The utility of the telephone has been greatly increased by the inventions of Hughes and Edison of the _microphone_. This consists, in one form, of pieces of carbon in loose contact placed in the circuit of a telephone. The very slightest vibrations communicated to the wood are heard distinctly in the telephone. By these inventions and certain improvements not only every sound and note of an opera or concert has been carried to distant places, but the slightest whispers, the minute movements of a watch, even the tread of a fly, and the pressure of a finger, have been rendered audible. By the aid of the electric current certain rays of light directed upon the mineral selenium, and some other substances, have been discovered to emit musical sounds. So wonderful and mysterious appear these communications along the electric wire that each and every force in the universe seems to have a voice awaiting utterance to man. The hope is indulged that by some such means we may indeed yet receive the “touch of a vanished hand and the sound of a voice that is still.” In 1879 that eminent English scientist, Prof. Wm. Crookes, published his extensive researches in electrical discharges as manifested in glass tubes from which the air had been exhausted. These same tubes have already been referred to as Geissler tubes, from the name of a young artist of Bonn who invented them. In these tubes are inclosed various gases through which the sparks from an induction coil can be passed by means of platinum electrodes fused into the glass, and on the passage of the current a soft and delicately-tinted light is produced which streams through the tube from pole to pole. In 1895, Wm. Konrad Roentgen, professor of Physics in the Royal University of Würzburg, while experimenting with these Crookes and Geissler tubes, discovered with one of them, which he had covered with a sort of black cardboard, that the rays emanating from the same and impinging on certain objects would render them self-luminous, or fluorescent; and on further investigation that such rays, unlike the rays of sunlight, were not deflected, refracted or condensed; but that they proceeded in straight lines from the point at which they were produced, and penetrated various articles, such as flesh, blood, and muscle, and thicknesses of paper, cloth and leather, and other substances which are opaque to ordinary light; and that thus while penetrating such objects and rendering them luminous, if a portion of the same were of a character too dense to admit of the penetration, the dark shadow of such obstacle would appear in the otherwise luminous mass. Unable to explain the nature or cause of this wonderful revelation, Roentgen gave to the light an algebraic name for the unknown--the X rays.