Page:Popular Science Monthly Volume 14.djvu/247

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When scientific men shook their heads and said it would not do—that there were limits in the case which forbade the expected progress, and that zinc burned in batteries could not compete with coal burned under the boiler—the replies were ready. First, did not Dr. Lardner say that steam-navigation across the Atlantic was impracticable? Second, was there any limit to that power of which the lightningflash was an example? Third, if the electro-magnetic engine was weak, was it not also new, and who would presume to put restrictions upon man's inventive genius, especially when the main thing was already achieved, and nothing remained but to work out the minor improvements? The new motor, however, could not be made to work, and so hopes were crushed, investments lost, and the excitement died away.

The difficulty with the electric light, which has hitherto defied resolution, notwithstanding the efforts of experimenters for a generation, is that it can only be realized under an intensity of action that becomes far too expensive for common use, where only a small amount of illumination is required. A brilliant light can be got from the electric current by the incandescence of carbon or metallic particles, which will flood great spaces with a vivid illumination much cheaper than can be done in any other way, but nobody has yet been able to divide and distribute this intense light so as to utilize it in small amounts wherever wanted, at a cost that can compete with the ordinary sources of illumination. A well-informed writer in a late issue of the New York Sun gives the following instructive presentation of the present aspect of the subject:

"I judge that the panic in gas-stocks, which has been produced in great part by the broad claims of Mr. Edison to the discovery of a practicable method of subdividing the electric light, is, to say the least, premature. Mr. Edison is now experimenting with his light, and at latest accounts had not solved all the problems involved. The field in which he is laboring is an entirely new one to him, as the science of magneto- or dynamo-electricity is far different from that of telegraphy or electro-magnetism. There are problems involved, especially in the subdivision of the light, which are far greater than any embodied in any previous invention or improvement of Mr. Edison. The scientific world has been laboring at it almost constantly since King's invention in 1848. In 1858 M. Jobart, of Paris, made some very startling claims, which were almost exactly the same as those made by Edison, but continued experiment exposed their fallacy.

"The principal difficulty to be overcome is the lack of economy in any method of producing light by electricity, except by the voltaic arc between carbon-points, and as Mr. Edison disclaims this method, and limits himself to the plan of incandescence, he will find his path beset with difficulties in this direction. This is shown by the well known fact that an electrical current of a given strength will yield about ten times as much light when used to produce the voltaic arc between carbon-points as it could by being passed through a piece of platinum, so as to raise it to a white heat and give the light. In some experiments recently made in Paris by M. Fontaine, it was found that a powerful battery of forty-eight elements would produce in one lamp a light by incandescence equal to forty burners; but that, when the same current was used in two lamps, the light in each was only three to five burners, and, when divided between three lamps, only one-quarter burner in each. Further subdivision resulted in a total extinction of the light. A similar result was reached whether the lamps were placed in series in the same circuit or in derived circuits. In using a dynamo-electric machine in place of a battery as the source of the electricity, the same difficulty would present itself, with this additional one, that whereas the electro-motive force of a battery remains constant under all changes of resistance, that of a machine does not, but decreases as the resistance increases.

"The writer has thoroughly investigated the subject of electric light as an economical subtitute for gas, and is entirely familiar with all that has been accomplished here or abroad in this direction. Abroad, by means of the Gramme machine and the Jablochkoff candle, sixteen lights of 700-candle power each are produced from one machine, ab-