In this connection, it should be remembered that there are not only cathode rays, X-rays, etc., but the electric force that Lenard spoke of in the neighborhood of the discharge tube, and in testing the effects upon the eyes, of course, the precaution should be taken to determine whether cathode rays, X-rays or the electric sparks are answerable for the peculiar effects. Roentgen reasoned, [§ 84], that the eyes were not sensitive, but the rays, in his case, were not strong enough to travel 40 to 60 feet, as in Tesla’s experiments, but only 2 m. (about 7 ft.).
142. Sciagraphs of Hair, Fur, Heart, Etc., by X-rays.—Tesla was probably the first to be at all successful in the representation in sciagraphs of such objects as hair and cloth and similar easily permeable objects. In the case of a rabbit, not only was the skeleton visible, but also the fur. Sciagraphs of birds exhibited the feathers fairly distinctly. The picture of a foot in a shoe not only represented the bones of the foot, and nails of the shoe, but every fold of the leather, trowsers, stockings, etc. His opinion as to the useful application of the rays was that any metal object, or bony or chalky deposit could be “infallibly detected in any part of the body.” In obtaining a sciagraph of a skull, vertebral column, and arm, even the shadows of the hair were clearly apparent. It was during such an experiment that the anæsthetic qualities were noticed. The author saw several of the above named sciagraphs. Furthermore, on the screen he believed he detected the pulsations of the heart. Elect. Rev., N.Y., May, 20, ’96.
Although we do not doubt this report concerning what Mr. Tesla saw, yet some scientific men are exceedingly dubious concerning the results obtained by other scientists, unless the same are confirmed by additional witnesses. It will certainly be of interest to such skeptics to have corroboratory evidence. In company with Prof. Anthony, Mr. Wm. J. Hammer and Mr. Price, editor of the Elect. Rev., N.Y., the author visited a laboratory at 31 West 55th street, New York City, for the purpose of beholding the pulsations of the human heart by means of an experiment performed by Mr. H. D. Hawkes, of Tarrytown, N.Y. There was nothing new about his apparatus, the admirable results being due merely to accurately proportioned electrical and mechanical details and skillful manipulation. The Tesla system was not used, but merely a large induction coil and rotary interrupter, and a direct current from the incandescent lamp circuit of 110 volts, all substantially as Roentgen himself employed. The sciascope was provided with the Edison calcic tungstate screen. In order to overcome the sparking between the terminals on the outside of the tube after a few minutes of use, he heated the cathode end by means of a Bunsen burner flame. [§ 139], near beginning. The utility consisted in the evaporation of condensed moisture upon the cool end of the discharge tube. The temporary heating always prevented, for several minutes, any sparking on the outside. After some preliminary experiments, each person, in turn, pressed the sciascope upon the breast of another, at the location of the heart, while the discharge tube was directly at the back of a young man. The ribs and spinal column were visible, and, projecting from the spine, appeared a semi-circular area, which expanded and contracted. Any one viewing such an operation, and knowing that he is looking at the movements of the heart, cannot but be impressed with weird wonder, and cannot but credit great honor, not only to Roentgen and Lenard, but to all those early workers who have gradually but surely, successfully made discovery after discovery in the department of the science of discharges, finally culminating in the most wonderful discovery of all.
The author remembers seeing in some medical paper that William J. Morton, M.D., of New York, had also witnessed the beating of the heart with the sciascope at an early date. Similar reports are occurring weekly.
§ 142a. Mr. Norton, of Boston (Elect. World., N.Y., May 23, ’96) also stated that the heart could be seen in faint outline, and also its pulsations. The lungs were very transparent. The liver being quite opaque, its rise and fall with the diaphragm was plainly followed. Others have suggested drinking an opaque (to X-rays) liquid, like salt water, and tracing its path.
143. Propagation of X-rays through Air to Distances of 60 Ft.—In Roentgen’s first experiments, the maximum distances at which the fluorescent screen was excited was about 7 ft. Tesla obtained similar action at a distance of over 40 ft. Photographic plates were found clouded if left at a distance of 60 ft. for any length of time. This trouble occurred when some plates were in the floor above and 60 ft. distant from the discharge tube. He attributed the wonderful increase largely to the employment of a single electrode discharge tube, because the same permitted the highest obtainable E. M. F. that could be desired.
Sciagraph of Foot in Lace Shoe. [§ 204].
By Prof. Miller.
144. X-rays with Poor Vacuum and High Potential.—In the course of Tesla’s experiments, he observed that the Crookes’ phenomena and X-rays could be produced without the high degree of vacuum usually considered necessary, [§ 118]. but by way of compensation, the E. M. F. must be exceedingly high, and, of course, the tube and electrical apparatus substantially of those dimensions involved in Tesla’s work. One must be careful not to over-heat the discharge tube, which is likely to occur by increase of potential. He gave definite instructions for preventing the destruction of the tube by heating, by stating that it is only necessary to reduce the number of impulses, or to lengthen their duration, while at the same time raising their potential. For this purpose, it is best to have a rotary circuit interrupter in the primary instead of a vibrating make and break, for then it becomes convenient to vary the speed of the interrupter, which may be, evidently, so constructed that the duration of the impulses may also be varied, for example, by different sets of contact points arranged on the rotary interrupter, and made of different widths.
145. Detail Construction and Use of Single Electrode Discharge Tubes for X-rays. He pointed out that with two electrodes in a bulb as previously employed by nearly all experimenters, or an internal one in combination with an adjacent external one the E. M. F. applicable was necessarily greatly limited for the reason that the presence of both, or the nearness of any conducting object “had the effect of producing the practicable potential on the cathode.” Consequently he was driven, as he said, to a discharge tube having a single internal electrode, the other one being as far away as required. [§ 9]. In view of his ingenious arrangements of the disruptive coil, and circuits, condensers and static screens for the bulb, he found it immaterial to pay attention to some other details followed by experimenters. For example, it made comparatively little difference in his results whether the electrode was a flat disk or had a concave surface.