world to carry with them full knowledge of the instrument which Mr. Edison hopes to perfect. Thus a distinguished scientist like Mr. Edison himself, upon reaching his spirit abode, would be perfectly familiar with the qualities of the instrument and would know what forces were necessary to set in motion to operate the recording apparatus of the machine.     The wonderful new invention—as yet unnamed—which enables us to see in the dark, to detect by their bodily heat alone the presence of bodies or objects which are entirely invisible to the naked eyes, was developed by Samuel O. Hoffman, formerly of the Science and Research Division of the United States Army. It rendered effective service during the closing weeks of the great war, and if it had been perfected earlier it would undoubtedly have played a leading part in the defeat of Germany. A means of locating troops, trenches, artillery, etc., available to one side alone, would have given that side a preponderant advantage in the war.     As has long been known, every object emits a large quantity of radiation, only a small part of which affects the eye. This radiation is the ordinary dark heat, such as is felt on bringing the cold hand an inch or so in front of the face. While of the same general nature as light, it has quite different properties. Hardly any substances are transparent to it, rock salt being the only one easily obtainable. Glass is particularly opaque, so that ordinary optical instruments are useless. However, sharp images can be easily formed by using concave mirrors of ordinary dimensions, as the actual

wave-length of this radiation is sufficiently small (1/2500 inch) to obviate trouble from diffraction.     The apparatus consists of a concave mirror mounted on a tripod. This mirror concentrates the object's infrared radiation on the blackened surface of a thermopile, consisting of minute wires of bismuth and silver soldered together. This blackened junction becomes slightly heated as the radiation is concentrated on it. The resulting electrical current, flowing through a galvanometer mounted on another tripod, indicates the presence of “something warm.”     Mr. Edison is not yet ready to divulge the details of his invention or reveal the exact principles involved in its operation. He has, however, said enough to lead to the belief that he plans to accomplish this modern miracle by means of a wonderful “spirit wireless”—an adaptation to communication between the world of the living and the world of the dead of the wireless telegraphy now in use on this earth.     Support of this view is given by Mr. Edison’s expectation that the first spirits to avail themselves of the means of communication he will offer them will be men and women who, during their earthly careers as telegraphers or scientists, became [xxx] in the use of delicate instruments and powerful electrical currents. It is also significant that he refers to the invention on which he is at work as an “apparatous”—the same term which would be used to describe a wireless telegraph outfit with its batteries, transmitters, receivers and lofty aerial towers.