History Of The Incandescent Lamp - By John W. Howell And Henry Schroeder (1927)

You are reading: Chapter 1: Development of Electric Lighting Prior to Edison's Invention






The word electricity originates from the Greek name for amber, "elektron;" Thales, a Greek philosopher having recorded the fact about twenty-five centuries ago that if amber is rubbed it will attract objects of light weight. About two hundred and fifty years later Aristotle, another Greek philosopher, found that a mineral, later called lodestone and now known to be the iron ore magnetite, would attract iron. The word magnet comes from the fact that lodestones were first found near Magnesia, a city in Asia Minor. The word lodestone, an abbreviation for "leading stone", comes from the fact, probably discovered by sailors in the northern countries of Europe, although it has been often credited to the Chinese, that this mineral would point to the north if suspended like a compass.


William Gilbert, physician to Queen Elizabeth of England, made a number of experiments, among which was the discovery of magnetic lines of force, and of north and south poles in a magnet. He wrote a book about the year 1600 summarizing the then known facts about electricity and magnetism. A few years previously Robert Norman had discovered that the amount of dip of the compass needle varied at different points on the sphere. From this he deduced that the earth was a magnet and assumed that the magnetic and geographic north poles were the same. It has since been found that these poles do not coincide. Gilbert also discovered that many substances beside amber would also attract light objects if rubbed.


Otto Von Guericke, about 1650, made a machine consisting of a ball of sulphur mounted on a shaft which could be rotated. Electricity was generated when the shaft was rotated and the hand lightly pressed against the rotating sulphur ball. He also discovered that the electricity generated could be conducted away from the sulphur ball by a metal chain from which sparks could be obtained. Francis Hawksbee, about sixty years later, made a similar machine, using a hollow glass globe from which the air had been exhausted by the vacuum pump that had been invented by Von Guericke.




Electricity was generated by friction between the hand and the rotating sulphur ball.



This exhausted globe when rotated at high speed and rubbed against the hand produced a glow of light. This electric light, as it was called, created a great excitement when it was shown before the Royal Society, a gathering of English scientists. Those machines were forerunners of the frictional glass disc machines which generate electricity at very high pressures (but in very small quantities) so that long sparks can be produced. They are now occasionally used for medical purposes.


Stephen Gray, about 1729, demonstrated before, the Royal Society that electricity could be conducted about a thousand feet by a hemp thread. This was possible if the hemp thread was supported by silk thread but could not be done if metal supports were used. Charles duFay, in 1733, showed that those substances, which Gilbert had found could be electrified if rubbed, were insulators; and those substances which could not be electrified were conductors of electricity.


Von Kleist, about 1745, invented the so-called Leyden jar, the forerunner of the present condenser, in attempting to store electricity. The name came from the fact that it was independently discovered shortly afterward by experimenters in the University of Leyden. Von Kleist, knowing that the frictional machines generated so small a quantity of electricity, thought he could store it in a glass bottle full of water, as water was known to be a conductor and glass an insulator. In the bottle was a cork with a nail through it, the nail touching the water inside. Holding the bottle in one hand and turning a frictional machine with the other, the machine being connected to the nail in the cork, he proceeded to fill the bottle with electricity. After turning the machine for a few moments he pulled the bottle away from it and then touched the nail with his hand. The shock threw him down and nearly stunned him. Later it was found that the hand holding the bottle was as essential as the water inside, both being later replaced by tin foil.


Benjamin Franklin made numerous experiments with the Leyden jar. He connected several jars in parallel and produced a discharge strong enough to kill a fowl. He also connected jars in series (in "cascade" he called it), thereby establishing the principle of parallel and series connections. Franklin's most famous experiment is his proof that lightning is electricity. This he did in 1752, by flying a kite in a thunderstorm, and drawing electricity from the clouds with which he charged Leyden jars and drew sparks from a key attached to the kite string. It is a wonder that he was not killed by this experiment. These experiments led to his invention of the lightning rod.




Volta discovered the principle of the present day primary battery, one form of which is the so-called dry battery used for flashlights and in radio. This was the first time that electricity could be obtained in considerable quantity and the VOLT is named after him in honor of this discovery.  Photograph, courtesy of Charles P. Chandler Museum, Columbia University, New York.


Volta's Invention of the Primary Battery

About 1785, so it is said, the wife of Luigi Galvani, an Italian scientist, was in delicate health. Some frogs' legs were being skinned to make her a nourishing soup. Galvani's 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 frogs' legs twitched. Galvani repeated the experiment and proposed a theory of animal electricity in a paper he published in 1791.


Allesandro Volta, a professor of physics at the University of Pavia in Italy, repeated Galvani's experiments and found that the clamp and scalpel must be of different metals. He believed that the electric charge which made the muscles in the frogs' legs convulse was caused by the action of the moisture in the muscles on the different metals. Following up this idea, he made a pile of silver and zinc discs, probably coins, with pieces of cloth wet with salt water between them. From this Voltaic Pile, as it was called, he found that electricity could be obtained. In March, 1800, he sent a letter to the Royal Society in London, describing his invention, and the VOLT, the unit of electrical pressure, was named after him in honor of this discovery.


It was later shown that the chemical affinity of one of the metals for the liquid was converted into electrical energy. In Volta's Pile the zinc combines chemically with the salt water when a wire is connected to the silver and zinc terminals, forming zinc chloride, caustic soda and hydrogen gas.


A more powerful battery was made by the use of copper, zinc and dilute sulphuric acid. The zinc combining with the sulphuric acid forms zinc sulphate and hydrogen gas. The latter appears as bubbles on the copper plate and reduces the voltage of the battery, this being called "polarization." Minute impurities in the zinc will cause the zinc to be attacked even when the circuit is open, as the impurities form a local short circuited cell. This is called "local action," and in order to prevent the zinc from being uselessly consumed, it was removed from the dilute acid when the battery was not in use. Later it was found that this difficulty could be largely overcome if the zinc electrode were rubbed with a little mercury, so that its surface became amalgamated.



Improvements in Batteries

The main difficulty with the copper-zinc-sulphuric acid battery was the formation of hydrogen gas bubbles on the copper electrode (polarization) which greatly reduced its operating voltage, and it was found that if the bubbles were removed, by brushing them off with a stick of wood for instance, the capacity of the battery would be greatly increased.


In 1836, John Frederic Daniell, an English chemist, invented a chemical means of overcoming this difficulty. He made a battery consisting of an amalgamated zinc rod in dilute sulphuric acid, as in the previous batteries. These were placed in a porous earthenware jar which was put in a saturated solution of copper sulphate, thus the dilute sulphuric acid was kept physically separate from the copper sulphate solution, but the two liquids were in electrical contact with each other through the pores of the porous cup.


The other electrode was copper and was immersed in the copper sulphate solution. The chemical action of the battery was that the zinc combining with the sulphuric acid formed zinc sulphate and hydrogen gas as before. The hydrogen gas going through the pores of the cup combined with the copper sulphate, forming sulphuric acid and metallic copper, the latter being deposited on the copper electrode. Crystals of copper sulphate were kept in the copper sulphate solution to maintain it in a saturated condition. Later the porous cup was dispensed with, the two solutions being kept apart by their difference in specific gravity. This was called the gravity battery, and for many years was used in telegraphy. The voltage of this battery was about one volt per cell.


Sir William Robert Grove made a notable further improvement in batteries. It was known that the electrical energy of the zinc-sulphuric acid cell came from the chemical affinity of the two, and that if the hydrogen gas set free could be combined with oxygen, to form water, such additional chemical affinity would increase the strength of the cell. Nitric acid was known to be a very active oxidizing agent, but as it attacks copper, platinum was substituted as the material for the positive electrode, where the hydrogen gas bubbles appear.


In 1840 Sir Robert made a battery consisting of a platinum electrode in strong nitric acid which was kept in the inner porous jar to prevent it from attacking the zinc electrode. This combination was put in dilute sulphuric acid containing the amalgamated zinc rod electrode. The hydrogen gas, liberated by the action of the sulphuric acid on the zinc, combined with the nitric acid to form nitrous peroxide and water. Part of the nitrous peroxide dissolved in the water and the rest escaped in the form of very suffocating fumes. This battery had almost double the strength of previous batteries, having a voltage of about 1.9 volts.


Some years later Grenet improved the battery by substituting a solution of potassium bichromate for the nitric acid. This solution could be mixed directly with the sulphuric acid, as it does not attack zinc to a great extent. The porous jar was, therefore, unnecessary and no fumes were formed. To lessen the cost, a slab of carbon was used for the positive electrode. The zinc electrode was fastened to a sliding rod so that it could be drawn up into the neck of the bottle shaped jar containing the liquid, to prevent the useless consumption of zinc when the battery was not in use.



The Ampere

André Marie Ampère was a professor of mathematics in the Polytechnic School in Paris. In 1820 Oersted, a professor of physics in the University of Copenhagen in Denmark, had announced his accidental discovery that current flowing in a wire would deflect a compass from its true position. Ampère repeated Oersted's experiments and made a number of others from which he developed several fundamental laws regarding current flowing in a wire. He also discovered that current flowing in a coil of wire gave it the properties of a magnet, and thus established the long sought connection between electricity and magnetism. The AMPERE, the unit of flow of electric current, was named for him in honor of his discoveries.



Ohm's Law

About the most important fundamental law of electricity was discovered in 1825, by Georg Simon Ohm, a teacher in the High School in Cologne. It was known that the rate of transfer of heat from one end of a metal bar to the other was in proportion to the difference in temperature between the ends. By analogy and experiment, Ohm found that the current in a wire is proportional to the difference of voltage (electric pressure) between the ends of the wire. He also showed that the current in the wire is inversely proportional to the electrical resistance of the wire. With these as a basis, Ohm propounded the law that the current flowing in a circuit is equal to the voltage divided by the resistance. In honor of this discovery, the OHM, the unit of electrical resistance, was named after him.


As often happens in such cases, critics derided this law, and in this case the criticism was so severe that Ohm was forced out of his position in the High School. Having been born of parents in poor circumstances, and worked his way through college in order to obtain an education, he keenly felt the criticism which forced him to give up the sort of work for which he had so earnestly striven. He went back to his parents and worked in his father's blacksmith shop for over ten years. Finally he began to find supporters to his theory and in 1841 his law was publicly recognized by the Royal Society in London, which presented him with the Copley medal.


This simple law is at first difficult to understand, but if once mastered will solve many electrical problems. It is usually expressed as:



C =



"C" meaning Current (in amperes)

"E" meaning Electromotive Force (in volts)

"R" meaning Resistance (in ohms)


If two of the factors in the above formula are known, the third can be readily determined. For example, an incandescent lamp, burning on a circuit whose voltage (pressure) is known to be 120, is found to consume ½ an ampere of current. The electrical resistance of such a lamp is therefore 240 ohms.


Perhaps the simplest analogy to an electrical circuit is a hydraulic system. The voltage in an electrical system is similar to the pounds per square inch pressure in the hydraulic system. The amperes flowing in an electric circuit are similar to the gallons per minute of water flowing in a pipe; it is the rate of flow, not the actual volume. This is often the stumbling block to the uninitiated. Another term similar to the ampere is rate of speed, which is usually expressed in miles per hour. The difference between a rate and an actual volume may be shown, for example, by the size of an automobile storage battery which is expressed in ampere-hours; that is, a 120 ampere-hour battery is one which has the capacity to deliver 15 amperes continuously for eight hours. Similarly a 120 gallon tank will deliver 15 gallons of water per minute for eight minutes; or an automobile traveling fifteen miles per hour will take eight hours to cover 120 miles.


The resistance of an electrical circuit is generally quite easy to understand. It is similar to the friction that water encounters in flowing through a pipe. A large pipe will allow water to flow through it quite easily, and therefore, has a low resistance in the same sense that a large wire has a low electric resistance.



The Invention of the Dynamo

Schweigger, familiar with Oersted's and Ampère's discoveries, invented the galvanometer (or "multiplier" as he called it) which consists of a compass needle suspended within a coil of wire. Current flowing in the coil deflects the needle, the amount of deflection indicating the strength of the current. This made available a very sensitive electrical measuring instrument. Sturgeon had also shown that if a bar of iron were placed in a coil of wire the magnetic strength of the coil would be greatly increased. This he called an electromagnet.


Michael Faraday, born of English parents in poor circumstances, became a bookbinder and so was enabled to study books on electricity and chemistry. His desire to become a scientist was so great that he finally induced Sir Humphry Davy to give him a position as his laboratory assistant. He aided Davy in his lectures and experiments and also made a number of experiments himself. As a result of his own research work, he was elected to a Fellowship in the Royal Society in 1824.


Faraday then began a number of electrical experiments in an endeavor to find further relation between electricity and magnetism. Ampère having converted electricity into magnetism, Faraday tried to find out if the reverse were possible. Finally, in the latter part of 1831, he made the experiment of moving a permanent magnet in and out of a coil of wire connected to a galvanometer. This generated electricity in the coil and the galvanometer needle was deflected. He then made a machine consisting of a copper disc mounted on a shaft so that the disc could be rotated between the poles of a permanent horseshoe magnet. A copper brush rubbed against the edge of the disc as it rotated. A galvanometer was connected by wires to this brush and to the shaft so that when the disc was rotated by hand, the current generated deflected the galvanometer needle.


Faraday, being satisfied with pure research work, did not develop his discovery any further, so that it remained for others to make it practicable. It was not, however, until many years later that the dynamo became commercial, and as it is the foundation of the electric light industry, its development is of great importance.




Michael Faraday invented the dynamo, the foundation of the electric light and power industry. The dynamo, however, did not become commercially practicable until about forty years later.


The next year, 1832, Hippolyte Pixii, a Frenchman, going back to Faraday's original experiment of moving a permanent magnet in the neighborhood of a coil of wire, and using Sturgeon's scheme of strengthening the magnetism in the coil of wire by a piece of iron, invented a dynamo that was quite an advance over Faraday's disc machine. It consisted of a permanent horseshoe magnet, the ends of which were rotated about the ends of two coils of wire mounted on a soft iron core. A commutator changed the direction of the alternating current generated so that direct current was obtained. This machine had a very small capacity, about equal to that of the present day standard dry cell used for an electric bell. It was only a laboratory toy, but many of the principles of the present day dynamos were embodied in it. Pixii obtained a U.S. patent on his machine in 1832.




Hippolyte Pixii made a dynamo which was quite an advance. A permanent magnet rotated in the neighborhood of two coils of wire mounted on an iron core, the alternating current generated being rectified by a commutator. This is a photograph of the Patent Office model which is on exhibition at the United States National Museum, Washington, D. C., through whose courtesy the picture is shown.


In 1834, E. M. Clarke, an Englishman, made several dynamos, the principles of which were the same as those of Pixii's except that he rotated the coils of wire alongside the poles of a stationary permanent horseshoe magnet.


Pixii's and Clarke's dynamos produced a pulsating direct current which was made unidirectional by means of a commutator. While this means that they delivered direct current, their voltage (pressure) was pulsating. In 1841 Woolrich devised a machine which had several magnets and double the number of coils, which reduced the pulsations. Wheatstone, in 1845, patented the use of electromagnets in place of permanent magnets.


Brett, in 1848, suggested that the current given by a permanent magnet machine be made to flow through coils surrounding the permanent magnets to further strengthen them and thereby increase the output of the machine.


About this time it was discovered that the iron surrounded by the wire coils became heated due to currents being generated in the iron itself while moving through the magnetic field of the magnets. Such currents are called eddy currents, and in 1849 Pulvermacher proposed that the iron be made into thin sheets to reduce them. All dynamos now have a laminated sheet iron armature core.

In 1851, Sinstenden suggested that the current obtained from a permanent magnet machine be used as a source of excitation to supply current to the field coils of an electro-magnet machine. This scheme, though no permanent magnet machines are now made, is generally used in all large electric power stations, a separate machine being used to supply current for the field coils of the large dynamos.




Dr. Werner Siemens countersunk the armature wires in an iron core, making a cylindrical shaped armature. This revolved between Magnet poles shaped to fit the armature, reducing the air gap and so making a more powerful machine.



In 1855, Hjorth patented a dynamo having both permanent and electro-magnet field poles. The current, first induced in the armature by the permanent magnets, energized the electro-magnet field poles. This, therefore, may be said to be the first "self-excited" electro-magnet machine. It was not commercially used.




This may be called the first "self-excited" machine, having permanent magnet field poles inducing current in the armature which energized the electromagnet fields. It was not used commercially.


Dr. Werner Siemens greatly improved the dynamo by his invention, in 1856, of the shuttle wound armature. The armature coil was countersunk in an iron core so as to make a cylindrical armature which fitted closely between the poles, which were shaped to enclose it. This greatly reduced the air gap between the armature and field poles and thereby greatly increased the number of the magnetic lines of force passing through the armature. This arrangement, in principle, is used in all dynamos made today.


Another interesting dynamo is that designed in 1850, by Nollet, a professor of physics at the Brussels Military School. This dynamo had several rows of permanent magnets mounted radially on a stationary frame, the armature consisting of wire bobbins mounted on a shaft which rotated within the frame. A commutator was used so that direct current could be obtained. A company was organized to supply hydrogen gas enriched with oils for illuminating gas, the hydrogen gas to be made by the decomposition of water with current from this machine.


Nollet died and the company failed. About ten years later it was reorganized as the Alliance Company to exploit the arc lamp, which at that time (1860) had been fairly well developed. Difficulties were experienced with the commutator of the dynamo, so it was removed and collector rings substituted, the machine then delivering alternating current. A trial installation of the arc light was then made in the Dungeness Lighthouse in England, the installation being formally accepted in 1862.


This was the first commercial installation of an electric light, an arc lamp. The Alliance dynamo had a capacity for one arc lamp, which probably consumed about ten amperes at about 45 volts, and as the dynamo was very inefficient, it probably required at least one and a half horse power to drive it.




This machine was designed by Nollet for the commercial manufacture of illuminating gas by decomposing water electrically. This Project failed, but in 1862 the machine was used to supply current to the first commercial use of an electric light, an arc lamp in the Dungeness Lighthouse in England.


Sir Charles Wheatstone is credited with the invention of the first self-excited machine which operated on the principle of utilizing the residual magnetism in the field poles to set up a feeble current in the armature, which, passing through the field coils, gradually increases their strength until they are built up to normal. He built a machine in the summer of 1866, and exhibited it before the Royal Society at a meeting held in February, 1867. A paper describing the machine was read at this meeting. Another paper, forwarded by Dr. Werner Siemens, was also read at the same meeting describing a similar machine invented by him. Wheatstone probably preceded Siemens in this invention.




This was the first self excited dynamo using the residual magnetism in the field poles.


In 1870 Gramme, a Frenchman, made a dynamo having a "ring" wound armature. The armature consisted of a ring shaped core of iron wire which was coated with an insulating compound to reduce the eddy currents. The core was wound with insulated copper wire coils, all connected in series as one single endless coil, each coil being tapped with a wire connected to a commutator bar. The first machine built with electro-magnet fields was made in 1871, and many of these were later built for commercial arc lighting installations.




Its main feature was the "ring" wound armature. Several of these machines were used in commercial service for arc lighting purposes. This dynamo is in the historical collection of the Association of Edison Illuminating Companies in conjunction with the Edison Pioneers by whose courtesy this photograph is reproduced.


Alteneck, an engineer with Siemens, in 1872, invented the "drum" wound armature. The wires were all on the surface of the armature core, being tapped at frequent points for connection with the commutator bars. This method of construction is used in all dynamos now made.




The armature was "drum" wound, that is, the wires were wound on the surface of the armature. This construction is used in all dynamos made to this day.



Davy's Discovery of Electric Light

Sir Humphry Davy was a well known English chemist. About 1802, with the aid of a powerful battery that he had constructed, he made a number of experiments on the chemical effects of electricity. He decomposed a number of substances and discovered several elements, among which were boron, potassium and sodium. He gave several lectures before the Royal Society and incidentally demonstrated that electricity would heat thin strips of metal to a white heat, causing them to oxidize so rapidly in the air that they literally burned up. Platinum, he found, would not oxidize as readily, so that it could be heated to a white heat and give light for a considerable length of time. This was the forerunner of the incandescent lamp, but it was not until 1879 that a lamp suitable for general distribution was invented.


About 1809, Davy also demonstrated the arc light. This he did with a battery of two thousand cells, the terminals of which were connected to two charcoal sticks. A brilliant arch shaped flame was produced when the two charcoal sticks were allowed to touch each other and then pulled apart, the name "arc" being given to this light on account of the shape of the flame.



The First Attempts at Making an Incandescent Lamp

The earliest record of any attempt at making an incandescent lamp was in 1820, when De la Rue made a lamp with a coil of platinum wire for a burner which was enclosed in a piece of glass tubing, the ends of which had brass caps. It was supposed to have had a vacuum, but how this was accomplished is not clear.




In this lamp, the first one on record, a platinum wire operated in vacuum.


Platinum has to operate very close to its melting temperature before it becomes incandescent. At this operating temperature it disintegrates rapidly, so that such a lamp would not last long. The cost of current from the batteries then available made its operating cost prohibitive, so the lamp is of historic interest only.




This lamp is of interest as being the first one on which a patent (British) was granted. The lamp contained powdered charcoal which filled and bridged the gap between two coils of platinum wire mounted in a globe from which the air had been exhausted.


In 1840, Grove gave a lecture before the Royal Society and demonstrated his battery by lighting the auditorium with incandescent electric light. His lamps consisted of a coil of platinum wire fastened to the ends of copper wires, the lower part of which were varnished for insulation. The platinum wire burner was covered by a glass tumbler to protect it from draughts of air, which would otherwise cool it. The open end of the tumbler was set in a glass dish partly filled with water through which the varnished copper wires extended, and which thereby made a seal preventing any draught of air from reaching the burner. The platinum had to be operated very close to its melting point before it became sufficiently incandescent to give any light.




A coiled platinum wire burner was covered by a glass tumbler surrounded by water in a glass dish to protect the burner from draughts of air.


A great deal of current was also required to keep the platinum incandescent as the air in the tumbler tended to cool it by conducting the heat away. It is estimated that the cost of current with Grove's battery was at the rate of several hundred dollars a kilowatt-hour. As a comparison, the present general average retail rate at which current is sold by central station lighting companies is now about eight cents a kilowatt-hour.


The first patent on an incandescent lamp was granted by the British Government in 1841 to Frederick De Moleyns. His lamp was quite novel, consisting of a spherical glass globe in the upper part of which was a glass tube containing powdered charcoal. This tube was open at the bottom and through it ran a platinum wire coiled at the end inside the globe. Another platinum wire extended upward from the bottom of the globe, terminating in a coil whose end was close to that of the first coil. The powdered charcoal in the glass tube filled the two coils of platinum wire, bridging the gap between them. Current flowing from one platinum wire to the other through the bridge of powdered charcoal made the latter incandescent.




The burner was of platinum and iridium operating in air but covered by a globe.


Starr's Contribution to Incandescent Lamp Development

J. W. Starr was an American from Cincinnati, Ohio, who induced George Peabody, the philanthropist, to back him in his research work. He went to England and in 1845 obtained a patent on two incandescent lamps he had invented. This patent was taken out under the name of King, his attorney.


One lamp consisted of a strip of platinum, the active length of which could be adjusted to fit the strength of the battery used so that the burner would operate at the proper temperature. It was covered by a glass globe to protect it from draughts of air.




This lamp had a strip of platinum for a burner whose active length was adjustable to fit the size of battery used. It operated in air but was covered by a globe to protect the burner from draughts.


Starr's other lamp consisted of a carbon rod operating in the vacuum above a column of mercury (Torrecellium vacuum) as in a barometer. A platinum wire was sealed in the upper end of a tubular glass bulb, inside of which was a thin slab of carbon attached to the platinum wire by an iron clamp. The lower end of the carbon slab was attached by another iron clamp to a long copper wire. Fused to the bottom end of the tubular glass bulb was a narrow glass tube, open at the end, and a little over thirty inches in length, into which the copper wire extended. The bulb with its extended glass tube was filled with mercury and set in a dish containing mercury after the fashion of a mercury barometer, so that the mercury ran out of the bulb and came to rest in the tube at about 30 inches above the surface of mercury in the dish.


This lamp, however, was impractical, as it is now known that such a vacuum contains water vapor, and that when the lamp is lighted, the heat will drive gases out of the glass, the carbon rod, iron clamps, etc., which will cause it to blacken rapidly.

Unfortunately, Starr died on board ship, while returning to the United States in the following year (1846). He was only 25 years old.





This consisted of a rod of carbon operating in the vacuum above a column of mercury.


Other Experimental Incandescent Lamps

During the next few years, several inventors tried to make incandescent lamps, even though it was known that their use with current obtained from batteries would be impractical. The dynamo was being improved but was still impractical commercially.


In 1848, W. E. Staite made a lamp having a burner consisting of platinum and iridium operating in the air, but covered by a glass globe to protect it from draughts. It had a thumb screw for a switch, the whole device being mounted on a bracket, the arm of which was to be the return wire.


Edward C. Shepard, in 1850, made a lamp consisting of a weighted charcoal cylinder pressing against a charcoal cone in vacuum. The high resistance contact became incandescent when current flowed through it.




The high resistance contact between a weighted charcoal cylinder pressing against a charcoal cone in vacuum made the charcoal incandescent.


M. J. Roberts, in 1852, made a lamp having a graphite rod operating in vacuum. The open end of the glass globe surrounding the burner was cemented to a metal cap, to which was screwed a pipe containing a stop cock. Through this pipe the air could be exhausted, the stop cock closed and the lamp then mounted on a stand. The graphite rod was held by a clamp at the end of two metal rods, one rod being fastened to the pipe and the other being insulated from but passing through the metal cap. The lamp was not successful because such an arrangement could not maintain a good vacuum for any length of time.


In 1856, De Changy, a French civil engineer, obtained a Belgian patent on a lamp having a coiled platinum wire for the burner which operated in air but was covered by a glass tube to protect it from draughts. It was a portable affair having hooks for terminals, and was intended specially for use in mines. A pair of wires could be fastened to the walls and run throughout the mine; the lamp could be located in different places as desired by simply hooking it to the wires.





This consisted of a graphite rod operating in vacuum.


This had a platinum burner operating in air but covered by a glass tube. It was designed for use in a mine, being so arranged that it could be hooked to wires fastened on the walls throughout the mine and thus be located in the places desired.



Professor Moses G. Farmer, of the Naval Training Station at Newport, Rhode Island, made a lamp in 1859, several of which were used to light the parlor of his home, 11 Pearl Street, Salem, Mass., during July of that year. The lamp consisted simply of a strip of sheet platinum operating in air, the novel feature being that the strip was narrower at the ends than in the middle. This caused it to be more uniformly incandescent throughout its entire length, the higher resistance of the narrowed ends consuming proportionally more electrical energy, and thus offsetting the loss of heat which was conducted away by the terminals of the lamp. He obtained a U.S. patent on this feature many years later (1882).





Prof. Farmer, during July, 1859, lighted the parlor of his home at Salem, Mass., with several of these lamps. The platinum burner was narrowed at its ends so that the entire length became more uniformly incandescent.


Swan's Contributions

Sir Joseph W. Swan, who became one of the foremost incandescent lamp manufacturers in England, made at various times, from 1848 to 1860, a number of experimental lamps. These consisted of carbonized strips and spirals of paper and cardboard, coated with various liquids, which on being heated left a large residue of carbon. These lamps were operated in vacuum, either in a glass bottle having a wide neck closed with a rubber stopper through which the connecting wires passed, or in a glass bell whose rim made a tight fit within the rim of a brass plate through which one insulated connecting wire passed, the plate being used as the other connection. Owing partly to some trace of air being left within the glass container, and partly to the carbons becoming distorted, the lamps soon broke down.



SWAN'S LAMP, 1860.

A strip of carbonized paper was covered by a glass bell fitting tight on a brass plate and operated in vacuum.


The pumps used to produce a vacuum consisted of a plunger operating in a cylinder with valves. This produced a relatively very poor vacuum compared with that now possible. In 1865, Herman Sprengel, by his invention of the mercury vacuum pump, had been able to get a vacuum far superior to any previously attainable. This pump consisted of a long glass tube held vertically, the bottom end being dipped into mercury in a container. The upper end had two branches, one connected to a supply of mercury and the other to the device from which the air was to be exhausted. The mercury, in flowing down the tube, trapped bubbles of air, the weight of the mercury forcing these air bubbles down the tube and out into the outside atmosphere. Thus in time the flow of mercury would exhaust the air from the device.


In 1875, Crookes (afterwards Sir William Crookes), astonished the world by the exhibition of his radiometer and the description of the improved means he employed, in connection, with the Sprengel pump, for obtaining the near approach to a perfect vacuum which the construction of the radiometer demanded. The publication of this paper led Sir Joseph Swan to resume his incandescent lamp experiments.


In 1877, Swan, through a chance advertisement about radiometers, got a young bank clerk, Charles H. Stearn, to assist him in carrying out these experiments. Stearn had been pursuing investigations which required high vacuum and was familiar with the manipulative requirements necessary for obtaining a very high degree of evacuation.


A series of experiments were started by Stearn with carbon conductors of various forms and sizes, which Swan supplied, beginning with the strips and spirals of carbonized paper and cardboard formerly used, and which Swan had firmly fixed in his mind, would be durable when operated to incandescence in a very perfect vacuum. These were mounted in glass bulbs which were exhausted to the highest possible degree by means of the Sprengel pump.


Great difficulty was at first experienced in making firm contact between the ends of the carbon strip and the conducting wires to which it was held. To avoid the manipulative difficulties and to arrive more rapidly at a definite settlement of the question whether and under what conditions a carbon conductor would be durable, the thin strips and spirals were, for the time being, discarded and other forms of carbon conductors were tried. Among the forms used were carbon wires, both straight and bent in an arch, made of the same plastic material commonly used in carbon rods for arc lamps.


Notwithstanding the fact that the lamp bulb had been highly evacuated, the vacuum rapidly deteriorated owing to the evolution of gases from the carbon which took place as soon as current was turned on. This difficulty was overcome by heating the bulb by a flame from the outside and then passing a strong current through the carbon to make it brilliantly incandescent while it was still connected to the exhaust pump. The straight carbon wires were found to buckle and so did not last, but the arch shaped carbon wires gave good results.


When the incandescent lamp became commercially available, Swan invented, early in 1880, the parchmentized thread which, when carbonized, produced a long thin carbon that was used by some manufacturers for many years. He discovered that cotton thread treated with sulphuric acid became agglutinated and lost its fibrous condition, having the appearance and the hardness of catgut when dried. This material could even be planed and scraped down to a fine wire of the most perfect roundness and could be bent into spirals which retained their shape during carbonization.


The difficulty previously experienced in making firm contact between the ends of the fine carbon and the conducting wires was overcome by making enlarged ends on the carbons which were held in tiny silver or copper sockets, similar to that of a crayon holder, and secured with a slip ring. Later on improved means were devised for making good electrical contact by means of a contrivance developed by Swan and Gimingham which consisted in tubulating the ends of the conducting wires, inserting the ends of the carbons in the tubes and causing a deposit of carbon to take place at the junction.




A carbon wire operated in a high vacuum in an all-glass globe.


Russian Incandescent Lamp Inventors

In 1872, Lodyguine, a Russian scientist, made a lamp having a "V" shaped piece of graphite for a burner which operated in nitrogen gas. This was covered by a glass globe fastened to a metallic cap with a gasket to make a tight joint. He installed two hundred of these lamps about the Admiralty Dockyard at St. Petersburg. In 1874 the Russian Academy of Sciences awarded him the Lomonossow Prize of fifty thousand rubles, then worth about $25,000, for his invention. A company was formed with a capitalization of 200,000 rubles to exploit the lamp, but the project soon failed as the lamp was too expensive to operate.




This had a graphite burner operating in nitrogen gas. An experimental installation of two hundred of these lamps was made to light the Admiralty Dockyard at St. Petersburg.


In 1875, Kosloff, another Russian, made a lamp consisting of several graphite rods operating in nitrogen. The rods were so arranged that only one operated at a time and, when it burned out, another was automatically connected in circuit. Konn, also a Russian, invented a lamp in 1875, similar to that of Kosloff, except that the graphite rods operated in vacuum.





This had several graphite rods, one operating at a time. When one burned out, another was automatically connected. The rods operated in nitrogen gas.




This lamp was similar to that of Kosloff's except that the graphite rods operated in vacuum.



The next year, 1876, Bouliguine, another Russian, made a lamp having a long graphite rod, only the upper part of which was in circuit. When this part burned out, a counterweight automatically pushed the rod upward thereby placing a fresh portion of the long rod in circuit. It operated in vacuum.




This had a long graphite rod operating in vacuum. Only the upper part of the rod was in circuit and as this part burned out, the rod was automatically shoved up, thus placing a fresh portion in circuit.


Commercial Introduction of the Arc Lamp

None of these incandescent lamps was practical; they had short lives, were expensive to operate, were unreliable in their operation, and so were not commercially used. By this time, however, the arc lamp was being introduced commercially, the pioneer installation being that of jablochkoff, who lit the boulevards in Paris with his "electric candle." This simple arc lamp consisted of two carbon rods held together side by side and insulated from each other by kaolin. The kaolin vaporized as the carbons were consumed, giving the arc a peculiar color. A complete system was developed by jablochkoff, consisting of an alternating-current generator, having a stationary exterior armature with internally revolving field poles. Alternating current was used to offset the difficulty experienced with the unequal consumption of the carbons on direct current. A series system of distribution was used and, in order to prevent interruption of the circuit should one "candle" go out, several candles were put in each fixture with an automatic device to connect a fresh candle whenever one burned out.


In the United States there were several pioneer arc light systems. The earliest were those of William Wallace, of Ansonia, Connecticut, who became associated with Prof. Moses G. Farmer; Edward Weston, of Newark, New Jersey, the well known maker of electrical measuring instruments; Charles F. Brush, of Cleveland, Ohio; and Prof. Elihu Thomson, who became associated with Edwin J. Houston, and formed the Thomson-Houston Company, a fore runner of the General Electric Company. Thus, in 1877, the arc lamp was commercially established, dynamo electric machines were available, and a demand had arisen for a smaller electric light than the arc lamp.



Subdividing the Electric Light

In this country there were four men who were energetically attacking the problem, popularly called "subdividing the electric light", the arc lamp being the only then known electric light. This phrase was really a misnomer, because the arc lamp was not subdivided into small units, a practical incandescent lamp being the final result of the experiments. These four men were: William E. Sawyer, Prof. Moses G. Farmer, Hiram S. Maxim, and Thomas A. Edison.


Sawyer became associated with Albon Man, his patent attorney, who gave him financial assistance. The Sawyer-Man Electric Company was organized and several lamps were developed. They all consisted of a piece of graphite operating in nitrogen, covered by a glass globe cemented to a metal holder.


Heavy fluted copper wires were used to make connections with the burner through the holder, in order to radiate the heat and thereby maintain a cool joint between the glass globe and holder. The lamps were designed so that they could be renewed by opening the joint and putting in a fresh burner. The company failed, but was later reorganized after Edison's invention of a practical lamp. This company was a forerunner of the present Westinghouse Lamp Company.


Farmer made a lamp consisting of a graphite rod which also operated in nitrogen gas. It was covered by a glass bulb having a rubber stopper through which copper rods connecting with the burner were passed. A tube was put in the rubber stopper through which the air was exhausted and nitrogen gas put in.





This was one of several developed, all having a graphite burner operating in nitrogen gas. The heavy fluted copper wires were used to radiate the heat and thus maintain a cool joint between the glass cover and metal holder.




This also had a graphite rod operating in nitrogen gas. This lamp is on exhibit at the United States National Museum at Washington, D.C., through whose courtesy this photograph is shown.



Maxim, well known for his later invention of the rapid fire gun, made two lamps. One consisted of a piece of sheet platinum operating in air. The main feature of this lamp was that when the platinum, held at the top by an adjustable bolt and nut, became too hot and dangerously near its melting temperature it would expand sufficiently to make contact with a wire which short circuited the burner. This shunted the current from the platinum burner, allowing it to cool for a fraction of a second so that it shrunk, opening the short circuit and allowing current to flow again through the burner. The other lamp consisted of a graphite rod operating in a rarefied hydrocarbon vapor and protected from excessive current by an electromagnet which short circuited the graphite burner.




A graphite rod operated in a rarefied hydrocarbon vapor. An electro-magnet short circuited the burner when the current became too strong. This lamp is also on exhibit at the United States National Museum, through whose courtesy this photograph is shown.