Scientific American Supplement, No. 315, January 14, 1882 eBook

This eBook from the Gutenberg Project consists of approximately 129 pages of information about Scientific American Supplement, No. 315, January 14, 1882.

Scientific American Supplement, No. 315, January 14, 1882 eBook

This eBook from the Gutenberg Project consists of approximately 129 pages of information about Scientific American Supplement, No. 315, January 14, 1882.

The limited time at my disposal, and a keen consideration for your feelings, will not permit me to follow the long series of struggles between mind and matter immediately following Jablochkoff’s brilliant invention; suffice it to say, that the few years just passed have yielded beyond comparison the most marvelous results in the scientific history of the world, and it will be superfluous to remind you that a great part of this has undoubtedly been due to the researches made in an effort to reduce electric lighting to a commercial basis.  To say that this has been fully accomplished is but to repeat a well known fact; and in proof of this I quote a high scientific authority by stating that a result so high as 4,000 candles evolved for 40,000 foot-pounds absorbed has recently been obtained—­an efficiency six or seven times greater than the record of six years ago.  In accepting this statement we must not lose sight of the extreme probability that such effects were evolved under conditions rarely if ever found in common practice.  Of course, I now refer to the arc system.  The volume of light so generated is incomparably greater than by any other known method, though in subdivision the limit is sooner reached.

Mr. Hawkesworth—­Let me ask you a question, please.  Supposing that it required a one-horse power to produce an arc light of, say, 2,000 candles, would it be possible to produce ten arc lights of 200 candles each?

Mr. Daft—­No, sir; I will tell you why.  It would, if no other element than the simple resistance of the arcs opposed the passage of a current; then a machine that would produce an inch arc in one light, if placed on a circuit of sixteen lamps would give to each an arc one-sixteenth of an inch long naturally; but another difficulty here presents itself in the shape of a resisting impulse of considerable electromotive force in the opposite direction, apparently caused by the intense polarity of the two terminals.  The resistance of the arc itself varies much according to the volume of current used being usually small with a large quantity of current, and greater with a current of tension; but this opposing element is always found, and appears to be the only real obstacle in the way of infinite subdivision.

Almost every objection which human ingenuity could suggest has been urged against lighting by electricity, but fortunately electricians have been able in most cases either to meet the difficulty or prove it groundless.

In this connection I am led to speak of the common idea that electric light is injurious to the eyes, first, because of its unsteady character, and secondly, by reason of the great excess of the more refrangible rays.  Both objections undoubtedly hold good where the alleged causes exist; but we can now show you a light which is certainly as steady as the ordinary gaslight—­indeed more steady in an apartment where even feeble currents of air circulate; and I am sure you will readily acknowledge that the latter objection is disposed of when I assure you that our light presents the only example with which I am acquainted of an exact artificial reproduction of the solar light, as shown by decomposition.  The two spectra, placed side by side, show in the most conclusive manner the identity in composition of our light with that of the sun.

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Scientific American Supplement, No. 315, January 14, 1882 from Project Gutenberg. Public domain.