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100. Thomson’s Experiments. Elect. Eng., N.Y., Mar. 11, Apr. 8 and Apr. 22, ’96. Elect. Rev., N.Y., Apr. 8, ’96, p. 183. Stereoscopic Sciagraphs. Elect. World, N.Y., Mar. 14, ’96.—Prof. Elihu Thomson, of the Thomson-Houston Electric Company, described experiments to determine the practicability of making stereoscopic pictures by X-rays. A solid object may be considered as composed of points which are at different distances from the eye. By monocular vision, the solidity of an object is not assured. However, by the use of both eyes, the objects appear less flat. The experimenter used, as the different objects, a mouse, also metal wires twisted together, and, again, a block of wood having projecting nails. In order to produce a stereoscopic picture with X-rays, he took a sciagraph in the ordinary way. He then caused the relative displacement of the discharge-tube and the object, and took another sciagraph. By mounting the two sciagraphs in a stereoscope, he found that the effect was as expected, and in the case especially of the skeleton of the mouse, it was very curious,—less like a shadow picture and more like the real object. The picture was more realistic, as in the well-known stereoscope for viewing photographs.

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:

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.

The author performed some experiments (Elect. Eng., N.Y., Apr. 15, ’96, p. 379) in relation to candle-power of X-rays by looking into a sciascope and moving it away until the luminosity just disappeared. He then detached the black paper cover from the phosphorescent screen and pointed the sciascope toward a candle flame and receded away until the fluorescence also disappeared. The distances, with different candles, would, of course, somewhat vary, but it would in the rough be a constant quantity, while different discharge tubes would cause the vanishing fluorescence at different distances. Now, assuming that the X-rays vary inversely as the square of the distance, as believed by RÖntgen, their power to fluoresce could, therefore, always be named as so much of a candle-power.

105. Simple Device for Comparing and Locating the Source and Direction of X-rays. Phosphorescence Not Essential.—In the ordinary sciascope, the fluorescent screen is located at one end, and the eyehole at the other. He modified this construction by employing a long straight tube, made of thick metal, so that X-rays could not enter through the wall. About at the centre of the tube was a diaphragm of a fluorescent material. Now, it is evident that if this is directed toward the phosphorescent spot and placed very close to the same, and the other end be looked into, the screen will become fluorescent, if X-rays are emitted from the area expected. Such a result occurred. With this instrument, he was able to show, in a similar way, that X-rays did not come from the anode, nor from the cathode directly. In one case, he provided a piece of platinum within the discharge tube, in such a position as to be struck by the cathode rays. § § 91 and 116. The instrument showed that X-rays radiated from the platinum, although the latter was not luminous nor phosphorescent,—illustrating again that phosphorescence is not a necessary accompaniment of X-rays, and assisting in upholding the principle that as the phosphorescence diminishes by increase of vacuum and increase of E. M. F., the X-rays increase. It should be noticed that Prof. Thomson emphasizes that the tube should be made of thick metal.

106. Rice’s Experiment. Apparatus for Obtaining X-Rays. § 109, 114, 131, 137. Tube Energized by a Wimshurst Machine. Elect. Eng., N.Y., Apr. 22, p. 410.—Roentgen had always employed the induction coil. As to those who first excited the discharge tube by the Holtz or Wimshurst machine or generators of like nature, it is not certain; but, according to public records, they were independently Prof. M. I. Pupin, of Columbia College, and Dr. William J. Morton, of New York. See Electricity, N.Y., Feb. 19, ’96. The accompanying cut marked “Rice’s Experiment, Fig. 1,” is a diagram representing the several elements of the apparatus, while “Rice’s Experiment, Fig. 2,” shows what kind of a sciagraph can be obtained by means of a Wimshurst machine. § 101, at centre. The details of the apparatus as employed by Mr. E. Wilbur Rice, Jr., Technical Director of the General Electric Co., were as follows: A Wimshurst machine, having a glass plate 16 inches diameter, coupled up with the usual small Leyden jars, spark under best conditions of atmosphere, etc., 4 inches. “The usual method of taking pictures with such a machine is to connect the interior coatings of the two jars, respectively, to the positive and negative conductors of the machine, the terminals of the discharge tube being connected between the external coatings of the Leyden jars. In this condition, the disruptive discharge of the Leyden jars passes through the tube and across the balls upon the terminals of the conductors of the machine, the length of spark being regulated by separating the balls in the usual way.” Later, he found that by omitting the Leyden jars, the generation of the X-rays was practically non-intermittent. He therefore connected the terminals of the discharge tube directly to those of the Wimshurst machine as indicated in “Rice’s Experiment, Fig. 1,” which also illustrates the details in the carrying out of the experiment for obtaining the picture, Fig. 2, of the purse containing the coins and a key. The principal feature was the introduction of a lead diaphragm containing a small central opening 7-8 inch diameter opposite the fluorescent spot. Sciagraphs taken thus required a little more time, about 60 minutes, while without the diaphragm, the time could be shortened to about 30 minutes, but the shadows were not so clear in the latter case. The figures are on p. 100.

107. Source of X-Rays Tested by Propagation Through a Small Hole.—This would illustrate not only that the fluorescent spot is the source of X-rays, but also that a very small portion comes from other parts that are probably bombarded by stray cathode rays (due to irregular surface of cathode § 57, or by reflected X-rays or cathode rays.

He tested the source of the X-rays by means of the following arrangement of the apparatus: It will be noticed that the lead diaphragm is quite close to the fluorescent spot. Upon holding the sciascope on the opposite side, and pointing it toward the spot, the luminous area of the fluorescent screen was about the same as that of the opening in the diaphragm, but the size grew rapidly upon receding from the diaphragm. If the rays had come from the cathode, however, the fluorescent spot on the screen would not have increased in size so rapidly during recession, and, therefore, the rays must have come from the spot on the glass struck by the cathode rays. § 113, 116, 117.

107a. Leeds’ and Stokes’ Experiment. Use of Stops in Sciagraphy. Western Electrician, Mar. 14, ’96.—In order to obtain clear definitions of the shadows, Messrs. M. E. Leeds and J. B. Stokes provided lead plates with holes, varying in size from 1/4 inch to an inch between the discharge tube on one side and the object and photographic plate on the other. In this manner they obtained excellent sciagraphs of animals having very fine skeletons. See the picture of the rattlesnake at § 135 and of a fish on page 63. See also the frog taken abroad page 90.

107b. Macfarlane, Morton, Klink, Webb and Clark’s Experiment. X-Rays From Two Phosphorescent Spots. Elect. World, Mar. 14, ’96.—By means of nails projecting vertically from a board (similar to the process carried out by Dr. William J. Morton, Elect. Eng., N.Y., Mar. 5, ’96), they proved, undoubtedly, that the source of the X-rays was at the surface of the glass directly opposite the cathode. By modification, which acted as further proof, a tube was provided with a cathode at the centre. There was a phosphorescent spot at each end. One board was placed laterally to the tube, and two shadows of each of certain nails were cast, which were caused as proved by measurement, by a double source of X-rays. This experiment illustrates the importance of preventing double shadows. The plate should be perpendicular to the line joining the two sources of the X-rays when there are two such sources. Even with the focus tube Dr. Philip M. Jones, of San Francisco, determined that there were two phosphorescent spots. These should be taken into account in all cases and attempts made to produce but one strong focus upon the platinum. Elect. World, N.Y., May 23, ’96.

108. Stine’s Experiments. Source of X-rays Determined by Sciagraphs of Short Tubes. Elect. World, N.Y., Apr. 11, ’96, pp. 392, 393.—Prof. Stine, of the Armour. Inst. of Tech., by means of the diagram shown in Fig. 1, p. 102, clearly proved that the X-rays have their source at the area struck by the cathode rays located directly opposite the disk marked “cathode.” If the reader will investigate the diagram and the sciagraphs, he will obtain a clearer knowledge of the evidence than by any verbal description, further than to explain how the elements are related to one another. In Fig. 1, therefore, will be noticed covered photographic plates, located as indicated with reference to the extreme left-hand end of the discharge tube, where the cathode rays strike. The surface of Plate 5 is parallel to that of the cathode, and the phosphorescent spot is in line between the two above named elements. The result is shown in Fig. 2, p. 102, the objects sciagraphed being several short sections of tubes with diameters varying from 1/2 to 3 inches.

A, in Figs. 3, 4, p. 104 and in Figs. 5, 6, p. 112, identifies the ends lettered A in Fig. 1. The sciagraph in Fig. 3 was obtained on the plate shown at the top in Fig. 1; that in Fig. 4, on Plate 2; that in Fig. 5, on Plate 3; and that in Fig. 6, on Plate 4. Not only were direct shadows visible, but also secondary shadows, indicating, therefore, that, although the source of practically all the rays was at the phosphorescent spot, yet a portion of the rays came slightly from other directions, either by reflection or by actual production of rays, upon other portions of the tube. Look now especially at Fig. 3, p. 104. If the rays came from the anode, then would this appearance necessarily be the same as that in Fig. 2. Similarly, the other sciagraphs may be considered to show that the rays do not come from the anode. In the case of the sciagraphs in Figs. 4, 5 and 6, only a single tube acted as the body for casting a shadow. Prof. Stine stated that the experiments were repeated over and over again, thereby establishing the phenomena as uniform.

109. Stine’s Electrical Apparatus Employed. § § 106, 112, 114, 131, 137.—Prof. Stine gave the following suggestive points:

“Among the first points investigated was the influence of the interrupter. The coil was provided, first with the familiar mercury make and break, and then an ordinary vibrator. The mercurial device gave very good results.

The small interrupter was found the more reliable, and seemed to shorten the needed time of exposure. A rotary contact-maker, giving two interruptions of the current per revolution, was also tested. This was driven by a motor with a condenser capacity of fourteen microfarads connected across the brushes. Owing to the large capacity of the condenser, a heavy current could be broken without marked sparking. The circuit breaker was tested at speeds ranging from 500 to 4,000 per minute, to note the influence on the time of exposure. The best results were obtained at the lower speed.... As no especial advantage could be noted when using the mercury breaker, it was abandoned for the vibrating interrupter.” This point is noted in detail, since so many experimenters seem to prefer such cumbersome devices, but they are, in reality, unnecessary.

110. Apparent Diffraction of X-Rays Really Due to Penumbral Shadows. Elec. Eng., Apr. 22, ’96, p. 408.—By referring to the diagram marked “Stine’s Experiment, Fig. A,” the arrangement of the elements may be seen, while the photographic print is shown in “Stine’s Experiment, Fig. B.” p. 106. Prof. Stine described the investigation as follows: Diffraction is naturally one of the first kinematical points to be investigated in the Roentgen experiments. It was noticed that when the opaque object was some distance from the plate, pronounced penumbral shadows resulted. These were of such width as to indicate diffraction. However, when such shadows are plotted back to the tube they are found to be purely penumbral, and not caused by diffraction. To completely demonstrate this point the experiment illustrated in Fig. A was undertaken. Here A₁ to A₄ are brass plates one inch wide and 1/8 inch thick, and of the length of the dry plate employed. They were first fastened together, so as to leave two parallel slots 1/8 of an inch wide. These plates are placed within 3/8 of an inch of the bulb, were one inch apart, and rested 1-1/8 inches above the dry plate. The resulting sciagraph is shown in Fig. B. In the diagram S₁ S₂, the edges of the penumbral shadow are very sharp and distinct. The direction of the rays is indicated, showing that there was absolutely no diffraction. This experiment has been modified in a variety of tests, with always the same result.”

110a. Jean Perrin’s Non-Diffraction. Comptes Rendus, Jan. 27, ’96. From trans. by Louis M. Pignolet.—The active part of a tube was placed before a very narrow slit; 5 cm. further, there was a slit 1 mm. wide; 10 cm. further, there was the photographic plate. An exposure of nine hours gave an image with sharply defined borders, upon which there was no diffraction fringe.

159a. Non-Refraction.—Refraction was attempted with prisms of paraffine and of wax, but no refraction was noticed.

111. Scribner and M’Berty’s Experiment. Source of X-Rays Determined by Interception of Assumed Rectilinear Rays From the Cathode. Elect. Eng., N.Y., Apr. 8, ’96, p. 358; Amer. Inst. Elec. Eng., Mar. 25, ’96. West. Branch.—Refer now solely to Fig. 1, S. and M.’s experiment. Notice the relative arrangement of the elements. First, the discharge tube with the cathode at the upper part and the phosphorescent spot opposite thereto; then below a thick lead plate with a single opening; then a second lead plate with two small openings placed laterally at such a distance that if there were rectilinear rays from the cathode they could not strike (by passing through the small hole), the covered photographic plate which was the next element in order. The description did not state that the photographic plate was covered, but the experimenters must have had the usual opaque cover upon it or else the luminous rays could have produced images. The developed plate showed two spots strongly acted upon and surrounded by portions which were less acted upon, the same as would be produced by light radiating from a surface as distinguished from a point. From the fact that they stated that the exposures were very long, it may be concluded also that the plates were covered by a material opaque to ordinary light. Measurement showed that the rays which produced the images came from the phosphorescent spot (§ 106, 109, 114, 131, 139) and not from the cathode directly by rectilinear propagation.

112. Source on inner Surface of the Discharge Tube Determined by Pin-Hole Images. Reference may now be made to S. and M.’s Experiment, Fig. 2.—The discharge tube has, as before, a cathode on one side, and the phosphorescent spot during operation on the opposite side. Lead plates were provided in positions indicated by the heavy black straight lines, there being a pin hole in each one. Behind these lead plates, measured from the discharge tube, were the covered photographic plates, as indicated. By measurement, it was afterwards determined that practically all the X-rays started from the phosphorescent spot. The electrode was put in an oblique position, as indicated, so that the same would not obstruct any X-rays trying to pass through the pin hole in the uppermost plate. The experiment served specifically to show that the X-rays started from the inner surface of the glass, because images produced on the upper and lower plates were equally strong. Perrin also found that the X-rays are developed at the interior sides of the tubes. (Comptes Rendus, Mar. 23, ’96. From trans. by L. M. P.) The rays, in producing each image, had to pass through an equal thickness of glass. If the rays had come from the outer surface, for example, two thicknesses would have been traversed by the rays striking the upper plate, and no thickness by those impinging upon the lower plate. That no rays came from any other portion or element of the discharge tube was evident, because a picture of the phosphorescent spot was the only one produced, and this picture was inverted, as usual, with pin hole cameras. (A pin-hole camera is the same as any other, with the lens replaced by a very small hole, which acts as a lens.)

In the way of further evidence, if not enough already, Meslans early determined that the phosphorescent spot on the glass is the source of X-rays (Comptes Rendus, Feb. 24, ’96. From Trans. by Mr. Louis M. Pignolet).

Jean Perrin’s Experiments. The Origin of X-rays. Comptes Rendus, Mar 23, ’96. From Trans. by Louis M. Pignolet.—He also confirmed that X-rays radiate from the phosphorescent spot.

112a. De Heen’s Experiment. The Anode Believed to be the Source of X-rays. Comptes Rendus, Feb. 17, ’96. From trans. by Louis M. Pignolet.—A lead screen, pierced by several holes, was placed between the discharge tube and the photographic plate. The shadows of the holes on the plate indicated that the rays emanate from the positive pole of the tube.

As both Thomson (E.) and Rowland, as well as De Heen, at first concluded likewise, is it not probable that the anode was struck by the cathode rays (see § § 113, 116)? For it was fully admitted that the anode, otherwise, does not emit X-rays.