 1875 30

Bouliguine’s Incandescent Lamp, 1876 31

Jablochkoff “Candle,” 1876 32

Jablochkoff’s Alternating Current Dynamo, 1876 33

Wallace-Farmer Arc Lamp, 1875 34

Wallace-Farmer Dynamo, 1875 34

Weston’s Arc Lamp, 1876 35

Brush’s Dynamo, 1877 36

Diagram of Brush Armature 36

Brush’s Arc Lamp, 1877 37

Thomson-Houston Arc Dynamo, 1878 38

Diagram of T-H Arc Lighting System 39

Thomson-Houston Arc Lamp, 1878 40

Thomson Double Carbon Arc Lamp 40

Maxim Dynamo 41

Sawyer’s Incandescent Lamp, 1878 42

Farmer’s Incandescent Lamp, 1878 42

Maxim’s Incandescent Lamp, 1878 43

Edison’s First Experimental Lamp, 1878 44

Diagram of Constant Current Series System 45

Diagram of Edison’s Multiple System, 1879 45

Edison Dynamo, 1879 46

Edison’s High Resistance Platinum Lamp, 1879 47

Edison’s High Resistance Platinum in Vacuum Lamp, 1879 47

Edison’s Carbon Lamp of October 21, 1879 48

Demonstration of Edison’s Incandescent Lighting System 49

Dynamo Room, S. S. Columbia 50

Original Socket for Incandescent Lamps 51

Wire Terminal Base Lamp, 1880 51

Original Screw Base Lamp, 1880 52

Improved Screw Base Lamp, 1881 52

Final Form of Screw Base, 1881 53

Diagram of Edison’s Three Wire System, 1881 54

Diagram of Stanley’s Alternating Current Multiple System, 1885 55

Standard Edison Lamp, 1884 56

Standard Edison Lamp, 1888 56

Standard Edison Lamp, 1894 57

Various Bases in Use, 1892 58

Thomson-Houston Socket 59

Westinghouse Socket 59

Adapters for Edison Screw Sockets, 1892 60

Various Series Bases in Use, 1892 61

Edison “Municipal” System, 1885 62

Edison “Municipal” Lamp, 1885 63

Shunt Box System, 1887 64

Enclosed Arc Lamp, 1893 65

Open Flame Arc Lamp, 1898 66

Enclosed Flame Arc Lamp, 1908 66

Constant Current Transformer, 1900 68

Series Incandescent Lamp Socket with Film Cutout, 1900 70

Nernst Lamp, 1900 71

Diagram of Nernst Lamp 72

Cooper-Hewitt Mercury Vapor Arc Lamp, 1901 73

Diagram of Cooper-Hewitt Lamp for Use on Alternating Current 74

Luminous or Magnetite Arc Lamp, 1902 75

Diagram of Series Magnetite Arc Lamp 76

Mercury Arc Rectifier Tube for Series Magnetite Arc Circuits, 1902 77

Early Mercury Arc Rectifier Installation 78

The Moore Tube Light, 1904 79

Diagram of Feeder Valve of Moore Tube 80

Osmium Lamp, 1905 82

Gem Lamp, 1905 83

Tantalum Lamp, 1906 84

Tungsten Lamp, 1907 86

Drawn Tungsten Wire Lamp, 1911 87

Quartz Mercury Vapor Lamp, 1912 88

Gas Filled Tungsten Lamp, 1913 89

Gas Filled Tungsten Lamp, 1923 90

Standard Tungsten Lamps, 1923 92

Section devoted to the historical development of the electric light and dynamo.]

FOREWORD

In the year 1884 a Section of Transportation was organized in the United States National Museum for the purpose of preparing and assembling educational exhibits of a few objects of railroad machinery which had been obtained both from the Centennial Exhibition held in Philadelphia in 1876 and still earlier as incidentals to ethnological collections, and to secure other collections relating to the railway industry.

From this beginning the section was expanded to include the whole field of engineering and is designated at present as the Divisions of Mineral and Mechanical Technology. The growth and enlargement of the collections has been particularly marked in the fields of mining and mineral industries; mechanical engineering, especially pertaining to the steam engine, internal combustion engine and locomotive; naval architecture, and electrical engineering, particularly the development of the telegraph, telephone and the electric light.

In the acquisition of objects visualizing the history of electric light the Museum has been rather fortunate, particularly as regards the developments in the United States. Thus mention may be made of the original Patent Office models of the more important dynamos, arc lights and incandescent lights, together with original commercial apparatus after these models; a unit of the equipment used in the first commercially successful installation on land of an incandescent lighting system, presented by Joseph E. Hinds in whose engraving establishment in New York City the installation was made in 1881; and a large series of incandescent lights, mainly originals, visualizing chronologically the developments of the Edison light from its inception, presented at intervals since the year 1898 by the General Electric Company.

The object of all collections in the Divisions is to visualize broadly the steps by which advances have been made in each field of engineering; to show the layman the fundamental and general principles which are the basis for the developments; and to familiarize the engineer with branches of engineering other than his own. Normally when a subject is completely covered by a collection of objects, a paper is prepared and published describing the collection and the story it portrays. In the present instance, however, on account of the uncertainty of the time of completing the collection, if it is possible ever to bring this about, it was thought advisable to publish Mr. Schroeder’s paper which draws upon the Museum collection as completely as possible.

CARL W. MITMAN,
~Curator, Divisions of Mineral and
Mechanical Technology,
U. S. National Museum~.

CHRONOLOGY OF ELECTRIC LIGHT

1800--Allesandro Volta demonstrated his discovery that electricity
can be generated by chemical means. The VOLT, the unit of
electric pressure, is named in his honor for this discovery
of the electric battery.

1802--Sir Humphry Davy demonstrated that electric current can heat
carbon and strips of metal to incandescence and give light.

1809--Sir Humphry Davy demonstrated that current will give a
brilliant flame between the ends of two carbon pencils
which are first allowed to touch each other and then pulled
apart. This light he called the “arc” on account of its
arch shape.

1820--André Marie Ampère discovered that current flowing through
a coiled wire gives it the properties of a magnet. The
AMPERE, the unit of flow of electric current, is named in
his honor for this discovery.

1825--Georg Simon Ohm discovered the relation between the voltage,
ampereage and resistance in an electric circuit, which is
called Ohm’s Law. The OHM, the unit of electric resistance,
is named in his honor for this discovery.

1831--Michael Faraday discovered that electricity can be generated
by moving a wire in the neighborhood of a magnet, the
principle of the dynamo.

1840--Sir William Robert Grove demonstrated his experimental
incandescent lamp in which platinum is made incandescent by
current flowing through it.

1841--Frederick De Moleyns obtained the first patent on an
incandescent lamp. The burner was powdered charcoal
operating in an exhausted glass globe.

1845--Thomas Wright obtained the first patent on an arc light.

1845--J. W. Starr invented an incandescent lamp consisting of a
carbon pencil operating in the vacuum above a column of
mercury.

1856--Joseph Lacassagne and Henry Thiers invented the
“differential” method of control of the arc which was
universally used twenty years later when the arc lamp was
commercially established.

1862--The first commercial installation of an electric light. An
arc light was put in a lighthouse in England.

1866--Sir Charles Wheatstone invented the “self-excited” dynamo,
now universally used.

1872--Lodyguine invented an incandescent lamp having a graphite
burner operating in nitrogen gas.

1876--Paul Jablochkoff invented the “electric candle,” an arc light
commercially used for lighting the boulevards in Paris.

1877–8--Arc light systems commercially established in the United
States by William Wallace and Prof. Moses Farmer, Edward
Weston, Charles F. Brush and Prof. Elihu Thomson and Edwin
J. Houston.

1879--Thomas Alva Edison invented an incandescent lamp consisting
of a high resistance carbon filament operating in a
high vacuum maintained by an all glass globe. These
principles are used in all incandescent lamps made today.
He also invented a completely new system of distributing
electricity at constant pressure, now universally used.

1882--Lucien Goulard and John D. Gibbs invented a series
alternating current system of distributing electric
current. This has not been commercially used.

1886--William Stanley invented a constant pressure alternating
current system of distribution. This is universally used
where current is to be distributed long distances.

1893--Louis B. Marks invented the enclosed carbon arc lamp.

1898--Bremer’s invention of the flame arc lamp, having carbons
impregnated with various salts, commercially established.

1900--Dr. Walther Nernst’s invention of the Nernst lamp
commercially 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 light
commercially established.

1902--The magnetite arc lamp was developed by C. A. B. Halvorson,
Jr. This has a new method of control of the arc. The
negative electrode consists of a mixture of magnetite and
other substances packed in an iron tube.

1904--D. McFarlan Moore’s invention of the Moore vacuum tube light
commercially established. This consisted of a long tube,
made in lengths up to 200 feet, from which the air had been
exhausted to about a thousandth of an atmosphere. High
voltage current passing through this rarefied atmosphere
caused it to glow. Rarefied carbon dioxide gas was later
used.

1905--Dr. Auer von Welsbach’s invention of the osmium incandescent
lamp commercially established, but only on a small scale
in Europe. The metal osmium, used for the filament which
operated in vacuum, is rarer and more expensive than
platinum.

1905--Dr. Willis R. Whitney’s invention of the Gem incandescent
lamp commercially established. The carbon filament had been
heated to a very high temperature in an electric resistance
furnace invented by him. The lamp was 25 per cent more
efficient than the regular carbon lamp.

1906--Dr. Werner von Bolton’s invention of the tantalum
incandescent lamp commercially established.

1907--Alexander Just and Franz Hanaman’s invention of the tungsten
filament incandescent lamp commercially established.

1911--Dr. William D. Coolidge’s invention of drawn tungsten wire
commercially established.

1913--Dr. Irving Langmuir’s invention of the gas-filled tungsten
filament incandescent lamp commercially established.

HISTORY OF ELECTRIC LIGHT

BY HENRY SCHROEDER,
HARRISON, NEW JERSEY.

EARLY RECORDS OF ELECTRICITY AND MAGNETISM

About 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 attract iron. Lodestone is an iron ore (Fe_{3}O_{4}), having magnetic qualities and is now called magnetite. The word “magnet” comes from the fact that the best specimens of lodestones came from Magnesia, a city in Asia Minor. Plutarch, a Greek biographer, wrote about 100 A. D., that iron is sometimes attracted and at other times repelled by a lodestone. This indicates that the piece of iron was magnetised by the lodestone.

In 1180, Alexander Neckham, an English Monk, described the compass, which probably had been invented by sailors of the northern countries of Europe, although its invention has been credited to the Chinese. Early compasses probably consisted of an iron needle, magnetised by a lodestone, mounted on a piece of wood floating in water. The word lodestone or “leading stone” comes from the fact that it would point towards the north if suspended like a compass.

William Gilbert, physician to Queen Elizabeth of England, wrote a book about the year 1600 giving all the information then known on the subject. He also described his experiments, showing, among other things, the existence of magnetic lines of force and of north and south poles in a magnet. Robert Norman had discovered a few years previously that a compass needle mounted on a horizontal axis would dip downward. Gilbert cut a large lodestone into a sphere, and observed that the needle did not dip at the equator of this sphere, the dip increasing to 90 degrees as the poles were approached. From this he deduced that the earth was a magnet with the magnetic north pole at the geographic north pole. It has since been determined that these two poles do not coincide. Gilbert suggested the use of the dipping needle to determine latitude. He also discovered that other substances, beside amber, would attract light objects if rubbed.

MACHINES GENERATING ELECTRICITY BY FRICTION

Otto Von Guericke was mayor of the city of Magdeburg as well as a philosopher. About 1650 he made a machine consisting of a ball of sulphur mounted on a shaft which could be rotated. Electricity was generated when the hand was pressed against the globe as it rotated. He also discovered that electricity could be conducted away from the globe by a chain and would appear at the other end of the chain. Von Guericke also invented the vacuum air pump. In 1709, Francis Hawksbee, an Englishman, made a similar machine, using a hollow glass globe which could be exhausted. The exhausted globe when rotated at high speed and rubbed by hand would produce a glowing light. This “electric light” as it was called, created great excitement when it was shown before the Royal Society, a gathering of scientists, in London.

A ball of sulphur was rotated, electricity being generated when it rubbed against the hand.]

Stephen Gray, twenty years later, showed the Royal Society that electricity could be conducted about a thousand feet by a hemp thread, supported by silk threads. If metal supports were used, this could not be done. Charles du Fay, a Frenchman, repeated Gray’s experiments, and showed in 1733 that the substances which were insulators, and which Gilbert had discovered, would become electrified if rubbed. Those substances which Gilbert could not electrify were conductors of electricity.

THE LEYDEN JAR

The thought came to Von Kleist, Bishop of Pomerania, Germany, about 1745, that electricity could be stored. The frictional machines generated so small an amount of electricity (though, as is now known, at a very high pressure--several thousand volts) that he thought he could increase the quantity by storing it. Knowing that glass was an insulator and water a conductor, he filled a glass bottle partly full of water with a nail in the cork to connect the machine with the water. Holding the bottle in one hand and turning the machine with the other for a few minutes, he then disconnected the bottle from the machine. When he touched the nail with his other hand he received a shock which nearly stunned him. This was called the Leyden jar, the forerunner of the present condenser. It received its name from the fact that its discovery was also made a short time after by experimenters in the University of Leyden. Further experiments showed that the hand holding the bottle was as essential as the water inside, so these were substituted by tin foil coatings inside and outside the bottle.

Benjamin Franklin, American statesman, scientist and printer, made numerous experiments with the Leyden jar. He connected several jars in parallel, as he called it, which gave a discharge strong enough to kill a turkey. He also connected the jars in series, or “in cascade” as he called it, thus establishing the principle of parallel and series connections. Noticing the similarity between the electric spark and lightning, Franklin in 1752, performed his famous kite experiment. Flying a kite in a thunderstorm, he drew electricity from the clouds to charge Leyden jars, which were later discharged, proving that lightning and electricity were the same. This led him to invent the lightning rod.

ELECTRICITY GENERATED BY CHEMICAL MEANS

Luigi Galvani was an Italian scientist. About 1785, so the story goes, his wife was in delicate health, and some frog legs were being skinned to make her a nourishing soup. An assistant holding the legs with a metal clamp and cutting the skin with a scalpel, happened to let the clamp and scalpel touch each other. To his amazement the frog legs twitched. Galvani repeated the experiment many times by touching the nerve with a metal rod and the muscle with a different metal rod and allowing the rods to touch, and propounded the theory of 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. He found that the extent of the movement of the frog legs depended on the metals used for the rods, and thus believed that the electric charge was produced by the contact of dissimilar metals with the moisture in the muscles. To prove his point he made a pile of silver and zinc discs with cloths, wet with salt water, between them. This was in 1799, and he described his pile in March, 1800, in a letter to the Royal Society in London.

Volta discovered that electricity could be generated by chemical means and made a pile of silver and zinc discs with cloths, wet with salt water, between them. This was the forerunner of the present-day dry battery. Photograph courtesy Prof. Chas. F. Chandler Museum, Columbia University, New York.]

This was an epoch-making discovery as it was the forerunner of the present-day primary battery. Volta soon found that the generation of electricity became weaker as the cloths became dry, so to overcome this he made his “crown of cups.” This consisted of a series of cups containing salt water in which strips of silver and zinc were dipped. Each strip of silver in one cup was connected to the zinc strip in the next cup, the end strips of silver and zinc being terminals of the battery. This was the first time that a continuous supply of electricity in reasonable quantities was made available, so the VOLT, the unit of electrical pressure was named in his honor. It was later shown that the chemical affinity of one of the metals in the liquid was converted into electric energy. The chemical action of Volta’s battery is that the salt water attacks the zinc when the circuit is closed forming zinc chloride, caustic soda and hydrogen gas. The chemical equation is:

Zn + 2NaCl + 2H_{2}O = ZnCl_{2} + 2NaOH + H_{2}

IMPROVEMENT OF VOLTA’S BATTERY

It was early suggested that sheets of silver and zinc be soldered together back to back and that a trough be divided into cells by these bimetal sheets being put into grooves cut in the sides and bottom of the trough. 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 by the acid forming zinc sulphate and hydrogen gas, thus:

Zn + H_{2}SO_{4} = ZnSO_{4} + H_{2}

The hydrogen gas appears as bubbles on the copper and reduces the open circuit voltage (about 0.8 volt per cell) as current is taken from the battery. This is called “polarization.” Owing to minute impurities in the zinc, it is attacked by the acid even when no current is taken from the battery, the impurities forming with the zinc a short circuited local cell. This is called “local action,” and this difficulty was at first overcome by removing the zinc from the acid when the battery was not in use.

DAVY’S DISCOVERIES

Sir Humphry Davy was a well-known English chemist, and with the aid of powerful batteries constructed for the Royal Institution in London, he made numerous experiments on the chemical effects of electricity. He decomposed a number of substances and discovered the elements boron, potassium and sodium. He heated strips of various metals to incandescence by passing current through them, and showed that platinum would stay incandescent for some time without oxidizing. This was about 1802.

In the early frictional machines, the presence of electricity was shown by the fact that sparks could be obtained. Similarly the breaking 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 the large battery of 2000 cells he had had constructed. Using two sticks of charcoal connected by wires to the terminals of this very powerful battery, he demonstrated before the Royal Society the light produced by touching the sticks together and then holding them apart horizontally about three inches. The brilliant flame obtained he called an “arc” because of its arch shape, the heated gases, rising, assuming this form. Davy was given the degree of LL. D. for his distinguished research work, and was knighted on the eve of his marriage, April 11, 1812.

RESEARCHES OF OERSTED, AMPÈRE, SCHWEIGGER AND STURGEON

Hans Christian Oersted was a professor of physics at the University of Copenhagen in Denmark. One day in 1819, while addressing his students, he happened to hold a wire, through which current was flowing, over a large compass. To his surprise he saw the compass was deflected from its true position. He promptly made a number of experiments and discovered that by reversing the current the compass was deflected in the opposite direction. Oersted announced his discovery in 1820.

André Marie Ampère was a professor of mathematics in the Ecole Polytechnic in Paris. Hearing of Oersted’s discovery, he immediately made some experiments and made the further discovery in 1820 that if the wire is coiled and current passed through it, the coil had all 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 very sensitive instrument for measuring electric currents. It consisted of a delicate compass needle suspended in a coil of many turns of wire. Current in the coil deflected the needle, the direction and amount of deflection indicating the direction and strength of the current. Ampère further made the discovery that currents in opposite directions repel and in the same directions attract each other. He also gave a rule for determining the direction of the current by the deflection of the compass needle. He developed the theory that magnetism is caused by electricity flowing around the circumference of the body magnetised. The AMPERE, the unit of flow of electric current, was named in honor of his discoveries.

In 1825 it was shown by Sturgeon that if a bar of iron were placed in the coil, its magnetic strength would be very greatly increased, which he called an electro-magnet.

OHM’S LAW

Georg Simon Ohm was born in Bavaria, the oldest son of a poor blacksmith. With the aid of friends he went to college and became a teacher. It had been shown that the rate of transfer of heat from one end to the other of a metal bar is proportional to the difference of temperature between the ends. About 1825, Ohm, by analogy and experiment, found that the current in a conductor is proportional to the difference of electric pressure (voltage) between its ends. He further showed that with a given difference of voltage, the current in different conductors is inversely proportional to the resistance of the conductor. Ohm therefore propounded the law that the current flowing in a circuit is equal to the voltage on that circuit divided by the resistance of the circuit. In honor of this discovery, the unit of electrical resistance is called the OHM. This law is usually expressed as:

C = E/R

“C” meaning current (in amperes), “E” meaning electromotive force or voltage (in volts) and “R” meaning resistance (in ohms).

This is one of the fundamental laws of electricity and if thoroughly understood, will solve many electrical problems. Thus, if any two of the 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. Several trolley cars at the end of a line take 100 amperes to run them and the resistance of the overhead wire from the power house to the trolley cars is half an ohm; the drop in voltage on the line between the power house and trolley cars is therefore 50 volts, so that if the voltage at the 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 position as teacher in the High School in Cologne. Finally after ten years Ohm began to find supporters and in 1841 his law was publicly recognized by the Royal Society of London which presented him with the Copley medal.

INVENTION OF THE DYNAMO

Michael Faraday was an English scientist. Born of parents in poor circumstances, he became a bookbinder and studied books on electricity and chemistry. He finally obtained a position as laboratory assistant to Sir Humphry Davy helping him with his lectures and experiments. He also made a number of experiments himself and succeeded in liquifying chlorine gas for which he was elected to a Fellowship in the Royal Institution in 1824. Following up Oersted’s and Ampère’s work, he endeavored to find the relation between electricity and magnetism. Finally on Oct. 17, 1831, he made the experiment of moving a permanent bar magnet in and out of a coil of wire connected to a galvanometer. This generated electricity in the coil which deflected the galvanometer needle. A few days after, Oct. 28, 1831, he mounted a copper disk on a shaft so that the disk could be rotated between the poles of a permanent horseshoe magnet. The shaft and edge of the disk were connected by brushes and wires to a galvanometer, the needle of which was deflected as the disk was rotated. A paper on his invention was read before the Royal Society on November 24, 1831, which appeared in printed form in January, 1832.

Faraday discovered that electricity could be generated by means of a permanent magnet. This principle is used in all dynamos.]

Faraday did not develop his invention any further, being satisfied, as in all his work, in pure research. His was a notable invention but it remained for others to make it practicable. Hippolyte Pixii, a Frenchman, made a dynamo in 1832 consisting of a permanent horseshoe magnet which could be rotated between two wire bobbins mounted on a soft iron core. The wires from the bobbins were connected to a pair of brushes touching a commutator mounted on the shaft holding the magnet, and other brushes carried the current from the commutator so that the alternating current generated was rectified into direct current.

Pixii made an improvement by rotating a permanent magnet in the neighborhood of coils of wire mounted on a soft iron core. A commutator rectified the alternating current generated into direct current. This dynamo is in the collection of the Smithsonian Institution.]

E. M. Clarke, an Englishman made, in 1834, another dynamo in which the bobbins rotated alongside of the poles of a permanent horseshoe magnet. He also made a commutator so that the machine produced direct current. None of these machines gave more than feeble current at low pressure. The large primary batteries that had been made were much more powerful, although expensive to operate. It has been estimated that the cost of current from the 2000-cell battery to operate the demonstration of the arc light by Davy, was six dollars a minute. At present retail rates for electricity sold by lighting companies, six dollars would operate Davy’s arc light about 500 hours or 30,000 times as long.

DANIELL’S BATTERY

Daniell invented a battery consisting of zinc, copper and copper sulphate. Later the porous cup was dispensed with, which was used to keep the sulphuric acid formed separate from the solution of copper sulphate, the two liquids then being kept apart by their difference in specific gravity. It was then called the Gravity Battery and for years was used in telegraphy.]

It was soon discovered that if the zinc electrode were rubbed with mercury (amalgamated), the local action would practically cease, and if the hydrogen bubbles were removed, the operating voltage of the cell would be increased. John Frederic Daniell, an English chemist, invented a cell in 1836 to overcome these difficulties. His cell consisted of a glass jar containing a saturated solution of copper sulphate (CuSO_{4}). A copper cylinder, open at both ends and perforated with holes, was put into this solution. On the outside of the copper cylinder there was a copper ring, located below the surface of the solution, acting as a shelf to support crystals of copper sulphate. Inside the cylinder there was a porous earthenware jar containing dilute sulphuric acid and an amalgamated zinc rod. The two liquids were therefore kept apart but in contact with each other through the pores of the jar. The hydrogen gas given off by the action of the sulphuric acid on the zinc, combined with the dissolved copper sulphate, formed sulphuric acid and metallic copper. The latter was deposited 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 + H_{2}SO_{4} = ZnSO_{4} + H_{2}
In outer glass jar: H_{2} + CuSO_{4} = H_{2}SO_{4} + Cu

This cell had an open circuit voltage of a little over one volt. Later the porous cup was dispensed with, the two liquids being kept apart by the difference of their specific gravities. This was known as the Gravity cell, and for years was used in telegraphy.

This consisted of zinc, sulphuric acid, nitric acid and platinum. It made a very powerful battery. The nitric acid is called the depolarizer as it absorbs the hydrogen gas formed, thus improving the operating voltage.]

GROVE’S BATTERY

Sir William Robert Grove, an English Judge and scientist, invented a cell in 1838 consisting of a platinum electrode in strong nitric acid in a porous earthenware jar. This jar was put in dilute sulphuric acid in a glass jar in which there was an amalgamated zinc plate for the other electrode. This had an open circuit voltage of about 1.9 volts. The porous jar was used to prevent the nitric acid from attacking the zinc. The nitric acid was used for the purpose of combining with the hydrogen gas set free by the action of the sulphuric acid on the zinc, and hence was the depolarizing agent. Hydrogen combining with nitric acid forms nitrous peroxide and water. Part of the nitrous peroxide is dissolved in the water, and the rest escapes as fumes which, however, are very suffocating.

The chemical equations of this cell are as follows:

In outer glass jar: Zn + H_{2}SO_{4} = ZnSO_{4} + H_{2}
In inner porous jar: H_{2} + 2HNO_{3} = N_{2}O_{4} + 2H_{2}O

An interesting thing about Grove’s cell is that it was planned in accordance with a theory. Grove knew that the electrical energy of the zinc-sulphuric acid cell came from the chemical affinity of the two reagents, and if the hydrogen gas set free could be combined with oxygen (to form water--H_{2}O), such chemical affinity should increase the strength of the cell. As the hydrogen gas appears at the other electrode, the oxidizing agent should surround that electrode. Nitric acid was known at that time as one of the most powerful oxidizing liquids, but as it attacks copper, he used platinum for the other electrode. Thus he not only overcame the difficulty of polarization by the hydrogen gas, but also increased the voltage of the cell by the added chemical action of the combination of hydrogen and oxygen.

GROVE’S DEMONSTRATION OF INCANDESCENT LIGHTING

In 1840 Grove made an experimental lamp by attaching the ends of a coil of platinum wire to copper wires, the lower parts of which were well varnished for insulation. The platinum wire was covered by a glass tumbler, the open end set in a glass dish partly filled with water. This prevented draughts of air from cooling the incandescent platinum, and the small amount of oxygen of the air in the tumbler reduced the amount of oxidization of the platinum that would otherwise occur. With current supplied by a large number of cells of his battery, he lighted the auditorium of the Royal Institution with these lamps during one of the lectures he gave. This lamp gave only a feeble light as there was danger of melting the platinum and platinum gives 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 cool the incandescent platinum. The demonstration was only of scientific interest, the cost of current being much too great (estimated at several hundred dollars a kilowatt hour) to make it commercial.

GRENET BATTERY

It was discovered that chromic anhydride gives up oxygen easier than nitric acid and consequently if used would give a higher voltage than Grove’s nitric acid battery. It also has the advantage of a lesser tendency to attack zinc directly if it happens to come in contact with it. Grenet developed a cell having a liquid consisting of a mixture of potassium bichromate (K_{2}Cr_{2}O_{7}) and sulphuric acid. A porous cell was therefore not used to keep the two liquids apart. This had the advantage of reducing the internal resistance. The chemical reaction was:

K_{2}Cr_{2}O_{7} (potassium bichromate) + 7H_{2}SO_{4} (sulphuric
acid) + 3Zn (zinc) = 3ZnSO_{4} (zinc sulphate) + K_{2}SO_{4}
(potassium sulphate) + Cr_{2} (SO_{4})_{3} (chromium sulphate)
+ 7H_{2}O (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 the neck of the bottle-shaped jar containing the liquid.

Grove made an experimental lamp, using platinum for the burner which was protected from draughts of air by a glass tumbler.]

DE MOLEYNS’ INCANDESCENT LAMP

Frederick De Moleyns, an Englishman, has the honor of having obtained the first patent on an incandescent lamp. This was in 1841 and 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 platinum wire, the end below the tube being coiled. Another platinum wire coiled at its upper end came up through the lower part of the globe but did not quite touch the other platinum coil. The powdered charcoal filled the two coils of platinum wire and bridged the gap between. Current passing through this charcoal bridge heated it to incandescence. The air in the globe having been removed as far as was possible with the hand air pumps then available, the charcoal did not immediately burn up, the small amount consumed being replaced by the supply in the tube. The idea was ingenious but the lamp was impractical as the globe rapidly blackened from the evaporation of the incandescent charcoal.

This consisted of two coils of platinum wire containing powdered charcoal operating in a vacuum. It is only of interest as the first incandescent lamp on which a patent (British) was granted.]

EARLY DEVELOPMENTS OF THE ARC LAMP

It had been found that most of the light of the arc came from the tip of the positive electrode, and that the charcoal electrodes were rapidly consumed, the positive electrode about twice as fast as the negative. Mechanisms were designed to take care of this, together with devices to start the arc by allowing the electrodes to touch each other and then pulling them apart the proper distance. This distance varied from one-eighth to three-quarters of an inch.

In 1840 Bunsen, the German chemist who invented the bunsen burner, devised a process for making hard dense carbon pencils which lasted much longer than the charcoal previously used. The dense carbon from the inside of the retorts of gas making plants was ground up and mixed with molasses, moulded into shape and baked at a high temperature. Bunsen also, in 1843, cheapened Grove’s battery by substituting a hard carbon plate in place of the platinum electrode.

This lamp is also only of interest as the first arc lamp on which a patent (British) was granted. Four arcs played between the five carbon discs.]

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 of five carbon disks normally touching each other and rotated by clockwork. Two of the disks could be drawn outward by thumb screws, which was to be done after the current was turned on thus establishing four arcs, one between each pair of disks. The next year, 1846, W. E. Staite, another Englishman, made an arc lamp having two vertical carbon pencils. The upper was stationary. The lower was movable and actuated by clockwork directed by ratchets which in turn were regulated by an electro-magnet controlled by the current flowing through the arc. Thus the lower carbon would be moved up or down as 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 piece of iron which could be drawn down into a coil of wire. The weight 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 and through the coil of wire (solenoid) which then became energized and pulled the lower carbon down, thus striking the arc. Two of these arc lamps were installed in Paris and caused considerable excitement. After a few weeks of unreliable operation, it was found that the cost of current from the batteries was much too great to continue their use commercially. The dynamo had not progressed far enough to permit its use.

This simple arc was controlled by an electro-magnet, and two lamps were installed for street lighting in Paris, current being obtained from batteries.]

JOULE’S LAW

Joule was an Englishman, and in 1842 began investigating the relation between mechanical energy and heat. He first showed that, by allowing a weight to drop from a considerable height and turn a paddle wheel in water, the temperature of the water would increase in relation to the work done in turning the wheel. It is now known that 778 foot-pounds (1 lb. falling 778 feet, 10 lbs. falling 77.8 feet or 778 lbs. falling one foot, etc.) is the mechanical equivalent of energy equal to raising one pound of water one degree Fahrenheit. 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 next investigated the relation between heat and electric current. He made a device consisting of a vessel of water in which there were a thermometer and an insulated coil of wire having a considerable resistance. He found that an electric current heated the water, and making many combinations of the amount and length of time of current flowing and of the resistance of the wire, he deduced the law that the energy in an electric circuit is proportional to the square of the amount of current flowing multiplied by the length of time and multiplied by the resistance of the wire.

The rate of electrical energy (electric power) is therefore proportional to the square of current multiplied by the resistance. The electrical unit of power is now called the WATT, named in honor of James Watt, the Englishman, who made great improvements to the steam engine about a century ago. Thus, watts = C^{2}R and substituting the value of R from Ohm’s law, C = E/R, we get

Watts = Volts × Amperes

The watt is a small unit of electric power, as can be seen from the fact that 746 watts are equal to one horsepower. The kilowatt, kilo being the Greek word for thousand, is 1000 watts.

This term is an important one in the electrical industry. For example, dynamos are rated in kilowatts, expressed as KW; the largest one made so far is 50,000 KW which is 66,666 horsepower. Edison’s first commercial dynamo had a capacity of 6 KW although the terms watts and kilowatts were not in use at that time. The ordinary sizes of incandescent lamps now used in the home are 25, 40 and 50 watts.

STARR’S INCANDESCENT LAMP

This consisted of a short carbon pencil operating in the vacuum above a column of mercury.]

J. W. Starr, an American, of Cincinnati, Ohio, assisted financially by Peabody, the philanthropist, went to England where he obtained a patent in 1845 on the lamps he had invented, although the patent was taken out under the name of King, his attorney. One is of passing interest only. It consisted of a strip of platinum, the active length of which could be adjusted to fit the battery strength used, and was covered 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 consisted of a rod of carbon operating in the vacuum above a column of mercury (Torrecellium vacuum) as in a barometer. A heavy platinum wire was sealed in the upper closed end of a large glass tube, and connected to the carbon rod by an iron clamp. The lower end of the carbon rod was fastened to another iron clamp, the two clamps being held in place and insulated from each other by a porcelain rod. Attached to the lower clamp was a long copper wire. Just below the lower clamp, the glass tube was narrowed down and had a length of more than 30 inches. The tube was then filled with mercury, the bottom of the tube being put into a vessel partly full of mercury. The mercury ran out of the enlarged upper part of the tube, coming to rest in the narrow part of the tube as in a barometer, so that the carbon rod was then in a vacuum. One lamp terminal was the platinum wire extending through the top of the tube, and the other was the mercury. Several of these lamps were put on exhibition in London, but were not a commercial success as they blackened very rapidly. Starr started his return trip to the United States the next year, but died on board the ship when he was but 25 years old.

OTHER EARLY INCANDESCENT LAMPS

The burner was of platinum and iridium.]

It had a graphite burner operating in vacuum.]

In 1848 W. E. Staite, who two years previously had made an arc lamp, invented an incandescent lamp. This consisted of a platinum-iridium burner in the shape of an inverted U, covered by a glass globe. It had a thumb screw for a switch, the whole device being mounted on a bracket which was used for the return wire. E. C. Shepard, another Englishman, obtained a patent two years later on an incandescent lamp consisting of a weighted hollow charcoal cylinder the end of which pressed against a charcoal cone. Current passing through this high resistance contact, heated the charcoal to incandescence. It operated in a glass globe from which the air could be exhausted. M. J. Roberts obtained an English patent in 1852 on an incandescent lamp. This had a graphite rod for a burner, which could be renewed, mounted in a glass globe. The globe was cemented to a metallic cap fastened to a piece of pipe through which the air could be exhausted. After being exhausted, the pipe, having a stop cock, could be screwed on a stand to support the lamp.

Moses G. Farmer, a professor at the Naval Training Station at Newport, Rhode Island, lighted the parlor of his home at 11 Pearl Street, Salem, Mass., during July, 1859, with several incandescent lamps having a strip of platinum for the burner. The novel feature of this lamp was that the platinum strip was narrower at the terminals than in the center. Heat is conducted away from the terminals and by making the burner thin at these points, the greater resistance of the ends of the burner absorbed more electrical energy thus offsetting the heat being conducted away. This made a more uniform degree of incandescence throughout the length of the burner, and Prof. Farmer obtained a patent on this principle many years later (1882).

This experimental platinum lamp was made by Professor Farmer and several of them lighted the parlor of his home in Salem, Mass.]

FURTHER ARC LAMP DEVELOPMENTS

During the ten years, 1850 to 1860, several inventors developed arc lamp mechanisms. Among them was M. J. Roberts, who had invented the graphite incandescent lamp. In Roberts’ arc lamp, which he patented in 1852, the lower carbon was stationary. The upper carbon fitted snugly into an iron tube. In the tube was a brass covered iron rod, which by its weight could push the upper carbon down the tube so the two carbons normally were in contact. An electro-magnet in series with the arc was so located that, when energized, it pulled up the iron tube. This magnet also held the brass covered iron rod from pushing the upper carbon down the tube so that the two carbons were pulled apart, striking the arc. When the arc went out, the iron tube dropped back into its original position, the brass covered iron rod was released, pushing the upper carbon down the tube until the two carbons again touched. This closed the circuit again, striking the arc as before.

The arc was controlled by an electro-magnet which held an iron tube to which the upper carbon was fastened.]

Clutches were used for the first time in this arc lamp to feed the carbons.]

In the same year (1852) Slater and Watson obtained an English patent on an arc lamp in which the upper carbon was movable and held in place by two clutches actuated by electro-magnets. The lower carbon was fixed, and normally the two carbons touched each other. When current was turned on, the electro-magnet lifted the clutches which 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 to feed as it became consumed.

Henry Chapman, in 1855, made an arc in which the upper carbon was allowed to feed by gravity, but held in place by a chain wound around a wheel. On this wheel was a brake actuated by an electro-magnet. The lower carbon was pulled down by an electro-magnet working against a spring. When no current was flowing or when the arc went out, the two carbons touched. With current on, one electro-magnet set the brake and held the upper carbon stationary. The other electro-magnet pulled the lower carbon down, thus striking the arc.

None of these mechanisms regulated the length of the arc. It was not until 1856 that Joseph Lacassagne and Henry Thiers, Frenchmen, invented the so-called “differential” method of control, which made the carbons feed when the arc voltage, and hence length, became too great. This principle was used in commercial arc lamps several years afterward when they were operated on series circuits, as it had the added advantage of preventing the feeding of one arc lamp affecting another on the same circuit. This differential control consists in principle of two electro-magnets, one in series with, and opposing the pull of the other which is in shunt with the arc. The series magnet pulls the carbons apart and strikes the arc. As the arc increases in length, its voltage rises, thereby increasing the current flowing through the shunt magnet. This increases the strength of the shunt magnet and, when the arc becomes too long, the strength of the shunt becomes greater than that of the series magnet, thus making the carbons feed.

This principle, invented by Lacassagne and Thiers, was used in all arc lamps when they were commercially introduced on a large scale more than twenty years later.]

The actual method adopted by Lacassagne and Thiers was different from this, but it had this principle. They used a column of mercury on which the lower carbon floated. The upper carbon was stationary. The height of the mercury column was regulated by a valve connected with a reservoir of mercury. The pull of the series magnet closed the valve fixing the height of the column. The pull of the shunt magnet tended to open the valve, and when it overcame the pull of the series magnet it allowed mercury to flow from the reservoir, raising the height of the column bringing the carbons nearer together. This reduced the arc voltage and shunt magnet strength until the valve closed again. Thus the carbons were always kept the proper distance apart. In first starting the arc, or if the arc should go out, current would only flow through the shunt magnet, bringing the two carbons together until they touched. Current would then flow through the contact of the two carbons and through the series magnet, shutting the valve. There were no means of pulling the carbons apart to strike the arc. Current flowing through the high resistance of the poor contact of the two carbons, heated their tips to incandescence. The incandescent tips would begin to burn away, thus after a time starting an arc. The arc, however, once started was maintained the proper length.

The lower carbon floated on a column of mercury whose height was “differentially” controlled by series and shunt magnets.]

In 1857, Serrin took out his first patent on an arc lamp, the general principles of which were the same as in others he made. The mechanism consisted of two drums, one double the diameter of the other. Both carbons were movable, the upper one feeding down, and the lower one feeding up, being connected with chains wound around the drums. The difference in consumption of the two carbons was therefore compensated for by the difference in size of the drums, thus maintaining the location of the arc in a fixed position. A train of wheels controlled by a pawl and regulated by an electro-magnet, controlled the movement of the carbons. The weight of the upper carbon and its holder actuates the train of wheels.

This type of arc was not differentially controlled but was the first commercial lamp later used. Both carbons were movable, held by chains wound around drums which were controlled by ratchets actuated by an electro-magnet.]

DEVELOPMENT OF THE DYNAMO, 1840–1860