Page:Popular Science Monthly Volume 49.djvu/233

Rh impenetrable, that Franklin less than five generations ago should detect that lightning and electricity are one, and that only in our day at the hands of Hertz has it been demonstrated that the electric pulse differs only from the wave of heat or light in being longer. This discovery of Hertz was long ago foreshadowed in the observation that heat can have electric origin. One of the first fruits of electrical study was the finding that some metals transmit electricity better than others, and that the efficacy of a conductor depends in part on its size. When a conducting wire was reduced to extreme tenuity, the resistance to the current's passage, with striking resemblance to common friction, expressed itself as vivid heat. The miner and the gunner at once saw their opportunity to use electricity to touch off their fuses and to explode at the same instant, with an effect before impossible, a round of separate charges.

Copying the methods of the miner, the mechanic and the chemist very often find electric heat the most advantageous they can employ. When the broken blade of a propeller is to be repaired, the electric welder can be taken to its work instead of the work having to go to a stationary welder. When electric heat is carried into a crucible through almost impenetrable walls of gypsum, it enters the very heart of its task without the offense and waste of flame. Thus to-day is flame face to face with a supplanter in the shape of its long undetected twin. Until this generation flame alone was the source not only of heat, but of the beam of candle, lamp, and gas jet. To-day myriads of electric bulbs are aglow without flame—indeed, just because combustion is rendered impossible by the rigid exclusion of air. As these incandescent lamps were long ago prophesied in the miner's electric fuse, so also has the first simple process of the electroplater led up to an art incomparably more important. To-day not surfaces merely, but large masses, chiefly of statuary, are built in cool tanks by electricity. Let the current become cheaper still, and the founder may find the remainder of his business transferred to this formidable rival, the warping heats of sand molds banished, the scorching temperature of crucible and ladle a reminiscence. The same fate may be in store for the smelting furnace. Already vast quantities of copper are refined electrolytically, and an auspicious beginning has been made in using electricity for the whole process of parting metal from ore. Thus methods which commenced in dismissing flame end boldly by eliminating heat itself. This usurping electricity, it may be said, usually finds its source, after all, in fire under a steam boiler. True, but mark the harnessing of Niagara, of the Lachine Rapids near Montreal, of a thousand streams elsewhere. In the years of the near future motive power of Nature's giving is to be wasted less and less, and per