90d. Benoist & Hermuzescu’s Experiment. Negative Charges Dissipated Faster Than Positive By X-Rays. Rate Depends Upon Absorption. Law Formulated. Comptes Rendus, Feb. 3, Mar. 17 and April 27, ’96. They observed that the rays dissipated entirely the charge of electrified bodies in their path, and that negative charges were dissipated more rapidly than positive. [§ 99Q]. They also noticed the discharge augments with the opaqueness of the body and that the effect is more considerable with two thin superposed sheets than with one. In experimenting upon the influence of the discharge of the gaseous dielectric in which the bodies were located, they formulated the following law. The rapidity of the dissipation of the electric charge of an electrified body under the same condition varies as the square root of the density of the gas surrounding the body. The dissipation of the electric charge depends upon the nature of the electrified body, due to a sort of absorbing power ([§ 99M]) connected with the opaqueness of the body and upon the nature of the surrounding gas, due to the density of the gas or when passing from one gas to another. (From trans. by Louis M. Pignolet.)
91. Before Roentgen published in his second paper of Mar. 9, ’96, an account of his focus tube, the Kings College published a description of an exactly similar one, represented in the cut. See Elec. Rev., Lon., Mar. 13. ’96, p. 340. The cathode is concave and the anode is formed of platinum and is plane and at such an angle that the X-rays generated, [§ 63b]., on diffusion of internal cathode rays, will be thrown out through the thin walls of the bulb. [§ 55] and [57]. As the rays emanate from a point, the shadows are much clearer, especially in conjunction with powerful rays permitting several feet between the object and the tube. Mr. Shallenberger was among the first, and was the first as far as the author knows (Elect. World, Mar. 7, ’96, see cut reproduced) to originate the use of an X-ray focus tube.
Typical Focus Tube.
91a. Apparatus Employed.—Prof. Roentgen paid tribute to Tesla, by alluding to the advantages resulting from the use of the Tesla condenser and transformer. In the first place, he noticed that the discharge apparatus became less hot, and that there was less probability of its being pierced. Again the vacuum lasted longer, at least in the case of his particular apparatus. Above all, stronger X-rays were produced. Again careful adjustment of the vacuum was not as necessary as with the Ruhmkorff coil.
92. X-Rays and Longitudinal Vibrations.—Prof. Roentgen did not consider X-rays and ultra-violet rays to be of the same nature, although they produced many common effects. The X-rays, as he found, by the above related experiments, behaved quite differently from the ultra-violet rays, which are highly refrangible, practically all subject to reflection, capable of being polarized, and absorbed according to the density of the absorbents. For valid reasons, the X-rays cannot be infra-red rays. While he does not affirm any theory, yet he suggests the theory of longitudinal waves for explaining the properties of X-rays. (This was not suggested again in his second announcement.) He stated that the hypothesis needs a more solid foundation before acceptance. The reason why Roentgen termed the energy X-rays is simply because X in algebra represents an unknown quantity.
Shallenberger Apparatus and Focus Tube. [§ 91].
93. At the Johns Hopkins University, U. S., in 1884, Sir William Thomson, (Kelvin) delivered a lecture in which he argued that the production of longitudinal vibrations, by electrical means, is reasonable and possible of occurrence. J. T. Bottomly, in Nature, Lon. Feb., (see also Elect. Eng., N.Y., Feb. 19, ’96, p. 187) called attention to this lecture as being of interest in view of Roentgen’s suggestion about longitudinal vibrations. Lord Kelvin called attention to what had been developed in connection with the electro-magnetic theory of light and referred to his own work in 1854, in connection with the propagation of electric impulses along an insulated wire surrounded by gutta percha, but he said that at that time no one knew the relation between electro-static and electro-magnetic units. The part of the lecture referring particularly to the possibility of longitudinal waves in luminiferous ether by electrical means reads as follows. “Suppose that we have at any place in air, or in luminiferous ether (I cannot now distinguish between the two ideas) a body that, through some action we need not describe, but which is conceivable, is alternately, positively and negatively electrified; may it not be that this will give rise to condensational waves? Suppose, for example, that we have two spherical conductors united by a fine wire, and that an alternating E. M. F. is produced in that fine wire, for instance, by an alternate current dynamo-electric machine, and suppose that sort of thing goes on away from all other disturbance—at a great distance up in the air, for example. The result of the action of the dynamo-electric machine will be that one conductor will be alternately, positively and negatively electrified, and the other conductor negatively and positively electrified. It is perfectly certain, if we turn the machine slowly, that in the air in the neighborhood of the conductors, we shall have alternately, positively and negatively directed electric force with reversals of, for example, two or three hundred per second of time, with a gradual transition from negative, through zero to positive, and so on; and the same thing all through space; and we can tell exactly what the potential and what the electric force are at each instant at any point. Now, does any one believe that, if that revolution were made fast enough, the electro-static law of force, pure and simple, would apply to the air at different distances from each globe? Every one believes that if the process can be conducted fast enough, several million times, or millions of millions times per second, we should have large deviations from the electro-static law in the distribution of electric force through the air in the neighborhood. It seems absolutely certain that such an action as that going on would give rise to electrical waves. Now, it does seem to me probable that these electrical waves are condensational waves in luminiferous ether; and probably it would be that the propagation of these waves would be enormously faster than the propagation of ordinary light waves.” Notice that the above was written twelve years prior to Roentgen’s discovery.
94. Prof. Schuster, in Nature, Lon., Jan. ’96, stated that the great argument against the supposition of waves of very small length lies in the absence of refraction, but questioned whether this objection is conclusive. He further stated: “The properties of the ether may remain unaltered within the greater part of the sphere of action of a molecule. The number of molecules lying within a wave length of ordinary light is not greater than the number of motes which lie within a sound wave, but, as far as I know, the velocity of sound is not materially affected by the presence of dust in the air. Hence there seems nothing impossible in the supposition that light waves, smaller than those we know of, may traverse solids with the same velocity as a vacuum. We know that absorption bands greatly affect the refractive index in neighboring regions; and as probably the whole question of refraction resolves itself into one of resonance effects, the rate of propagation of waves of very small lengths does not seem to me to be prejudged by our present knowledge. If Roentgen rays contain waves of very small length, the vibrations in the molecule which respond to them, would seem to be of a different order of magnitude from those so far known. Possibly, we have here the vibration of the electron with the molecule, instead of the molecule carrying with it that of the electron.”