Discoveries and Inventions of the Nineteenth Century

to insure perfect confidence in the regular exhibition of the electric light, this light can be doubled in intensity during such evenings as the atmosphere is found to be so thick as to impair its efficiency. This double power would be obtained at the trifling additional cost of coals and carbons consumed during the time this increased power may be found to be necessary; this additional cost I estimate at 4d. per hour. With the arrangement proposed 516for the electric light, I consider this powerful illuminant, if manipulated by 517careful attendants, perfectly reliable: in proof of this I may state that the electric light at the Souter Point Lighthouse, on the coast of Durham, has now been exhibited two years and a half, and the light has never been known to fail for one minute.” Fig. 278.—Gramme Machine, with Eight Vertical Electro-magnets. Fig. 279.—Gramme Machine, with Horizontal Electro-magnets. Fig. 278 represents one of the light-producing machines. The electro-magnets are excited by a portion of the currents they themselves produce, they retaining sufficient residual magnetism to develop the currents. There is a pair of current-collectors on each side. This machine weighs 1,540 lbs., its height is 3 ft., and width 2 ft. It will produce a light having the intensity of 500 Carcel lamps, which may be doubled by increasing the speed. Fig. 279 is another form which is also adapted for illuminating purposes, and, when made with fewer coils, for electrotyping purposes also. There are in this also two sets of current-collectors, and by means of a connecting cylinder (seen at the base of the machine) the currents can be combined for quantity and for tension as may be required. This machine is only about 2 ft. square, and it produces a light equal to 200 burners; but this may be increased, as the following table shows: 518 Number of revolutions per minute. Intensity of light in Carcel Lamps. Remarks. 650 77 No heating and no sparks. 850 125 No heating and no sparks. 880 150 No heating and no sparks. 900 200 No heating and no sparks. 935 250 A little heat, no sparks. 1,025 290 Heat and sparks. The value of M. Gramme’s invention for electro-plating is proved by the fact of its adoption by Messrs. Christofle of Paris, whose electro-plating establishment is one of the largest in the world. This firm has no fewer than fourteen of these machines at work, and each is capable of depositing 74 ozs. of silver per hour. There is little doubt that the electric current will now soon be employed for reducing metals. Thus fine copper, which is worth 3s. or 4s. per lb., may perhaps be obtained at about the cost of ordinary copper; potassium, sodium, and aluminium at less than half their present price; and magnesium, calcium, and other rare metals at prices which will bring them into commercial use. The machine shown in Fig. 280 is intended for electro-plating and for general purposes: it supplies the means of readily and cheaply plating with copper, or with any other metal, such articles as steam pipes, boiler tubes, ship plates, guns, bolts, nails, marine engines, machinery, culinary vessels, cisterns, &c. The advantage of protecting iron or other material from corroding agents is obvious; and as iron coated with copper is available not only for useful, but also for artistic, purposes, as a cheap substitute for bronze, this invention will doubtless lead to a greatly extended application of bronzed iron in buildings and ornamental structures. The machine well illustrates how mechanical work may be changed into electricity, and electricity caused to do work. The power required to drive the machine at a given speed is much less when no current is being drawn from it, than when the current is flowing. If the current from one machine is sent through the armature of another, the latter revolves, and may be made to do work. Thus power may be conveyed to a distance by electricity, with only the loss caused by the resistance of the conducting wires. If, when two machines are thus connected, the direction of rotation in the first one be suddenly reversed, the armature of the second will almost immediately stop, and then resume its motion in the opposite direction. A very interesting experiment can be performed when the circuit connecting the two machines is made to include a certain length of platinum wire. When both machines are in motion, the platinum exhibits no heating effects; but if the second machine be stopped by an assistant while the rotation of the first is continued, the wire is raised to a red heat. In this way it is shown that motion, electricity, and heat are related to each other, and are mutually convertible; for on the stopping of the second machine, the electricity being no longer used up, so to speak, in producing motion, has its power transformed into heat. The Gramme machine has also been ingeniously employed for railway brakes on some of the Belgian lines; and it is applicable to telegraphy, where the cost of zinc, acids, batteries, &c., is a considerable item. It is 519impossible to predict the many applications for manufacturing purposes which will be made of electricity, now a cheap, reliable, and convenient mode has been discovered of producing currents of any required strength. Though by no means the first or only machine by which mechanical force can be converted into dynamical electricity, it shows an immense advance on any former one in the regularity of the action, and in the capability of being driven at a very high rate of speed without the inconvenient accompaniments of the heating of the conductors and destructive sparks at the movable contacts. There can be no doubt of the importance of this machine for use in lighthouses, and for metallurgical and chemical purposes, and the inventor believes the time will come when all large ocean-going vessels will carry an electric light at the masthead. The light would be sufficiently powerful to show rocks or land five or six miles ahead, and an additional safeguard of incalculable value would be thus provided for those “that go down to the sea in ships, that do business in great waters.” Fig. 280. ELECTRIC LIGHTING AND ELECTRIC POWER. Fig. 280a.—The Alliance Machine. It was mentioned in the last section that the introduction of so convenient and reliable a means of producing electrical currents as the Gramme machine, would cause electricity to be largely applied for illuminating and other purposes. The Gramme machine was first made in 1870, and it attracted much attention, as the principle of combining the currents was quite different from that used in previous magneto-electric 520machines. In fact, the Gramme machine yielded quite unexpected results, and the principle employed in it opened a new field. The development that has taken place in the applications of electricity within the twenty years since 1870 has been truly marvellous. The electric light appears to have been first used in lighthouses about 1862, and the machines by which the current was produced were, in principle, combinations of a great number of Clarke’s machines (see page 509). One such machine was invented by Mr. Holmes, and was used for the illumination of the South Foreland Lighthouse in 1862. Another similar form of still earlier invention had been set up in Paris as early as 1855,—not, indeed, for the purposes of illumination, but for a project which failed. Its arrangement had been originally suggested by a Belgian physicist in 1849; and the machine of 1855, having received certain improvements, afterwards became very well known by the name of the Alliance Company’s machine, or simply the Alliance machine. It is represented in its improved form in Fig. 280a. Here ranges of steel horse-shoe magnets will be observed, each magnet weighing about 40 lbs. and made of six plates of tempered steel, held together with screws. Each of the eight rows of magnets contains seven, and thus sixteen poles are presented at uniform distances, arranged in circles. Carried on the central axle are six discs, which revolve between the circles of sixteen poles, and on the circumference of each disc are sixteen equidistant bobbins or coils of insulated wire, so that the whole of the sixteen coils are opposite to the sixteen poles at the same moment. The extremities of the wires at the coils are connected with proper 521adjustments for gathering up the currents, and by means of these the coils may be arranged either for tension or for quantity, like the elements of a battery (page 494). Fig. 280b.—Wilde’s Machine. Wilde’s machine, which has been mentioned in page 511, is shown in fig. 280b. It will be observed that this consists of a small machine, M, with permanent steel magnets, and the current from these circulates through the coils of the electro magnets, A B. The arrangement of the armatures, bobbin, commutators, etc., is the same in both cases. But as a speed of 2,500 revolutions per minute was needed, it was necessary to 522keep the bearings, T T, from heating by causing cold water to circulate through them. Mr. Ladd arranged a machine on the same principle as Wilde’s, by suppressing the permanent magnets, but availing himself of the residual magnetism of the iron core to bring about the induction. A machine of this kind was shown at the Paris Exhibition of 1867, and people were quite astonished to see electrical power capable of producing a brilliant light developed by a small machine 2 ft. long, 1 ft. wide, and 9 in. high. But the great velocity of rotation, and the consequent heating of the bearings, left much to be desired before a really practical machine could be produced. Fig. 280c.—Siemens’ Dynamo. In the newest Siemens’ machine, represented in fig. 280c, the Gramme principle is made use of, as the revolving coil is of large diameter, and it consists of a copper cylinder, on which are wound a number of juxtaposed coils like those of a galvanometer. The revolving cylinder is surrounded by the poles of a system of electro-magnets excited by the whole of the induced current being passed through their coils. In a paper describing this machine, Siemens first made use of the term “dynamo-electric machine,” and this expression, contracted to the single word DYNAMO, has since been universally employed to designate machines of this kind. The modifications in the forms and arrangements of the different dynamos that have been invented in late years are endless, and every week patents are granted for further improvements and fresh combinations of the parts. It would be quite beyond the scope of this work to enumerate all the forms of the dynamo that have been favourably spoken of; but we shall content ourselves by adding a drawing of the Brush dynamo (Fig. 280d), which has been so largely used for electric lighting in the United States. In this dynamo we have a Gramme ring, but the number of coils on it is reduced 523to eight, the intervals being filled up with pieces of iron, and the ring revolves in a vertical plane between the poles of two double oblong electro-magnets, which are arranged with poles of the same name opposite to each other. The commutators shown in the nearer part convert the alternately reversed currents generated in the coils into a direct continuous one. They are formed with bundles of wires, as in the Gramme machine. Fig. 280d.—The Brush Dynamo. Fig. 280e.—Siemens’ Regulator. But the providing of a cheap and efficient source of current electricity, although an absolutely necessary step, would not have been capable of bringing about the present development of electric lighting, unless the appliances by which the current is made to manifest itself as light had not also been brought nearly to perfection. The conditions required to maintain a steady light from a current of electricity passing between carbon points have been already explained on page 497, and a representation of Dubosc’s electric lantern and regulator is shown. The regulator systems that have been invented since it became obvious that the light of the electric arc admitted of practical application on the large scale are very numerous. The earlier forms of regulator, which were used only for scientific purposes—such as lantern projections on screens, experiments