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The marvellously cheap "water-gas" which is made through a jet of steam impinging upon incandescent carbons or upon other suitable glowing hot materials will, no doubt, for a long time command the market after the date at which coal-gas for the generation of power has been partially superseded.
The zinc plates of these elements were each of them 32 inches square, and formed altogether a surface of 80 square meters. It was with this powerful battery that Davy, in 1810, performed the experiment on the voltaic arc before the members of the Royal Institution. The carbons employed were rods of charcoal, and were rapidly used up in burning in the air.
In some places there are supervisors who give talks and discuss the actual letters, good ones and bad, which have been written. They go over the carbons and hold conferences with the correspondents who need help.
Some of these lights were already in use for large indoor spaces, although the size of the unit, the deadly pressure of the current, and the sputtering sparks from the carbons made them highly objectionable for such purposes.
The president of a bank which has branches in London and Paris and other big foreign cities used every now and then to stop the boy who was carrying a basket of carbons to the file clerk and look them over. If he found a letter he did not like, or one that he did like a great deal, he sent for the person who wrote it and talked with him. It was not necessary for him to go over the letters often.
We might, then, perhaps explain the different effects of the wear of the carbons serving as rheophores, according as the currents are continuous or alternating, by the different calorific effects produced on these carbons, and by the effects of electric conveyance which are a consequence of the passage of the current through the arc.
"Yes; some of the companies put gas down lower than they could manufacture it, in order to hold their customers at a time when people almost believed that Edison's light would prove a success." "But it was a success. It proved an excellent light, displayed a neat lamp, and gave no ill effects upon either the atmosphere or the eyes; and the perfect carbons showed a surprising endurance.
Others before him had attacked the problem of electric lighting, but lack of suitable carbons stood in the way of their success. Brush overcame the chief difficulties and made several lamps to burn in series from one dynamo. The first Brush lights used for street illumination were erected in Cleveland, Ohio, and soon the use of arc lights became general.
Kennedy was speaking rapidly and was careful not to pause long enough to give Prescott an opportunity to interrupt him. "These ultra-violet rays," he continued, "are always present in an electric arc light though not to a great degree unless the carbons have metal cores.
This black Lethe is the London smoke and fog, which has left a dark deposit over all the building, except the upper and more exposed parts, where the original silvery whiteness of the stone shows through, the effect of the whole thus being like one of those graphic Rembrandt photographs or carbons, the prominences in a strong light, and the rest in deepest shadow.
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