LIGHT WITHOUT HEAT.

Otago Daily Times, Issue 9391, 2 April 1892, Page 5 (Supplement)

LIGHT WITHOUT HEAT.

A STRIKING BXPEBIJtENT,

Mr Nikola Tesla, a young American electrician, has invented a new dynamo from which alternative currents of th.c highest frequency and greatest potential can be obtained. One of these machines has been exhibited at the Royal Institution, London. It carries nearly 400 electro-magnets, driven at some 2000 revolutions per minute, and supplies a current alternating 20,000 times or more per second. Currents of still higher frequency and potential are obtained bypassing the spark or disruptive discharge from a battery of Leydeu jars through the primary circuit of an induction £oil. Thanks to the high potential and oscillatory character of the Leyden jar discharge currents haviug a frequency of one or two million times a second, and of enormously high potential, can be had in this way from small induction coils. The most striking property of the current :so obtained is its power to traverse the air. Everybody knows ;hat the current from an ordinary induction coil will leap across the vacuum—the inside of a Geissler tube, for example—causing a glow of greater or less brilliancy. Mr VTesla's current, however, possesses force enough to make its way through the air. The most striking experiment shown consisted in joining two sheets of tinfoil, one over the lecturer's head, the other on the table, to the poles of his generator. Thu space between these two sheets immediately electrified, and a long vacuum tube waved about in it, without attachment to any conductor whatever, glowing in the darkness like a flaming sword. This experiment was intended to illustrate the possibility of rendering an entire room so electric, by plates in the ceiling or under the floor, that vacuum bulbsi placed anywhere within it would yield a light. It is a remarkable fact that currents of these extremely high potentials appear to be absolutely without effect upon the human organism. Taking an iron bar in one hand and a vacuum tube in the other, the lecturer made his body a portion of the circuit by placing the point of the bar upon a terminal, emitting sparks several inches long. The vacuum tube glowed brilliantly, while the lecturer remained wholly unaffected. Such an experiment could not he attempted with the currents to which we have been accustomed. There seems, therefore, to be some possibility of a new mode of artificial illumination—a light bright like that of the sun, but, unlike it, entirely devoid of heat.

— The French description of the English climate is that there are eight' mouths of winter and four of bad weather,