Now let us consider briefly the Roentgen ray phenomena that bear upon the question of the nature of the propagation.
From Sciagraph of Normal Elbow-joint; Straight, in Position of Supination.
By A. W. Goodspeed. Phot. Times, July, ’96.
Copyright, 1896, by William Beverley Harrison, Publisher of “X-ray” Pictures, New York.
It seems to be settled beyond question that the origin of the Roentgen rays is the fluorescent spot in the discharge tube. [§ § 107], [108], [111]. The evidence seems overwhelming that within the tube, the phenomena are the result of streams of electrified particles of the residual matter, shot off from the cathode in straight lines, perpendicular to its surface. [§ 57]. This was Crookes’ original theory, [§ 53], near centre, and it seems to have stood well the test of scientific criticism. These flying particles falling upon anything in their path, give rise to X-rays. It is preferable, but not essential, that the bombarded surface should be connected electrically with the anode. [§ § 113], and [116]. The best results are obtained by using a concave cathode, and placing at its centre the surface which is to receive the bombardment, thereby concentrating the effect upon a small area.
Nearly all experimenters agree in locating the origin of the X-rays at this bombarded spot. The energy here undergoes a transformation, and the X-rays represent one of the forms of energy developed.
What are the characteristics of this particular form of radiant energy?
It causes certain salts to fluoresce, [§ § 66], [84], and [132], and it affects the photographic plate. [§ § 70] and [84]. In these respects, it is like the short wave length radiations from a luminous source. It is, however, totally unlike these in its power of penetrating numerous substances entirely opaque to light, such as wood, paper, hard rubber, flesh, etc. In passing through hard rubber and some other opaque insulators, X-rays are like the long wave length radiations from heated bodies, but X-rays penetrate many substances that are opaque to these long wave length radiations, and they are especially distinguished from all forms of radiant energy previously recognized, in their relative penetrating power for flesh and bones which makes it possible to obtain the remarkable shadow pictures which have become within three or four months, so familiar to all the world.
But these phenomena, although they serve to distinguish the X-rays from all other forms of radiant energy, do not furnish any clew to the nature of the X-rays themselves.
In attempting to formulate a theory of X-rays, the idea that first naturally presents itself is that they are due to some form of wave motion.
