Multiple Sciagraphs. Fig. 2, [§ 101], p. [95].
101. Thomson’s Experiment. Manifolding by X-rays.—If one desires to take a print of a negative, for example by means of sun-light, it is evident that, on account of the opacity of the photographic paper, only one sheet would be placed under the negative for receiving a print. However, the X-rays are so penetrating in their power that it is possible for them to produce sciagraphs through several sheets, and thereby to result in the production of several pictures of the same object with one exposure. Without an experiment to prove this, one might argue that the chemical action of one sheet would absorb all the energy. The experiment of Prof. Thomson shows that this is not so. The elements were arranged as follows: First a discharge tube; then an object, namely, a key escutcheon of iron; then yellow paper; then paste board; then black paper; then two layers of albumen or sensitized paper; then two célérité printing papers; then two platinum printing papers; then one célérité; then six layers of sensitive bromide paper; then four layers of heavy sensitive bromide paper (heavier); then three layers of black paper, and finally, at the maximum distance from the discharge-tube, a sensitive glass plate of dry gelatine, with its face up, thereby making twenty-five layers in the aggregate. It is interesting to notice that an induction coil was not employed, but a small Wimshurst machine, having connected to each pole a small Leyden jar. [§ 106]. 1,200 discharges occurred during exposure. The results were as follows: No sciagraphs developed upon the albumen, célérité nor platinum, which, it should be noticed, were merely printing papers. [§ 128]. The impressions on the ten bromide papers were weak. See Multiple Sciagraphs, Fig. [2], p. [94]. He attributed the reason of this to the thinness of the film. Although the glass plate was furthest away from the discharge tube, yet the impression was greater than on any of the papers, the result being shown in Multiple Sciagraphs, Fig. [1], p. [94]. He suggested that the plates for use with X-rays should have unusually thick films. Incidentally he found that the intensifying process could be employed with profit to bring out the small details distinctly. Dr. Lodge also recommended thick films. See The Elect., Lon., Apr. 24, ’96., p. 865.
101a. Lumière’s Experiment. Enormous Transparency of Sensitive Photographic Paper. Comptes Rendus, Feb. 17, ’96. Translated by Mr. Louis M. Pignolet.—With a ten-minutes exposure, objects were sciagraphed through 250 super-imposed sheets of gelatino-bromide of silver paper, to observe the absorption of the X-rays by the sensitive films. The one hundred and fiftieth sheet was found to have an impression.
102. Proposed Double Cathode Tube. See also Elect. Rev., N.Y., Apr. 15, p. 191.—The nature of this will be apparent immediately from the cut which is herewith presented and entitled “Standard X-Ray Tube.” With unidirectional currents the concave electrodes in the opposite ends may each be a permanent cathode, while the upper terminal connected to the angular sheet of platinum may be the anode. Cathode rays, therefore, will be sent out from each concave disk, and striking upon the platinum will be converted into X-rays, assuming that the platinum is the surface upon which the transformation from one kind of ray to another takes place. [§ 63], at end. This is called a standard tube, because it may be employed with efficiency with any kind of generator. [§ 8a], [26a], [115], [116] and [145]. It is interesting to notice a confirmation of the efficiency of such a tube, for Mr. Swinton, in a communication to the Wurz Phys. Med. So. (see The Elect., Lon., and Elect. Eng., N.Y., June 3,) showed and described a picture of an exactly similar tube. By an experiment, the tube operated as expected. First proposed by Prof. Elihu Thomson, who is an author also of the following experiment:
Standard X-Ray Tube.
103. X-Rays. Opalescence and Diffusion. Elect. World, Apr. 25, ’96.—He alluded to opal glass and milk to illustrate that light is reflected not only at the surface of a body, but from points, or molecules, or particles, located underneath the surface. By some experiments with X-rays, he found that they had a similar property only not to such a large per cent., but on the other hand by the way of contrast, there are many more substances opalescent to X-rays than there are to light, for the reason that the former will penetrate more substances and to greater distances. He made many observations with a modified sciascope, [§ 105], by pointing it away from the discharge tube and towards different substances struck by X-rays. To all appearances, such substances became the sources of the X-rays. He alluded to Mr. Tesla’s experiments on reflection, [§ 146], but noticed that there was a slight difference between reflection and diffusion and he was satisfied that reflection took place from the interior of the substances as well as from the surface. Metal plates, he said, gave apparently little diffusive effect, appearing to reflect feebly at angles equal to the incident angles. He alluded to Edison’s experiment also, [§ 133], with a large thick plate cutting off the X-rays and attributed the luminosity of his modified sciascope to rays both reflected and diffused from surrounding objects, which generally as a matter of course, are more of non-metallic objects than metallic, such as floor, ceiling, walls, tables, chairs and so on. Evidently, the interior of one’s hand causes diffusion; very little, however, for a sciagraph by means of a focus tube gives wonderfully clear outlines, and yet the rays do not come from a mathematical point. [§ 88]. Prof. Thomson acknowledged that independently of himself, Dr. M. I. Pupin, of Columbia College, had reported in Science, Apr. 10, ’96, see also Electricity, Apr. 15, ’96, p. 208, upon investigations on the same general subject, namely diffusion, and also referred to experiments of Lenard, [§ 69], and Roentgen on diffusion. Agrees also with experiments of A. Imbert and H. Bertin-Sans in Comptes Rendus, Mar. 2, ’96. He suggested that this property of diffusion acted as an explanation why sciagraphs can never have absolutely clearly cut shadows of the bones or other objects imbedded in a considerable depth of flesh.
103a. A. Imbert and H. Bertin-Sans’ Diffusion and Reflection in Relation to Polish. X-Rays. Comptes Rendus, Mar. 2, ’96. Translated by Louis M. Pignolet.—They concluded, under the conditions of their experiments, that if X-rays were capable of reflection it was only in a very small proportion; on the other hand, the rays can be diffused en assez grande quantité, the intensity of the diffusion appearing to depend much more upon the nature of the diffusing body than upon its degree of polish. From this they attributed to the rays a very small wave length, such that it would be impossible to get in the degree of polish necessary to obtain their regular deflection. Perrin attempted unsuccessfully to reflect the rays from a polished steel mirror and a plate of “flint,” but with exposures of one hour and seven hours respectively, nothing was obtained. From trans. by L. M. Pignolet, Comptes Rendus, Jan., 96. By exposing a metal plate to the rays and suitably inclining it in front of the opening, Lafay also proved reflection, for it was possible to discharge the electrified screen; hence, as he called it, diffused reflection. Comptes Rendus, Apr. 27, ’96; from trans. by L. M. Pignolet.
104. Fluorometer.—He constructed an instrument for comparing the merits of different discharge tubes, and for indicating the comparative luminosity of different screens subjected to the action of the same discharge tube. The instrument served also to act as an indicator of the diffusing power of different materials. “By placing two exactly similar fluorescent screens at opposite ends of a dark tube, and employing a Bunsen photometer screen, movable as usual between the screens, a comparison of the diffusing power of different materials might be made by subjecting the pieces placed near the ends of the photometer tube outside, to equal radiation from the Crookes’ tube.” From Prof. Thomson’s description.