From Sciagraph of Knee-joint, Straight, Side View, showing Patella, or Knee-cap.
By Prof. Goodspeed. Phot. Times, July, ’96.
The characteristics of wave motion are diffraction and interference phenomena. So far, no positive evidence of diffraction, [§ 110], nor interference, [§ 89], have been recognized, although experiments, have been tried that would have shown plainly, diffraction phenomena, had light been used in place of the Roentgen radiations. [§ 170]. We must, therefore, conclude, either that the Roentgen radiations in the experiments were too feeble to produce a record of the diffraction effects, or, that they are not due to wave motion at all, unless of a wave length very small even when compared with waves of light. The absence of refraction is also opposed to any wave theory of the Roentgen radiations, for it is difficult to believe that waves of any kind could travel with the same velocity through all media, which they must do if they suffer no deviation. [§ 86].
The next supposition naturally is, that the phenomena are due to streams of particles. It has been suggested that the rays may be streams of material particles, but this theory cannot be maintained in view of the fact that the rays proceed, without hindrance, through the highest vacuum. [§ § 72b] and [133], near end. Neither is it consistent with the high velocity of propagation. Molecules of gas could not be propelled through air with any such velocity or to any such distance as X-rays are propagated. Tesla has claimed [§ 139], that the residual gases are driven out through the glass of the vacuum bulb by the high potential that he employs. This has not been confirmed by other experimenters. It has been observed that the vacuum may be greatly improved by working the bulb, [§ 121], that is, sending the discharge through it, but experimenters generally have found that heating the bulb impairs the vacuum and restores the original condition. The gases, were, therefore, occluded during the electrical discharge, to be again set free by heating the bulb. [§ 139b]. The rays may be ether streams, perhaps in the form of moving vortices, but of such streams we have no independent knowledge, and can only determine by mathematical analysis, what their characteristics should be. They would not suffer refraction, and would not produce interference nor diffraction phenomena. Whether they would do what the X-rays do, go through the flesh and not through bone, through wood and not through metal, excite fluorescence, or affect the photographic plate, cannot be said. There is evidence that there are at least two kinds of X-rays, [§ 152], differing in penetrating power, though perhaps not differing in other respects.
From Sciagraph of Normal Knee-joint, Flexed.
Phot. Times, July, 96.
Copyright, 1896, by William Beverley Harison, Publisher of “X-ray” Pictures, New York.
X-rays have their origin only in electrical discharges in high vacua. They are absent from sun-light and from light of the electric arc, and other sources of artificial illumination, [§ 136]. Proceeding from the bombarded spot, they are not deflected by a magnet, except in an evacuated observing tube, as proved by Lenard, [§ 72a], and show no evidence of carrying an electric charge like cathode rays, [§ 61b], p. [47]. On the contrary, they will discharge either a negatively or positively charged body in their path. The evidence seems conclusive (Chap. [VIII].) that the ultra-violet rays from an illuminating source also discharge charged conductors. In this respect, therefore, there is a similarity between the X-rays and ultra-violet light.
The action of the waves of light upon a cell formed of selenium lowers the resistance of the latter and herein is circumstantial evidence at least, concerning the similarity of the properties of X-rays and light, because the former are also found to increase the conducting power of selenium. [§ 171].
The experiments of Roentgen, [§ 90], seem to show that the discharging effect of X-rays is due to the air through which the rays have passed.
It is certain that the discharge of electrified bodies by light occurs more generally for negatively than for positively charged bodies, [§ § 99B], [99I], and [99S], that it depends upon the nature, [§ 97b], and density, [§ 97a], of the gas surrounding the body, and also upon the material of the charged body itself. [§ 98]. The discharge would, therefore, seem to be connected with a chemical action, [§ 153], near end, which is promoted by the rays. This seems all the more probable, since it was found, [§ 98], that the more electro-positive the metal, the longer the wave length that would influence the discharge. In this connection, it is well to note that Tesla found, [§ 146a], that in their power of reflecting (or diffusing X-rays), the different metals stand in the same order as in the electric contact series in air, the most electro-positive being the best reflectors. It would be interesting to know whether connecting the reflecting plate to earth, would, in any way, vary its reflecting power.
The X-rays seem to discharge some bodies, when positively charged, and other bodies when negatively charged. They will also give to some bodies a positive, and to others a negative charge ([§ 90c]). Is the order here also that of the electrical contact series in air? Are not all the phenomena of electrical charge and discharge, of reflection or diffusion, and of X-rays, connected with chemical action, as the apparent difference of potential, due to contact, undoubtedly is? [§ 153].