chapter 29-40._

ELECTRICITY: A. D. 1831-1872. Dynamo Electrical Machines, and Electric Motors.

"The discovery of induction by Faraday, in 1831, gave rise to the construction of magneto-electro machines. The first of such machines that was ever made was probably a machine that never came into practical use, the description of which was given in a letter, signed 'P. M.,' and directed to Faraday, published in the Philosophical Magazine of 2nd August, 1832. We learn from this description that the essential parts of this machine were six horse-shoe magnets attached to a disc, which rotated in front of six coils of wire wound on bobbins." Sept. 3rd, 1832, Pixii constructed a machine in which a single horse-shoe magnet was made to rotate before two soft iron cores, wound with wire. In this machine he introduced the commutator, an essential element in all modern continuous current machines. "Almost at the same time, Ritchie, Saxton, and Clarke constructed similar machines. Clarke's is the best known, and is still popular in the small and portable 'medical' machines so commonly sold. ... A larger machine [was] constructed by Stöhrer (1843), on the same plan as Clarke's, but with six coils instead of two, and three compound magnets instead of one. ... The machines, constructed by Nollet (1849) and Shepard (1856) had still more magnets and coils. Shepard's machine was modified by Van Malderen, and was called the Alliance machine. ... Dr. Werner Siemens, while considering how the inducing effect of the magnet can be most thoroughly utilised, and how to arrange the coils in the most efficient manner for this purpose, was led in 1857 to devise the cylindrical armature. ... Sinsteden in 1851 pointed out that the current of the generator may itself be utilised to excite the magnetism of the field magnets. ... Wilde [in 1863] carried out this suggestion by using a small steel permanent magnet and larger electro magnets. ... The next great improvement of these machines arose from the discovery of what may be called the dynamo-electric principle. This principle may be stated as follows:--For the generation of currents by magneto-electric induction it is not necessary that the machine should be furnished with permanent magnets; the residual or temporary magnetism of soft iron quickly rotating is sufficient for the purpose. ... In 1867 the principle was clearly enunciated and used simultaneously, but independently, by Siemens and by Wheatstone. ... It was in February, 1867, that Dr. C. W. Siemens' classical paper on the conversion of dynamical into electrical energy without the aid of permanent magnetism was read before the Royal Society. Strangely enough, the discovery of the same principle was enunciated at the same meeting of the Society by Sir Charles Wheatstone. ... The starting-point of a great improvement in dynamo-electric machines, was the discovery by Pacinotti of the ring armature ... in 1860. ... Gramme, in 1871, modified the ring armature, and constructed the first machine, in which he made use of the Gramme ring and the dynamic principle. In 1872, Hefner-Alteneck, of the firm of Siemens and Halske, constructed a machine in which the Gramme ring is replaced by a drum armature, that is to say, by a cylinder round which wire is wound. ... Either the Pacinotti-Gramme ring armature, or the Hefner-Alteneck drum armature, is now adopted by nearly all constructors of dynamo-electric machines, the parts varying of course in minor details." The history of the dynamo since has been one of a gradual perfection of parts, resulting in the production of a great number of types, which can not here even be mentioned.

_A. R. von Urbanitzky, Electricity in the Service of Man, pages 227-242._

_S. P. Thompson, Dynamo Electrical Machines._

ELECTRICITY: Electric Motors.

It has been known for forty years that every form of electric motor which operated on the principle of mutual mechanical force between a magnet and a conducting wire or coil could also be made to act as a generator of induced currents by the reverse operation of producing the motion mechanically. And when, starting from the researches of Siemens, Wilde, Nollet, Holmes and Gramme, the modern forms of magneto-electric and dynamo-electric machines began to come into commercial use, it was discovered that any one of the modern machines designed as a generator of currents constituted a far more efficient electric motor than any of the previous forms which had been designed specially as motors. {775} It required no new discovery of the law of reversibility to enable the electrician to understand this; but to convince the world required actual experiment."

_A. Guillemin, Electricity and Magnetism, part 2, chapter 10, section 3._

ELECTRICITY: A. D. 1835-1889. The Electric Railway.

"Thomas Davenport, a poor blacksmith of Brandon, Vt., constructed what might be termed the first electric railway. The invention was crude and of little practical value, but the idea was there. In 1835 he exhibited in Springfield, Massachusetts, a small model electric engine running upon a circular track, the circuit being furnished by primary batteries carried in the car. Three years later, Robert Davidson, of Aberdeen, Scotland, began his experiments in this direction. ... He constructed quite a powerful motor, which was mounted upon a truck. Forty battery cells, carried on the car, furnished power to propel the motor. The battery elements were composed of amalgamated zinc and iron plates, the exciting liquid being dilute sulphuric acid. This locomotive was run successfully on several steam railroads in Scotland, the speed attained was four miles an hour, but this machine was afterwards destroyed by some malicious person or persons while it was being taken home to Aberdeen. In 1849 Moses Farmer exhibited an electric engine which drew a small car containing two persons. In 1851, Dr. Charles Grafton Page, of Salem, Massachusetts, perfected an electric engine of considerable power. On April 29 of that year the engine was attached to a car and a trip was made from Washington to Bladensburg, over the Baltimore and Ohio Railroad track. The highest speed attained was nineteen miles an hour. The electric power was furnished by one hundred Grove cells carried on the engine. ... The same year, Thomas Hall, of Boston, Mass., built a small electric locomotive called the Volta. The current was furnished by two Grove battery cells which were conducted to the rails, thence through the wheels of the locomotive to the motor. This was the first instance of the current being supplied to the motor on a locomotive from a stationary source. It was exhibited at the Charitable Mechanics fair by him in 1860. ... In 1879, Messrs. Siemen and Halske, of Berlin, constructed and operated an electric railway at the Industrial Exposition. A third rail placed in the centre of the two outer rails, supplied the current, which was taken up into the motor through a sliding contact under the locomotive. ... In 1880 Thomas A. Edison constructed an experimental road near his laboratory in Menlo Park, N. J. The power from the locomotive was transferred to the car by belts running to and from the shafts of each. The current was taken from and returned through the rails. Early in the year of 1881 the Lichterfelde, Germany, electric railway was put into operation. It is a third rail system and is still running at the present time. This may be said to be the first commercial electric railway constructed. In 1883 the Daft Electric Company equipped and operated quite successfully an electric system on the Saratoga & Mt. McGregor Railroad, at Saratoga, N. Y." During the next five or six years numerous electric railroads, more or less experimental, were built." October 31, 1888, the Council Bluffs & Omaha Railway and Bridge Company was first operated by electricity, they using the Thomson-Houston system. The same year the Thomson-Houston Co. equipped the Highland Division of the Lynn & Boston Horse Railway at Lynn, Massachusetts. Horse railways now began to be equipped with electricity all over the world, and especially in the United States. In February, 1889, the Thomson-Houston Electric Co. had equipped the line from Bowdoin Square, Boston, to Harvard Square, Cambridge, of the West End Railway with electricity and operated twenty cars, since which time it has increased its electrical apparatus, until now it is the largest electric railway line in the world."

_E. Trevert, Electric Railway Engineering, appendix A._

ELECTRICITY: A. D. 1841-1880. The Incandescent Electric Light.

"While the arc lamp is well adapted for lighting large areas requiring a powerful, diffused light, similar to sunlight, and hence is suitable for outdoor illumination, and for workshops, stores, public buildings, and factories, especially those where colored fabrics are produced, its use in ordinary dwellings, or for a desk light in offices, is impractical, a softer, steadier, and more economical light being required. Various attempts to modify the arc-light by combining it with the incandescent were made in the earlier stages of electric lighting. ... The first strictly incandescent lamp was invented in 1841 by Frederick de Molyens of Cheltenham, England, and was constructed on the simple principle of the incandescence produced by the high resistance of a platinum wire to the passage of the electric current. In 1849 Petrie employed iridium for the same purpose, also alloys of iridium and platinum, and iridium and carbon. In 1845 J. W. Starr of Cincinnati first proposed the use of carbon, and, associated with King, his English agent, produced, through the financial aid of the philanthropist Peabody, an incandescent lamp. ... In all these early experiments, the battery was the source of electric supply; and the comparatively small current required for the incandescent light as compared with that required for the arc light, was an argument in favor of the former. ... Still, no substantial progress was made with either system till the invention of the dynamo resulted in the practical development of both systems, that of the incandescent following that of the arc. Among the first to make incandescent lighting a practical success were Sawyer and Man of New York, and Edison. For a long time, Edison experimented with platinum, using fine platinum wire coiled into a spiral, so as to concentrate the heat, and produce incandescence; the same current producing only a red heat when the wire, whether of platinum or other metal, is stretched out. ... Failing to obtain satisfactory results from platinum, Edison turned his attention to carbon, the superiority of which as an incandescent illuminant had already been demonstrated; but its rapid consumption, as shown by the Reynier and similar lamps, being unfavorable to its use as compared with the durability of platinum and iridium, the problem was, to secure the superior illumination of the carbon, and reduce or prevent its consumption. As this consumption was due chiefly to oxidation, it was questionable whether the superior illumination were not due to the same cause, and whether, if the carbon were inclosed in a glass globe, from which oxygen was eliminated, the same illumination could be obtained. {776} Another difficulty of equal magnitude was to obtain a sufficiently perfect vacuum, and maintain it in a hermetically sealed globe inclosing the carbon, and at the same time maintain electric connection with the generator through the glass by a metal conductor, subject to expansion and contraction different from that of the glass, by the change of temperature due to the passage of the electric current. Sawyer and Man attempted to solve this problem by filling the globe with nitrogen, thus preventing combustion by eliminating the oxygen. ... The results obtained by this method, which at one time attracted a great deal of attention, were not sufficiently satisfactory to become practical; and Edison and others gave their preference to the vacuum method, and sought to overcome the difficulties connected with it. The invention of the mercurial air pump, with its subsequent improvements, made it possible to obtain a sufficiently perfect vacuum, and the difficulty of introducing the current into the interior of the globe was overcome by imbedding a fine platinum wire in the glass, connecting the inclosed carbon with the external circuit; the expansion and contraction of the platinum not differing sufficiently from that of the glass, in so fine a wire, as to impair the vacuum. ... The carbons made by Edison under his first patent in 1879, were obtained from brown paper or cardboard. ... They were very fragile and short-lived, and consequently were soon abandoned. In 1880 he patented the process which, with some modifications, he still adheres to. In this process he uses filaments of bamboo, which are taken from the interior, fibrous portion of the plant."

_P. Atkinson, Elements of Electric Lighting,