CHAPTER XI
137. Tesla’s Experiments. Elec. Rev., N.Y., March 11, ’96, page 131, March 18, page 147, April 1, page 171, and April 8, page 183. Kind of Electrical Apparatus for Operating Discharge Tubes for Powerful X-rays. [§ 106], [109], [114], [131]. The experiments performed by Nikola Tesla were particularly noteworthy for the magnitude and intensity of the rays generated by his apparatus, under his skilful manipulation of the adjustments and circuits particularly as to resonance. The remarkable results that he obtained are not surprising when we learn that he employed his well-known system for producing exceedingly enormous potential and unusually high frequency. [§ 51]. The primary electrical generator as he indicated and as apparent from his system referred to in the above section, could be either a direct or alternating current generator, or other form. If the first is employed, of course an interrupter is necessary in order that there may be a current induced in the secondary.
Sciagraph of Rat, Taken by Oliver B. Shallenberger with Focus tube
(CUT AT p. [81]) and Tesla System. [§ 137], pp. [136] and [138].
Mr. Oliver B. Shallenberger, (Mem. Amer. Inst. Elec. Eng.) whose laboratory is in Rochester, Pa., gave some important general instructions concerning the Tesla system [§ 51], that he employed in the production of remarkably clear sciagraphs, in conjunction with the focus tube, [§ 91], representing the hand at page 68, and showing a rat shown at this [§ 137]. (Elec. World, N.Y., March 17, ’96.) Even the ligaments were clearly shown in the sciagraph of the rat, and some of them are dimly reproduced by the half tone process. As to the apparatus and operation, which are especially important, it may be stated that the current was taken from an alternator, of a frequency of 133 periods per second, and passed through a primary coil of a transformer for increasing the E. M. F. from 100 volts to from 16 to 25 thousand. The secondary current was then passed through Leyden jars and a double cascade of slightly separated brass cylinders, whereby it was changed into an oscillatory current of an extremely high frequency, which was then conducted through the primary of a second induction coil having very few turns of wire, and no iron core and having a ratio of 7 to 1. By this means the E. M. F. was raised to somewhere between 160,000 volts to 250,000, and was used to energize the discharge tube for the generation of X-rays. Caution should be taken, because the current coming from the first transformer, being of large quantity and very high E. M. F. is exceedingly dangerous, but the current of the second secondary has been passed through one’s body without danger, as reported by Mr. Tesla several years ago, and confirmed by Mr. Shallenberger.
138. Phosphorescent Spot Maintained Cool.—In testing the power of the X-rays in connection with the appearance of the phosphorescent spot, Tesla noticed that they were most powerful when the cathode rays caused the glass to appear as if it were in a fluid state. [§ 61]. To prevent actual puncture, he maintained the spot cool by means of jets of cold air. It became possible thereby to use bulbs of thin glass at the location of the generation of the X-rays. [§ 119]. He concluded from certain results that not only was glass a better material for discharge tubes than aluminum, but because, by other tests, he found that thin aluminum cast more shadow with X-rays than thicker glass. There are, of course, many other reasons, based on mechanical construction, why glass is preferable, and also why a tube with an aluminum window is not to be desired. Principally, the latter will soon leak.
139. Expulsion of Material Particles through the Walls of a Discharge Tube.—At quite a low vacuum, and after sealing off the lamp, he attached its terminal to that of the disruptive coil. After a while, the vacuum became enormously higher, as indicated by the following steps: First, a turbid and whitish light existed throughout the bulb. This was the first principal characteristic. Next, the color changed to red, and the electrode became very hot, in that case where powerful apparatus was employed. The precaution should be taken to regulate the E. M. F., to prevent destruction of the electrode. Gradually, the reddish light subsided, and white cathode rays, which had begun, grew dimmer and dimmer until invisible. At the same time, the phosphorescent spot became brighter and brighter and hotter and hotter, while the electrode cooled, until the glass adjacent thereto was uncomfortably cold to the touch. At this stage, the required degree of exhaustion was reached, and yet without any kind of a pump. He was enabled to hasten the process by alternate heating and cooling, and by the use of a small electrode. This whole phenomenon was exhibited with external electrodes as well. He acknowledged that instead of the disruptive coil, a static machine could be used, or, in fact, any generator or combination of devices adapted to produce a very high E. M. F.
The reduction of temperature of the electrode he attributed to its volatilization. Without actually testing the rays with a fluorescent screen or photographic plate, he could always know their presence by the relative temperatures of the phosphorescent spot and the electrode, for when the latter was at a low temperature and the former at a high temperature, X-rays were sure to be strong.
From the fact that the vacuum became higher and higher by the means stated, he was very much inclined to believe that there was an expulsion of material particles through the walls of the bulb. When these particles which were passing with very great velocities struck the sensitive photographic plate they should produce chemical action. He referred to the great velocity of projected particles within a discharge tube, pages [46] and [47], and to Lord Kelvin’s estimate upon the same, and reasoned that with very high potentials, the speed might be 100 km per second. The phenomenon indicated, he said, that the particles were projected through the wall of the tube and he entered into an elaborate discussion on this point. He referred to his own experiment of causing the rays from an electrode in the open air to pass directly through a thick glass plate. [§ 13]. He performed an experiment also of producing a blackening upon a photographic plate apparently by the projected particles, an electrical screen being employed to prevent the formation of sparks. [§ 35]. which as well known will cause chemical action upon the plate. No stronger proof as to the expulsion of material particles could be desired than an operation in which the eyes can see for themselves that such an action must have taken place. Usually he was troubled by the streamers (cathode rays) from the electrode suddenly breaking the glass of the discharge tube. This occurred when the spot struck was at or near the point where the same was sealed from the pump. He arranged a tube in which the streamers did not strike the sealing point, but rather the side of the tube. It was extraordinary that a visible but fine hole was made through the wall of the tube, and especially that no air rushed into the vacuum. On the other hand, the pressure of the air was overcome by something rushing out of the tube through the hole. The glass around the hole was not very hot, although if care were not taken, it would become much hotter, and soften and bulge out, also indicating a pressure within, [§ 27]. greater than the atmospheric pressure. He maintained the punctured tube in this condition for some time and the rarefaction continued to increase. As to the appearances, the streamers were not only visible within the tube, but could be seen passing through the hole, but as the vacuum became higher and higher, the streamers became less and less bright. At a little higher degree of vacuum, the streamers were still visible at the heated spot, but finally disappeared.
This electrical process of evacuating varies in its rapidity according to the thinness of the glass. Here again he noted the application of his theory in that an easier passage was afforded for the ions. [§ 47]. A few minutes of operation produced through thin glass, a vacuum from very low to very high, whereas, to obtain the same vacuum through much thicker glass over 1/2 hour was necessary. Again with a thick electrode the time required was much greater. The small hole was not always visible and it was thought that the material went through the pores. The result obtained by the following experiment tends to uphold Mr. Tesla’s emission theory.
139a. Lafay’s Experiment. Giving to X-rays the Property of Being Deflected by a Magnet by Passing Them Through a Charged Silver Leaf. Comptes Rendus, March 23, ’96 and April 7, 13, 27, and L’Ind. Elec., April and May ’96. From trans. by Louis M. Pignolet. He placed at about .5 cm. below a discharge tube, a lead screen pierced by a slit 2 mm. wide; and 0.04 m. lower, a second lead screen having a slit 5 mm. wide completely covered by an extremely thin leaf of silver. Opposite the silver leaf and exactly in the axis of the slit, was fixed a platinum wire 1.5 mm. diameter. Thus, the rays which passed successively through the two slits projected a shadow of the wire on a photographic plate below.
When the silver leaf was connected to the negative pole of the induction coil that excited the tube, the rays, which had become electrified ([§ 61b], p. [47]) bypassing through the leaf, were deflected by a magnetic field of about 400 L. G. S. units, whose lines of force were parallel to the slit. The direction of the deflection was determined by the same law as that of the deflection by a magnetic field of the cathode rays in the interior of a discharge tube. [§ 59]. When the silver leaf was not connected to the coil, no deflection was produced. [§ 79].
To double the apparent deflection, one part of the slit was covered by a lead plate during the first half of the experiment. The lead plate was removed and placed over the other part of the slit, and the direction of the magnetic field reversed during the last half of the experiment. Thus the distance on the sciagraph between the two parts of the wire, was double the deflection produced by the magnetic field.
The deflection was in the same direction when the silver leaf was connected to the negative pole of a static electric machine, but was in the opposite direction when the leaf was connected to the positive pole of the machine. The test was criticised in the scientific press, and, therefore, in order to be certain that the deflections observed were not due to the combined effects of the electro-magnet which produced the magnetic field and the electric field of the charged silver leaf, the experiments were modified. To remove this uncertainty, the electrified rays were caused to enter a grounded Faraday cylinder (see figure at E. F. G. H., p. [47]), through a small opening, before passing between the poles of the electro-magnet. The deviations which were recorded on a photographic plate in the box were the same as before.
Additional experiments showed that the deflections by the magnetic field took place as well when the rays were electrified, after their passage through another magnetic field, as before. Lafay continued the experiments in great detail and by many control tests, and he took accurate measurements and followed the suggestions of others. It would be well for those who have facilities to repeat these most interesting and important researches, to determine for themselves some satisfaction.
It is of interest to note that an American, Paul A. N. Winand, (Mem. Amer. Inst. Elect. Engs.), in the absence of facilities for experimenting, proposed (Elect. World, N.Y., June 6, ’96) to interpose a hollow sphere, which had high potential, in the path of X-rays, and to learn in what manner, if any, the rays are influenced. He argued that it would seem natural that, inasmuch as the rays produce a discharge, there should be a reaction of the charged surface upon the rays.
It is evident that if any one repeats these experiments, expert manipulation is required.
139b. Gouy’s Experiments. The Penetration of Gases into the Glass Walls of Discharge Tubes. Comptes Rendus, March 30, ’96. From trans. by Louis M. Pignolet. From observations with slightly different glass from four tubes, it seemed that the cathode rays cause the gases in the tubes to penetrate the glass where they remain occluded until the glass is nearly softened (after cutting off the current), by heat, whereby they are set at liberty as minute bubbles visible by the microscope, which finally partly combine and become visible to the naked eye.
Halos 1 ft. diam., in clear air, around incandescent electric lamps
of usual size. Cross at center of each halo. [§ 140], p. [143].
Observed by means of a photograph, in 1882, by William J. Hammer.
Mortification of the Ulna. [§ 204].
From sciagraph by Prof Miller.
Under the same conditions, tubes which have been used for a long time exhibit numerous wrinkles, indicating a superficial modification of the glass. These may exist with or without the bubbles.
140. Discharge Tube Surrounded by a Violet Halo. By means of enormous potential and high frequency, the tube was surrounded, Tesla stated, by violet luminosity or halo. [§ 6]. and [74]. From the fact that Lenard obtained a similar appearance in front of the aluminum window, it might be reasonable to conclude that there is some close relationship between the two phenomena.
As an illustration of halo by light, may be mentioned the well known appearance so often occurring in the atmosphere concentrically with the moon, and sometimes surrounding the sun. Under favorable circumstances, (in a mist or dust in the air), a halo, at some distance from a flame or other light is faintly visible. It has generally been assumed that the reason of a halo by light is based upon the laws of reflection, or refraction or both, the bending of the rays taking place, through, or upon the surface of the particles of moisture. Others have held that particles of ice in the upper atmosphere, are the reflectors or refractors, or both. More puzzling has been the attempt to explain the novel appearance reproduced fairly well in the cut, page 140. It is here represented in print for the first time, but the photograph from which it was taken, was at various times, shown to different physicists, some of whom attributed the beautiful effect to the property of interference of light, and naming Newton’s rings as an analogous production. Prof. Anthony in an interview expressed himself as well satisfied that interference could not occur under the circumstances named. He recognized that there was a curved surface of glass which might be considered as made up of an infinite number of layers. The author introduces the matter for the purpose of consideration by others, and especially because it is so intimately connected with the subject of the vacuum tube and electricity. The details must be understood for the purpose of proper appreciation. Mr. William J. Hammer, of New York, had a photograph taken of the large Concert Hall at the Crystal Palace, Sydenham, Eng., by the light of the Edison incandescent lamps with which the Hall was illuminated. This photograph was made in 1882 during the International Electrical Exhibition held at the Crystal Palace. The picture shows a small section of the whole photograph and represents (although probably no one would judge so by looking at the picture) a festoon of pear-shaped incandescent electric lamps, each one hanging downward, and separated from its neighbor by between three and four feet. They were so far away from the camera that a picture of the lamps unlighted, would have represented them as mere specks. The bright circles with the bright central crosses in the centre of the dark spaces were, therefore, fully one foot in diameter, while the lamp bulbs themselves were only about two or three inches thick, as usual. Why then should there be the halos? Why should the crosses appear? And why should the black area be so large? If the electricity and vacuum have nothing to do with it, why should not the halos appear when photographs are taken of flames and other sources of light in the absence of mist and dust? In order to answer questions which will perhaps be proposed, let it be stated that there was no visible dust nor moisture in the room, the photograph being taken early in the evening and at a time when the Hall was not in use. The halos were not apparent except when reproduced by a photograph. The lamps had the usual carbon filaments hanging so that the several filaments were in different planes, and they were of 16 candle power and were connected in parallel circuit, the average E. M. F. being about 110 volts. The lamps were fed by the Edison direct current dynamos. The festoon shown, is one of a dozen or more which were suspended between the columns rising from the gallery and supporting the roof and were hung about forty feet from the floor. The hall was further illuminated by a huge electrolier pendant from the centre of the ceiling. These details were obtained from Mr. Hammer, who planned the installation.
141. Anæsthetic Properties of X-rays.—Tesla reported that he and his assistants tested the action of the rays upon the human system, and found that upon continued impact and penetration of the head by very powerful radiations, strange effects were noticed. He was sure that from this cause a tendency to sleep occurred ([§ 84], at end), and the faculties were benumbed. He said that time seemed to pass quickly. The general effect was of a soothing nature, and the top of the head seemed to feel warm under the influence of the rays. Incidentally, he noticed, as he stated, “When working with highly strained bulbs, I frequently experienced a sudden and sometimes even painful shock in the eye. Such shocks may occur so often that the eye gets inflamed, and one cannot be considered cautious if he abstains from watching the bulb too closely.”
The author calls to mind the reports in the daily press that Edison also noticed that the eyes were in some way sensitive to the rays. The eye, it was reported, became fatigued at the time, and yet later, objects could be more easily distinguished.
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.
Tesla’s Figs. 1 and 2, Reflection and Transmission of X-Rays by Different Substances. [§ 145] and [§ 146a].
The form of tube described by Tesla in full, will hereinafter be alluded to as exhibited in the several figures accompanying this description, and it consisted, therefore, of the long tube “b” made of very thick glass except at the end opposite the electrode “e”, where it was blown thin, p. [149]. The electrode was an aluminum disk having a diameter only slightly less than that of the tube and located about one inch beyond the rather long narrow neck n, into which the leading-in wire c entered. It is important that a wrapping w be provided around this wire, both inside and outside of the tube. The sealing point was on the side of the neck. An electric screen has been referred to heretofore. It is lettered s, and was formed of a coating of bronze paint applied on the glass between the electrode and neck n. The screen could be made in other ways, for example, as shown at s, Fig. [2], where it consists of an annular disk behind and parallel to the electrode disk. This ring s in Fig. [2.] must be placed at the right distance back of the electrode e, but just how far can only be determined by experience. The unique service of the screen was that of an automatic system for preventing the vacuum from becoming too high by use. The peculiar action was as follows, namely from time to time, a spark jumped through the wrapping w within the tube to the screen and liberated just about enough gas to maintain the vacuum at an approximately constant degree. Another way in which he was able to guard against too high a vacuum, consisted in extending the wrapping w to such a distance inside of the tube, that the same became heated sufficiently to liberate occluded gases. As to the long length of the leading-in wire within a long neck behind the cathode, Lenard found the same to be valuable in conjunction with a wrapping around the wire. With high potential, a spark, at a certain high degree of vacuum, formed behind the electrode, and prevented the use of very high potential, but by having the wire extend far into the tube and providing wrappers, the sparking was much less likely to occur. By proper adjustment as before intimated, Tesla could produce just about enough to compensate for the electrical increase of the vacuum. Another difficulty that presented itself in connection with high E. M. F. was the undue formation of streamers heretofore referred to, apparently issuing from the glass, and so often disabling it. He therefore immersed the discharge tube in oil as pointed out in detail hereinafter. The walls of the tube served to throw forward to the thin glass many of those rays that otherwise would have been scattered laterally. Upon comparing a long thick tube of this kind with a spherical one, the sensitive plate was acted upon by the rays in 1/4 the time with the tube. A modification consisted in surrounding a lower portion of the tube, with an outside terminal e, indicated in dotted lines in Fig. [1]. In this way the discharge tube had two terminals. The greatest advantage probably in using a long tube, was that the longer it was, within the proper limits, the greater the potential which could be applied with advantages. As to the aluminum electrode, he noticed that it was superior, in comparison with one made of platinum which gave inferior results, and caused the bulb to become disabled in an inconveniently short period of time.
146. Percentage of Reflected X-rays. He performed some preliminary experiments, testing roughly as to whether any appreciable amount of radiation could be reflected or not from any given surface. Within 45 minutes he was enabled to obtain clear and sharp sciagraphs of metal objects, and the same could have been obtained only by the reflected rays, because he screened the direct rays by means of very thick copper. By a rough calculation he found that the percentage of the total amount of rays reflected was somewhere in the neighborhood of 2 per cent.
Prof. Rood, of Columbia University, N.Y., (Sci., Mar. 27, ’96.) by means of an experiment with platinum foil, [§ 80], concluded that the per centage was about .005, the incident angle being 45 degrees. He regarded this figure as the mere first approximation. Judging from Roentgen, [§ 85], Tesla, Rood and others, therefore, it seems to be established that the percentage of X-rays reflected is very small.
Prof. Mayer, of Stevens Institute, (Science, May 8, ’96,) is of the opinion that there is a regular or specular reflection, having witnessed some experiments obtained by Prof. Rood, of Columbia Univ., N.Y. Prof. Mayer reported that the original negatives were taken in such a way as to substantiate regular reflection, and were carefully examined by six eminent physicists at the National Acad. of Sci. at Washington, April 23, ’96, and none had the slightest doubt concerning the completeness of the demonstration. The material employed for reflecting was platinum foil. [§ 103a].
Difference Between Diffusion and Reflection. Judging from the experiments above related, as well as those considered in [§ 103a], there might at first appear to be contradictory results, reported by different authorities. Experts, it is thought will, without argument, discover the harmonious agreement, and will commend the work of scientists, who, in different parts of the world, and at about the same time, made similar experiments, which now being considered jointly, are found to agree so wonderfully closely. Upon reading the above sections and those referred to, there can be no doubt whatever but that X-rays, upon striking a body are, to a certain per cent. scattered, or thrown back, or bent from their straight course, and sent in a backward and different direction, at one angle or another. The only apparent absolute contradiction to this is that of Perrin, [§ 103a], near the end. But his is a case of one witness against scores, and, therefore, evidence based upon his experiments, must be counted out. The error was either due to some oversight of his own, or more probably the mistake is merely a typographical one, for often a mistake creeps in between a man’s dictation and the printed work. It is difficult to accuse Perrin of a mistake, for he is a great French authority in such matters. Assuming that no error has occured, let it be noticed that he does not pronounce non-reflection from all substances, but only from steel p. [154], l. 9, and flint, which have been so polished as to form a mirror-like surface, whereas all other experimenters, with scarcely an exception, have not employed such surfaces. The difficult point to believe is that, after six hours, no energy from the mirror could be collected. If we accept Perrin’s results it must be only in regard to those two particular materials, polished steel and flint. Another feature which is on the edge of conjecture, is that of true or specular reflection, referred to by Prof. Mayer, [§ 146]. Many attempts have been undertaken to prove whether the rays were thrown backward on the principle of reflection as light from a mirror, or of diffusion as light from chalk. Let the student notice that the evidence is overwhelming in favor of the turning back of the rays to a very small per cent. upon striking any object. As to specular reflection, which means similar to the reflection of light from a polished mirror, it is practically the same as diffusion, the difference being substantially of a technical nature. This allegation is based upon the detail distinction between reflection and diffusion given by P. G. Tait, professor of natural philosophy, Univ. of Edinburgh, who states, in Encyclo. Brit., vol. 141, p. 586:—
“It is by scattered light that non-luminous objects are, in general, made visible. Contrast, for instance, the effect when a ray of sunlight in a dark room falls upon a piece of polished silver, and when it falls on a piece of chalk. Unless there be dust or scratches on the silver, you cannot see it, because no light is given from it from surrounding bodies except in one definite direction, into which (practically) the whole ray of sunlight is diverted. But the chalk sends light to all surrounding bodies, from which any part of its illuminated sides can be seen; and there is no special direction in which it sends a more powerful ray than in others. It is probable that if we could, with sufficient closeness, examine the surface of the chalk, we should find its behavior to be in the nature of reflection, but reflection due to little mirrors inclined to all conceivable aspects, and to all conceivable angles to the incident light. Thus scattering may be looked upon as ultimately due to reflection. When the sea is perfectly calm, we see it in one intolerably bright image of the sun only. But when it is continuously covered with slight ripples, the definite image is broken up, and we have a large surface of the water shining by what is virtually scattered light, though it is really made up of parts each of which is as truly reflected as it was when the surface was flat.”
146a. Reflected and Transmitted X-rays Compared.—In order to carry on a series of investigations, Mr. Tesla constructed a complete special apparatus represented in Fig. [2], p. [149], and embodied in it also an idea which he attributed to Prof. William A. Anthony, which consisted in arranging for sciagraphs to be produced by the rays transmitted through the reflecting substance as well as by the reflected rays themselves. The figure serves to show at a glance the construction and, therefore, the explanation need be but brief. It consisted of a T tube, having three openings, those at the base and side being closed by photographic plates in their opaque holders, which carried on the outside the objects o and o´ to be sciagraphed. At an angle to both plates, and centrally located, was a reflecting plate, r, which could be replaced by plates of different materials. At the upper opening of the plate B was a discharge tube, b, placed in a heavy Bohemian glass tube, t, to direct the scattered rays downward as much as possible from the electrode, e, to and through the thin end of the discharge tube. The objects to be sciagraphed, namely o and o´, were exact duplicates of each other. No statement could be found as to the thickness of the tested plates, r, except that they were all of equal size. The distance from the bottom of the discharge tube to the reflecting plate, r, was 13 inches, and from the latter to each photographic plate about 7 inches, so that both pencils of rays had to travel 20 inches in each instance. One hour was taken as the time of exposure. After a series of experiments with a great many different kinds of metals, they arranged themselves as to their reflecting power, in an order corresponding to Volta’s electric contact series in air. [§ 153]. The most electro-positive metal was the best reflector, and so on. For exhaustive investigations upon the discovery of Volta, see “Experimental Researches” of Kohlrausch, Pogg. Ann., ’53, and Gerland, Pogg. Ann., ’68. The metals Tesla tested were zinc, lead, tin, copper and silver, which were, in their order, less and less reflecting, and the order is the same in the electro-positive series, zinc being the most positive, and the others less and less so, in the order named. For a complete list of the metals arranged by the Volta series, see any standard electrical text-book. He could not notice much difference between the reflecting powers of tin and lead, but he attributed this to an error in the observation.
He tried other metals, but they were either alloys or impure. Those named in the list above were the pure metals. However, he carried on experiments with sheets of many different substances, and arrived at the following table, which shows particularly the relative transmitting and reflecting powers of the various substances in the rough.
Reflecting Body | Impression by Transmitted Rays. | Impression by Reflected Rays. |
|---|---|---|
| Brass | Strong | Fairly good |
| Toolsteel | Barely perceptible | Very feeble |
| Zinc | None | Very strong |
| Aluminum | Very strong | None |
| Copper | None | Fairly strong but much less than zinc |
| Lead | None | Very strong but a little weaker than zinc |
| Silver | Strong, a thin plate being used | Weaker than copper |
| Tin | None | Very strong about like lead |
| Nickel | None | About like copper |
| Lead-glass | Very strong | Feeble |
| Mica | Very strong | Very strong about like lead |
| Ebonite | Strong | About like copper. |
By comparing, as in previous experiments, the intensity of the photographic impression by reflected rays with an equivalent impression due to a direct exposure of the same bulb and at the same distance, that is, by calculations from the times of exposure under assumption that the action upon the plate was proportionate to the time, the following approximate results were obtained:
Reflecting Body | Impression by Direct Action | Impression by Reflected Rays. |
|---|---|---|
| Brass | 100 | 2 |
| Tool steel | 100 | 0.5 |
| Zinc | 100 | 3 |
| Aluminum | 100 | 0 |
| Copper | 100 | 2 |
| Lead | 100 | 2.5 |
| Silver | 100 | 1.75 |
| Tin | 100 | 2.5 |
| Nickel | 100 | 2 |
| Lead-glass | 100 | 1 |
| Mica | 100 | 2.5 |
| Ebonite | 100 | 2 |
He stated that while these figures can be but rough approximations, there is, nevertheless a fair probability that they are correct, in so far as the relative values of the sciagraphic impressions of the various objects by reflected rays are concerned.
In order to devise means for testing the comparative reflecting power in a more decided manner, he laid pieces of different metals side by side upon a lead plate. Consequently the reflecting surface was formed of two parts corresponding to the two metals. [§ 80]. The vertically perpendicular partition of lead served to prevent the mingling of the rays from the two metals. Ingenious precautions were taken; as for example, so arranging matters that upon equal areas of the two plates, equal amounts of X-rays impinged. [§ 80]. He undertook to determine the position of iron in the series by thus comparing it with copper. It was impossible to be sure which metal reflected better. The same regarding tin and lead and also in reference to magnesium and zinc. Here, a difference was noticed, namely that the magnesium was a better reflector.
He has made practical application of the power of the substances to reflect a certain per cent. of the rays by employing reflectors for the purpose of reducing the time required for exposure of the photographic plates. It admits, he stated, of the use of reflectors in combination with a whole set of discharge tubes, whereby rays which would be otherwise scattered in all directions are brought more nearly to a single direction of propagation.
From Sciagraph of Knee-joint. Straight, Front View.
By Prof. Goodspeed. Photo. Times, July, ’96.
It might be argued, that in as much as zinc would reflect only about three per cent. of the incident rays, no practical gain would ensue in sciagraphy by the use of a reflector. He pointed out the falsity of such an argument. In the first place, the angle employed in these tests was 45°. With greater angles, the proportion of reflected rays would be greater assuming that the law of reflection is the same as that of light. By mathematical calculation and tests, he showed that there was no doubt whatever about the advantage of using reflectors. He obtained a sciagraph, on a single plate, of the ribs, arms and shoulder, clearly represented. He stated the details as follows. “A funnel shaped zinc reflector two feet high, with an opening of five inches at the bottom and 23 inches at the top, was used in the experiment. A tube similar in every respect to those previously described, was suspended in the funnel, so that only the static screen of the tube was above the former. The exact distance from the electrode to the sensitive plate was four and one-half feet.”
147. Discharge Tube Placed in Oil.—When the E. M. F. was increased, by having the discharge tube, as usual, in open air, sparks formed behind the electrode, and within the vacuum, and endangered the life of the discharge tube. He obviated this difficulty partly by having the electrode located well within the evacuated space, so that the wire leading to it was unusually long. By excessive E. M. F., also, streamers broke out at the end of the tube. To overcome all difficulties in connection with sparking and breaking of the tube, he followed the proposition of Prof. Trowbridge, and submerged the discharge tube in oil, [§ 11], at end, and [§ 13], which was continually renewed by flowing into and out of the vessel in which the discharge tube was contained, all as shown in the accompanying figure, p. [157], “Discharge Tube Immersed in Oil.” The discharge tube, t, may be recognized by its shape, and it is located horizontally in a cylindrical tube lying sidewise upon a table. To regulate the flow of the oil, the reservoir may be raised and lowered by a bracket, s. The X-rays enter the outside atmosphere by passing first through glass, then oil, and then through a diaphragm of “pergament” forming the right hand end of the oil vessel. When the results were compared with those obtained by Roentgen in his first experiments, the rays were found so powerful that it is not surprising that Tesla was able to obtain more definitely a closer knowledge of the properties of the rays. Roentgen obtained, with his tube and a screen of barium platino cyanide, a shadow picture of the bones of the hand at a distance of less than 7 ft., while Tesla obtained a similar picture with a screen of calcic tungstate, and with his tube immersed in oil at a distance of 45 ft. Tesla also made sciagraphs with but a few minutes’ exposure at a distance of 40 ft., by the help of Prof. Henry’s method, i.e., with the assistance of a fluorescent powder. [§ 151]. He referred also to Salvioni’s suggestion of a fluorescent emulsion. He attributed to Mr. E. R. Hewitt the conjecture that the sharpness of the sciagraphs might be increased by a thin aluminum sheet having parallel groves. Several experiments were made, therefore, with wire gauze, as well as with a screen formed of a mixture of fluorescent and iron-fluorescent powders. With the strong power of the rays as obtained by Tesla in combination with such adjuncts, the shadows were sharper, although the radiation, of course, was weakened by the obstruction. [§ 107b].
Discharge Tube Immersed in Oil, [§ 147], Page [156].
With the apparatus involving the discharge tube in oil, and with tremendously high potential, he obtained what may be called wonderful results; for with the sciascope he obtained shadow pictures of the vertebral column, outline of the hip bones, the location of the heart (and later detected its pulsations), ribs and shorter bones, and, without the least difficulty, the bones of all the limbs. More than this, a sciagraph of the skeleton of the hand was perceived through copper, iron or brass very nearly 1/4 inch thick, while glass 1/2 inch thick scarcely dimmed the fluorescence. The skull of the head of an assistant acted likewise, while at a distance of three feet from the discharge tube. The motion of the hand was detected upon the screen although the rays first passed through one’s body. In making observations with the screen, he advised that experimenters should surround the oil box closely, except at the end, with thick metal plates, to prevent X-rays from coming in undesired directions by reflection from different objects in the room. Obviously the shadows will be sharper.
148. Bodies Not Made Conductors by X-rays. Tesla referred to Prof. J. J. Thomson as having announced some time ago “that all bodies traversed by Roentgen radiations become conductors of electricity.” The author has witnessed other similar expressions giving credit to Thomson in this respect, but he understands that Prof. Thomson, having discovered that X-rays discharge both negatively and positively charged bodies, conjectured or drew a corallary as to the probability of the bodies therefore becoming conductors. Tesla, nevertheless, seems to have proved that the corallary does not hold. In the first place he employed the very powerful rays, and next, he let the oil be the substance traversed by the rays. Besides this, he applied a sensitive resonance test. See detail treatment of his experiments on this subject in Elect. Rev., N.Y., June 24, ’93, p. 228. In brief “a secondary not in very close inductive relation to the primary circuit, was connected to the latter and to the ground, and the vibration through the primary was so adjusted that true resonance took place. As the secondary had a considerable number of turns, very small bodies attached to the free terminal produced considerable variations of potential of the latter. Placing a tube in a box of wood filled with oil and attaching it to the terminal, I adjusted the vibration through the primary so that resonance took place without the bulb radiating Roentgen rays to any appreciable extent. I then changed the conditions so that the bulb became very active in the production of the rays.”
According to the corallary above referred to, the oil should be, with such an environment and under such subjection, a conductor of electricity, but it was not. He emphasized his satisfaction in the results by saying “the method I followed is so delicate that a mistake is almost an impossibility.”
Prof. W. C. Peckham, Elect. World, N.Y., May 30, ’96, reasoned that the oscillating electro-static action upon the outside of the tube, is concerned in the production of fluorescence, and other properties of X-rays. “These oscillations are certainly synchronous with the vibrations of the cathode rays in the tube, which in turn synchronize with the oscillation in the induction coil. If the vibrations of the tube cannot keep time with those of its coil, few or no X-rays will be given out. The cause seems to be similar to that of sympathetic vibrations in sound. In a word, the discharge tube is a resonator for its coil, and when the coil and tube are properly attuned, the maximum effect is obtained.
149. Appleyard’s Experiment. Non-conductors Made Conductors by Current. Proc. Phil. So., May 11, Nature, Lon., May 24, ’64, p. 93. A piece of celluloid was pressed between two metal plates serving as terminals. A galvanometer was employed to indicate the diminution of resistance by time, and it also showed that the electrification was negative. When mercury was one of the metals, the abnormal results did not occur, except to a very small extent. When the celluloid was replaced by gutta percha tissue, the electrification was normal. Many non-metals were employed, and several were lowered in resistance.
149a. Resistance Somewhat Independent of Metal Particles.—Through a mixture of conducting and non-conducting materials, like a sheet of gutta percha, having brass filings imbedded therein,—with 750 volts, no current passed, and this held true until the proportion in weight of the metal to the gutta percha was 2 to 1. Let it be remembered, also, that selenium is reduced as to resistance under the influence of light.
150. Minchin’s Experiment. Resistance Lowered by Electro-magnetic Waves. Nature, Lon., May 24, ’94, p. 93.—Referring to Appleyard’s experiment, it will be noticed that he found that mixtures of certain limited per cents. of metallic particles and insulators were exceedingly high in resistance. Prof. G. M. Minchin found that such materials became conductors under the influence of powerful electro-magnetic disturbances, and that after the current was conducted, its resistance remained greatly lowered in behalf of very weak impulses, although, before the experiment, the resistance was so high. [§ 14a]. But after the current was interrupted by moving the terminal away from the mixture, the high resisting power returned slowly, at a rate somewhat in proportion to the hardness of the mixture. The film employed consisted of shellac or gelatine or sealing wax, while among the metals was pulverized tin. In the latter case, the resistance was reduced by the electro-magnetic waves from apparent infinity to 130 ohms, the electrodes being displaced by 1 cm.
CHAPTER XII
Miscellaneous Researches on Roentgen Rays.
151. Pupin and Swinton’s Experiment. Sciagraphic Plates Combined with Fluorescent Salts. The Elect., Lon., Apr. 24, ’96.—Prof. Pupin, of Columbia College (Electricity, N.Y., Feb. 12, ’96—the author saw him use it Feb. 7, ’96—), was among the first, and probably actually the first, to lessen the time of exposure by a fluorescent screen. Prof. Salvioni also worked in this direction at an early date. Prof. Swinton reported some details in the matter, and he was able to obtain a sciagraph of the bones of the hand in less than 10 seconds, with a moderately excited discharge tube, whereas, without the screen the time was two minutes. He experimented first with barium platino cyanide, but the results referred to were obtained with calcic tungstate, finely ground, and made up into paste by means of gum, and dried. He spread the same upon a celluloid sheet which was placed with the celluloid side against the photographic film. The difficulty experienced first was in the formation of spots on the negative, because some of the crystals fluoresced more than others. Such a defect, however, showed that the fluorescent salt increased the rapidity of the action upon the photographic film. The result of this experiment, as well as that of others, has sufficiently established the fact that the fluorescent screen is of great importance in connection with the art of rapid sciagraphy.
Phosphor sulphide of zinc is among those which hasten photographic action. (Chas. Henry, in Comptes Rendus, Feb. 10, ’96.) Dr. W. J. Morton employed the screen in taking the sciagraph of the thorax, p. [61]. The advantageous use is also confirmed by Basilewski (Comptes Rendus, March 23, ’96. From trans. by Louis M. Pignolet).—The photographic plate was covered with a sheet of paper coated with barium and platino cyanide, so that the two prepared surfaces were in contact, and the fluorescent paper was between the object and the plate.
Thorax. [§ 206].
By W. J. Morton, M.D. Fluorescent screen used ([§ 151]).
Normal Elbow. [§ 204].
By Prof. Miller.
J. W. Gifford, (Nature, May 21, ’96) tried a great variety of fluorescent bodies in combination with the photographic plate, and found that potassium platino cyanide was decidedly the best.
152. Thompson’s (S. P.) Experiment. Penetrating Power of X-rays Varies with the Vacuum. Comptes Rendus. CXIII., p. 809. The Elect., Lon., April 24, ’96, p. 866. In a communication to the Académie des Sciences Prof. Sylvanus P. Thompson of the University College of Liverpool, argued that by one kind of X-rays the bones of the hand were more easily penetrated than by another kind. The two varieties were produced by different vacua. [§ 75] and [76]. Let the vacuum be supposed to become higher and higher. At the first generation of the X-rays, the fluorescent screen showed that the bones of the hand cast very dark shadows. With increase of the vacuum, the shadows of the bones were very faint. This result is also obtained by reduction of temperature. [§ 152a].
152a. Bleekrode’s Experiment. Permeability at Low Temperatures Increased. Elect. Rev., Lon., June 12, ’96.—Experiments performed by him confirmed those of Edison. [§ 135]. An experiment by Prof. Dewar strongly confirmed the results. They noticed the same peculiarity that Edison did, namely, that the shadow of the finger exhibited the flesh and bones as if they were equally transparent. Varied tests showed that the reduction of the temperature of glass increased its permeability.
153. Murray’s Experiment. Reduction of the Contact Potential of Metals by X-rays. Trans. R. So., Mar. 19, ’96. The Elect., Lon., Apr. 24, ’96, p. 857. J. R. E. Murray of the Cavendish Laboratory, at the suggestion of Prof. J. J. Thomson, carried on a long series of careful experiments, to find whether the contact potential of a pair of plates of different metals was, in any way, affected by the passage of X-rays between the plates. All the ordinary precautions were taken. The contact potential was measured by Thomson’s (Kelvin) method, see Trans. Brit. Asso., 1880. The important result obtained, was that “the air through which the rays pass, [§ 90], is temporarily converted into an electrolyte, [§ 47], and when in this condition forms a connection between the plates, which has the same properties as a drop of acidulated water, namely, it rapidly reduces the potential between the opposing surfaces of the plates to zero, and may even reverse it to a small extent.”
154. Nodon’s Experiment. Transparency of Differently Colored Media to the X-rays. Comptes Rendus, Feb. 3, ’96. From trans. by Louis M. Pignolet. The rays were passed through two openings in a thick metal diaphragm, one of which was covered by an uncolored piece of gelatine and the other by a piece tinted with the color to be tested. The two images were received on the same plate. The various colors tested were traversed with equal facility by the rays, [§ 68] and [82].
The investigation described above was made by Albert Nodon at the Laboratoire des Recherches Physiques à la Sorbonne.
This agrees with Bleunard who found that colors seemed to have no influence on the passage of the rays as water colored with various aniline colors offered no more resistance than when pure. From trans. by L. M. P. Comptes Rendus, March, ’96.
A. and L. Lumière (Comptes Rendus, Feb. 17, ’96,) observed that the X-rays act in the same manner upon colored photographic plates rendered sensitive to various regions of the spectrum. Thus, plates sensitive to red, yellow and green gave exactly the same impression, provided they had the same general sensibility to white light. While this may not be accurately so, it illustrates that materials are penetrated by X-rays independently of the laws of color.
155. Meslans. Chlorine, Iodine, Sulphur, Phosphorus, combined with Certain Compounds, Increase Opacity to the X-rays (Comptes Rendus, Feb. 10, ’96. From trans. by Louis M. Pignolet.)—Carbon in its various forms was found to be very transparent, also organic substances containing, besides carbon, only the gaseous elements hydrogen, oxygen and nitrogen; but this transparency was far from uniform. Organic substances,—ethers, acids, nitrogenized compounds (corps azotes),—were easily traversed by the rays; but the introduction of an inorganic element, as particularly, chlorine, sulphur, phosphorus, and, above all, iodine, renders them opaque. [§ 82]. This occurs also with sulphates of the alkaloids. Iodoform, the alkaloids, picric acid, fuchsine and urea are very transparent. Metallic salts are very opaque, but this varies with the metal and the acid. Bleunard went further into details. The opacity of solutions of salts increased with the atomic weight of the metal and of the metalloid. Water was easily traversed by the rays. Solutions of bromide of potassium, chloride of antimony, bichromate of potash offered considerable opposition to the passage of the rays. Solutions of borate of soda, permanganate of potassium were easily traversed. The liquids were held in paper boxes. The experiments above related were conducted by Maurice Meslans at l’École de Pharmacie de Nancy.
From Sciagraph of Pencil, Key, Fountain-pen, and Coin. [§ 161].
By Prof. McKay, Packer Institute.
From Sciagraph by Prof. Miller. [§ 156].
1. Real diamond.
2. Paste.
3. Glass.
4. Real diamond mounted in gold ring.
156. Buquet & Gascard’s Experiments. Action of the X-rays upon the Diamond and Its Imitations; also upon Jet. Comptes Rendus, Feb. 24, 96. From trans. by Louis M. Pignolet.—Sciagraphs taken by the X-rays showed that diamonds became transparent, and their shadows disappeared with long exposures; but imitation diamonds remained opaque under the same conditions. Jet was distinguished from its imitations by the same method. The diamond and jet cast clearer shadows on a fluorescent screen than their imitations.
The above tests were made by Albert Buquet and Albert Gascard, at the Cabinet de Physique de l’École des Sciences de Rouen.
The half-tone on lower half of adjacent page, 164, was taken from a sciagraph by Prof. Dayton C. Miller, of Case School of Applied Science. The differences of opacity are proved, because all were of same thickness and exposed simultaneously.
Prof. Sylvanus P. Thompson (The Elect., Lon., May 18, ’96) confirmed the above, and also found that, although the diamond is more transparent than glass, it is more opaque than block carbon or graphite.
Mineralogists are thus enabled to submit minerals to the X-ray test in making analyses.
157. Dufour’s Experiment. Inactive Discharge Tubes made Luminous by X-rays. Comptes Rendus, Feb. 24, ’96. From trans. by Mr. Pignolet.—He observed that very small and sensitive Geissler tubes phosphoresced when exposed to X-rays. [§ § 22], [23].
158. Beaulard’s Experiments. Non-Refraction of X-rays in a Vacuum. Comptes Rendus, Mar. 30, ’96. From trans. by Louis M. Pignolet. With prisms of ebonite, F. Beaulard held that no decided deviation could be observed within the vacuum.
159. Carpentier’s Experiment. Sciagraph Showing the Parts in Relief on a Coin. Comptes Rendus, Mar. 2, ’96. From trans. by Louis M. Pignolet. An imprint of a coin stamped upon a thin piece of well annealed aluminum by pressing the coin against the aluminum, was reproduced in a sciagraph. The raised parts of the coin were scarcely 8/100 of a millimeter high. The aluminum was 5/10 millimeter thick. This result is admirably represented by the sciagraph of an aluminum medal on page 166, taken by Prof. Dayton C. Miller, of Case School of Applied Science, Elect. World, N.Y., Mar. 21, ’96, who also made a sciagraph of a copper plate 1/4 inch thick having blow holes which appeared in the picture, but they could not be detected by light, serving to illustrate an application of the new discovery in testing the homogeneity of metals.
160. Wuillomenet’s Experiments. Transparency of the Eye to the X-rays Determined by Sciagraph of Bullet Therein. Comptes Rendus, Mar. 23, ’96. A sciagraph taken with an exposure of three hours showed perfectly a lead shot introduced into the vitreous media of the eye of a full grown rabbit. Therefore the opacity of the media of the eye was not absolute.
In a second series of experiments by Dr. Wuillomenet a human head was used, but the results were negative in spite of a great intensity of the rays and a long exposure, [§ 82].
161. Fernand Ranwez’s Experiments. Application of the X-rays to Analysis of Vegetable Matter. Comptes Rendus, Apr. 13, ’96. From trans. by Louis M. Pignolet. Sciagraphy can render valuable services in analytical researches and specially in the analysis of vegetable foods where they will show the most usual adulterations consisting of mineral substances.
Bas-relief Sciagraph, [§ 159], by Prof. Dayton C. Miller.
This method offers several advantages for small samples of the substances can be examined. The samples are not chemically changed. A great number of tests can be made in a short time. Lastly, the sciagraph obtained affords a permanent record.
The tests were made on samples of adulterated saffron composed of mixtures of pure saffron and saffron coated with sulphate of barium. A sciagraph taken with an exposure of three minutes showed scarcely visible imprints of the pure but strong impressions of the adulterated. See sciagraph of pen, (mineral) in holder, (vegetable), in cut at upper part of p. [164], which also shows the graphite in a wooden pencil.
162. Errera’s Experiment. Action of the X-rays on Phycomyces. Hertz Waves and Roentgen Rays Not Identical. Comptes Rendus, March 30, ’96. From trans. by Louis M. Pignolet.—Phycomyces Nitens, when submitted to the asymmetrical action of Hertz electric waves, became curved, according to Hegler. Errera found a Phycomyces was not affected by the X-rays, thus denoting an absence of Hertz waves in the rays. Credit for the above result is due to L. Errera, from experiments made at the Laboratoire Physique and the l’Institut Solvay (Université de Bruxelles).
163. Gossart, Chevallier, Foutana and Uruanni’s Experiment, in Conjunction with J. R. Rydberg. No Mechanical Action of X-rays. Comptes Rendus, Feb. 10, Mar. 23, Apr. 13, ’96. From trans. by Louis M. Pignolet.—The former party alleged that radiations from a discharge tube caused a cessation of the rotation of the vane of the radiometer. J. A. Rydberg was not inclined to confirm such action. A. Foutana and A. Uruanni made experiments and concluded that the action was due to an electro-static force, having noticed that a Leyden jar would also produce such effect. The author made some experiments to determine the matter in reference to X-rays at a distance outside of the electro-static field. The rays would neither stop the vanes nor cause them to rotate. He made some other experiments to detect whether there was any direct mechanical power possessed by the rays; but if any, it was exceedingly feeble.
T. C. Porter made some experiments at Eton College, (Nature, June 18, ’96,) which confirmed the above results, finding that the radiometer is entirely inert to the Roentgen rays, whether they be from a properly electrically screened hot or cold tube. He distinguished between the caloric conditions, for he found that, not only will reduction of temperature vary the penetrating power of the rays, [§ 135] and [152a], but also will an increase of temperature.
164. Battelli’s Experiment. X-Rays Within Discharge Tube. Nuovo Cimento, Apr., ’96, p. 193; Elect. Rev., Lon., June 12, ’96.—Shortly after the announcement of the discoveries of Lenard and Roentgen, it would have been considered strange to assert that X-rays may exist inside of the discharge tube. Battelli certainly correctly infers, that inasmuch as X-rays apparently originate from the point where a material object is struck by the cathode rays, [§ 115], it would follow that when the said object is within the vacuum space, X-rays are propagated before they reach the glass wall of the discharge tube. It has already been noted (DeMetz, [§ 63a]) that photographic action may be produced within the discharge tube. Battelli has confirmed this, not by a crude experiment, like that (failure) of some authority in England, but by a series of severe tests, leaving no doubt as to the production of photographic action. He discovered in connection with several subordinate phenomena that among the rays capable of producing a photographic impression within the discharge tube, some were deflected by a magnet and others were not, from which he concluded that X-rays may exist inside the tube, in conjunction with cathode rays, before collision with the anti-cathode. The experiment consisted in deflecting the rays by a magnet, the film being in the path that the rays would have had without a magnet. There was also a film in the path of the deflected rays. Photographic action was produced upon both. He varied the vacuum. Photographic action began at 3-10 mm., had its maximum at 1-70 mm., after which it remained constant. No photographic action was obtained upon a film placed within the tube opposite the anode, except in one case where it was exceedingly weak. Lenard continually inferred that there must be two kinds of cathode rays. [§ 75]. Battelli has certainly sifted the two rays apart and thus proved Lenard’s conjectures. [§ 61b], p. [47]. The Elect. Rev., Lon., pays tribute to Battelli, by offering the following opinion: “We have no hesitation in saying that Battelli, by means of interesting and ingenious experiments, has made the greatest advances in the theory of the X-rays since their discovery by Roentgen.”
In many cases the author has omitted stating, in taking sciagraphs, that the films were protected from ordinary light by opaque material. This, as a matter of course, has always been understood. Battelli also had the films wrapped in material opaque to ordinary light. Experimenters should, if possible, always employ aluminum for this purpose, because the author has always noticed that black paper or cloth permits a great deal of light to come through, even when in double thickness.
Prof. Sylvanus P. Thompson (The Electr., Lon., June 26, ’96) located a wire in a focus tube in the path of the rays between the platinum reflector and the wall of the tube. Not only was there a sciagraph of this wire produced in the sciascope, but also the Crookesian shadow of the wire on the wall of the bulb. For this experiment the exhaustion must be quite high. “At no state of exhaustion did the platinum reflector convert all the internal cathode rays into X-rays.” Both shadows were cast by the platinum reflector as the origin. More or less of the rays between the reflector and the glass were sensitive to a magnet.
Bleyer’s Experiment. [§ 165].
Combined camera and sciascope at the left: and showing induction coil and discharge-tube at the right.
165. Bleyer’s Experiment. Combined Camera and Sciascope. Elect. Eng., July 1, ’96; Royal Acad. Med. & Sur., of Naples, Italy.—As early as April 7, J. Mount Bleyer, M.D., of Naples, constructed and used the apparatus shown in the adjacent cut, p. [169]. The picture is self-explanatory. Attached to an ordinary camera is a flaring sciascope, for receiving the temporary sciagraph of the hand, for example. The X-rays are converted into luminous rays by the fluorescent screen, and, therefore, the camera will serve to take a picture by means of the luminous rays from the sciagraph of the hand. The cut represents also an induction coil and a discharge tube. Soon afterwards, it was reported by an English paper that Dr. Levy, of Berlin, and others of England, had also made similar tests with success. In order to illustrate the applicability of the combination, Dr. Bleyer took many sciagraphs with the camera. He calls it the photofluoroscope, which, however, will probably not meet with favor for the name does not suggest the nature of the instrument. When two radically different devices are combined into one, it is difficult to formulate an acceptable single word, and, therefore, the instrument will probably always be called by some of the following terms: A camera with sciascopic adjustment, or combined sciascope and camera, or corresponding combinations with the word fluoroscope.
From the time that Roentgen’s discovery was announced, scientists throughout the world have made careful experiments, up to date, in all possible directions, and the time has now come when the number of experiments is rapidly decreasing, only one or two being noted now and then in the scientific press, and consisting mostly in repetition, with occasionally a slight departure, involving a radically new subordinate discovery; but in view of the great number of scientists, and of their high standing as careful experimenters, and because also of their desire to be correct in their inferences, there might seem to be little else to be investigated. Time only will tell. Before passing to the final chapters relating to other matters, a few more experiments are related in the briefest manner.
166. Prof. Sylvanus P. Thompson confirmed non-polarization, (Phil. So., June 12, ’96, and The Electr., Lon., June 26, ’96.)
Dr. John Macintyre (Nature, June 24, ’96) carried on a long series of experiments with tourmaline, and also arrived at the conclusion that polarization of X-rays is practically impossible, [§ 97], at end.
From Sciagraph by Prof. Goodspeed, showing Curvature of the Radius, due to Arrested Development of the Ulna at its Distal Epiphysis. One Bone shown through another.
167. In the same paper Prof. Thompson showed conclusively that there is a diffuse reflection of X-rays. [§ 81] and [103]. A curious experiment consisted in his obtaining dust figures, [§ 36]. by the discharge of an electrified body by X-rays. In another experiment he caused reflection of the rays from the surface of sodium located in a vacuum. The amount reflected was a minimum for normal incidence and increased at oblique incidence.
168. Prof. Oliver J. Lodge, F.R.S., reported in The Electr., Lon., June 5, ’96, further detail experiments in the line set out in [§ 113]. He proved conclusively, as stated by the editorial in The Electrician, that a positive charge has increasing effect upon the ray-emitting power of the surface exposed to the cathodic radiation.
169. At Eton College, T. C. Porter (Nature, June 18, ’96) confirmed the experiments of others by showing that the blackened face of the thermopile connected with a very sensitive galvanometer was not influenced in any manner by X-rays.
170. Prof. William F. Magie, of Princeton, N. J., made a careful experiment in relation to diffraction. Princeton College Bulletin, May, ’96. The experiment would certainly prove that if X-rays are due to vibrations, the latter are of a different order from those occurring in light rays, for the slits exhibited light diffraction very well, but there was no evidence, by a widening of the image on the plate, that X-rays had been diffracted in the slightest degree. [§ 110] and [110a].
171. Prof. Haga, of Groningen University, at the suggestion of Mr. J. W. Giltay, (Nature, June 4, ’96,) made some very crucial tests, with numerous precautions, in reference to the action of X-rays upon selenium, and the results were so positive that they thought that a practical application could be made by using selenium for detecting X-rays, both qualitatively and quantitatively. In repeating the experiments, it must be borne in mind that one half hour or so is required for selenium to return to its former degree of ohmic resistance after being struck by light or heat or X-rays.
Total number of § § to this place, 199.
CHAPTER XIII
A few Typical Applications of X-rays in Anatomy, Surgery, Diagnosis, etc.
200. Hogarth’s Experiment. Needle Located by X-rays and Removed. The Lancet, Lon., Mar. 28, ’96.—Dr. Hogarth is the medical officer of the general hospital, Nottingham. A young woman was suffering with a pain in her hand near the metacarpal bone of the ring finger. A slight swelling existed. Ten weeks before, a needle had entered the palm while washing the floor. It had entered at the base of the fifth metacarpal bone. Chloroform had been given and an incision made, but no needle found and its presence doubted. A sciagraph was taken and the needle was accurately located and the next day removed.
201. Savary’s Experiment. Needle Located by Sciascope and Removed. The Lancet, Mar. 28, ’96.—Dr. Savary located a needle by a sciascope although efforts by all other methods had failed. A line was drawn between two points intersecting the needle at right angles. About half an inch below the surface of the skin of the wrist the blade of the scalpel impinged upon the needle, which was removed without difficulty.
202. Renton & Somerville’s Experiment. Diagnosis. The Lancet, Lon., Apr. 4, ’96.—A writer for the Lancet reported that Drs. Renton and Somerville made a diagnosis with the assistance of the screen. In one, the suspected case of unreduced dislocation of the phalanx, they saw that the parts were in the proper position. He showed to medical men an old fracture of the forearm where the fragments of the bones were distinct as to the shadows.
From Sciagraph of “Colles’ Fracture” in the Right Wrist, by a Fall on the Sidewalk. [§ 207].
By William J. Morton, M.D.
203. Miller’s Experiments. Location of Bullets. Elect. World, Mar. 21, ’96.—Bullets were clearly located in the hands of two different men by Prof. Dayton C. Miller, of the Case School of Applied Science. In one, the bullet had been lodged for 14 years and had always been thought to lie between the bones of the forearm, but two sciagraphs from different directions located the ball at the base of the little finger. By means of five sciagraphs from different directions, the ball in the other hand was located at the base of the thumb.
204. Injuries by Accident and Miscellaneous Cases. The Integral, Cleveland, Ohio, ’96.—Many fingers and hands were examined by Prof. Miller that had been injured by planing machines, cog-wheels, base balls, pistols, etc., and in each case the nature of the injuries was determined. Several cases of fractured arms were studied—some through splints and bandages. Some sciagraphs indicated that the ends of the broken bones had not been placed in apposition. Subsequently, an operation was performed to remedy the setting. In one case, he sciagraphed the arm from which a piece of the ulna had been removed five years previously. The necrosis had increased. Two sciagraphs at right angles to each other clearly exhibited the nature of the disease. The permanent set of the toes by wearing pointed shoes was clearly exhibited (p. [30].) The figure on page [147] is the side view of a foot in a laced shoe. The outlines of the bones can be traced, also the eyelets and the pegs in the heel, while the uppers scarcely appear. In Fig. [1] (introduction) is shown a head, only the skull being clearly reproduced. In the negative, the teeth appear and places whence the teeth have been extracted, also the jaw bones, nasal cavities and the ragged junction of the bones and cartilage. The varying thickness is represented in the cut, at the temples and ears. Fig. [2] (introduction) shows that a broken bone was badly set, the ends overlapping each other instead of meeting end to end. A sciagraph of an elbow is shown on p. [161]. The flesh is scarcely visible. Fig. [3] (introduction) is a picture which reproduced the mere indication of the spine and ribs. In the original negative the collar bones, pelvis, clavicles, buckle of clothing and location of the heart and stomach were faintly outlined. Fig. [4] (introduction) is a representation of the knee of a boy 15 years old, in knickerbockers, showing the buttons clearly, and dimly a 32 caliber bullet which is imbedded in the end of the femur.
204a. Necrosis. Mortification of the ulna is represented on p. [142]. Necrosis of the bone corresponds to gangrene of the soft parts; life is extinct.
205. Morton’s Experiment. Diagnosis. Elect. Eng., N.Y., June 17, ’96. Lect. before Odontological So., N.Y., Apr. 24, ’96; repeated in Dental Cosmos, June, ’96.—Dr. William J. Morton, of New York, made several important examinations of the human system by the use of X-rays.
In regard to application in dentistry, he stated:—“Each errant fang is distinctly placed, however deeply imbedded within its alveolar socket; teeth before their eruption stand forth in plain view; an unsuspected exostosis is revealed; a pocket of necrosis, of suppuration, or of tuberculosis is revealed in its exact outlines; the extent and area and location of metallic fillings are sharply delineated, whether above or below the alveolar line. Most interesting is the fact that the pulp-chamber is beautifully outlined, and that erosions and enlargements may be readily detected.”
206. The author saw one of Dr. Morton’s original photographed sciagraphs of the thorax, 15 inches by 11 inches, not at all creditably reproduced at page [161]. In the original, to the surgeon’s eye: “The acromion and coracoid processes of the shoulder blade are clearly shown in their relations to the head of the humerus, or arm bone, and also the end of the clavicle, or collar bone, is shown in its relations to the shoulder joint. We have, in short, an inner inspection in a living person of this rather complicated joint, the shoulder, and there can be no doubt that in defined pictures of this nature even very slight deformities and diseases would be detected. It is noticeable that the front portions of the ribs are not shown, only the posterior portions lying nearest to the sensitized plate appear; also the breastbone was sufficiently dense to almost entirely obstruct the X-rays. A collar button at the back of the neck is taken through the backbone. In some of my negatives the dark outline of the heart and liver is shown as well as the outlines of tumors in the brain; but this is evidently for purposes of demonstrating the location of organs, an over-exposure, and does not, therefore, indicate the outlines of the heart.”
The time of exposure was reduced by the use of a fluorescent screen in conjunction with the photographic plate.
207. A woman was troubled with a stiffened wrist. Dr. Morton took a single sciagraph of both wrists side by side as shown at page [174], (the photographic print being presented for this book by E. B. Meyrowitz, 104 East 23d Street, N.Y.) The injured wrist in the picture exhibited the Colles’ Fracture—the ulna and radius bones being telescoped into their fractured ends by a fall upon the sidewalk a year before. By knowing the cause, the manner of cure became evident, and, accordingly, the patient is expected to bend the wrist backward and forward and laterally several times a day.
From sciagraph of club foot of child by Prof. Goodspeed. Copyright, ’96, by William Beverley Harison, Pub. of X-ray pictures, New York. This linograph (woodcut), engraved and donated by Stephen J. Cox, Downing Building, 108 Fulton St., New York, affords an exact likeness of the sciagraph,—well-nigh impossible by an untouched half-tone.
Dr. Morton, in a lecture before the Medical Society of the County of New York, to be printed in the Medical Record, related that another promising field of research and application is in the detection of calcareous infiltrations involving, for instance, the arteries, or occurring in the lungs and other tissues. Calculi in kidneys, in the bladder, in the salivary ducts have already been successfully located. The stages of ossification, and the epiphyseal relations of the osseous structure in children may be pictured as is demonstrated in the picture of the entire skeleton of an infant five months of age. The sciagraph shows plainly that it will be possible to detect spinal diseases, either in children or in adults. (Not reproduced.)
208. Norton’s Experiment. Diagnosis. Elect. World, N.Y., May 23, ’96.—In conjunction with Dr. Francis H. Williams, Dr. Norton examined several patients from the city hospital to determine how an X-ray diagnosis would agree with that previously made by the hospital staff. (See also [§ 142], at end.) The outline of an enlarged liver, 7 inches in diameter, was easily distinguished, the two outlines, one by percussion and one by X-rays, agreeing better in favor of the latter by 1/2 inch. An enlarged spleen was perfectly outlined. The tuberculosis of one lung caused it to be more opaque than the sound lung. It was found necessary to take into account the seams of clothing, buttons, buckles, etc. A bullet was found exactly under the spot which they marked as being over the bullet. A foreign metallic body can be easily detected in the œsophagus, because the latter is quite transparent. They could see the shadows of the cartilaginous rings in the trachea, glottis, and epiglottis. Younger persons, up to 10 years of age, are more transparent than older.
209. Lannelongue, Barthelemy and Oudin’s Experiments. Osteomyelitis Distinguished from Periostitis. Elec. Rev., Lon., Feb. 14, ’96.—In a sciagraph of a person diseased with the former, the surface of the bone was proved to be intact, while the internal parts were destroyed. In the latter disease the changes proceed from the surface to the interior.
The art of sciagraphy, more nearly, as every month passes, becomes developed by means of improved apparatus, screens, photographic plates and other elements which at present are only dimly predicted. Nevertheless, how can a better sciagraph of bones, showing their thickness and porosity, be desired than that reproduced on page [177], and taken by Prof. Arthur W. Goodspeed, and representing a club foot of a child? In the race to excel in this new art, no one, to the author’s knowledge, has surpassed Prof. Goodspeed, of the University of Penn., considered jointly from the standpoints of priority, superiority, quantity and variety. Dr. Keen, L.L.D., Professor in the Jefferson Medical College, of Philadelphia, stated (Inter. Nat. Med. Mag., June, ’96) that Prof. Goodspeed “has far eclipsed all others in these most beautifully clear sciagraphs.”
210. A book could be filled with the numerous cases of diagnosis by X-rays showing the utility. In closing this chapter, let it suffice to mention some of the sources of literature relating to this subject directly or indirectly: location of shot (by Dr. Ashhurst, Phila.) in lady’s wrist, not located by other means. Dr. Packard’s case of acromegaly; Dr. Muller’s (Germantown) location of needle in boy’s foot; cause of pain not before known; needle subsequently removed; a perfect thorax, or trunk, by Prof. Arthur W. Goodspeed, University of Pennsylvania; Thomas G. Morton’s (M. D. Pres. Acad. Surg., Phila.) application to painful affection of the foot, called metatarsaligia. All of the above noticed in Inter. Med. Mag., June, 1896. Case of a burned hand with anchylosis of the fingers, by W. W. Keen, M.D., L.L.D. Bacteria not killed by X-rays. Normal and abnormal phalanx distinguished. Fracture and dislocation sometimes differentiated by X-rays. Amer. Jour. Med. Sci., Mar., ’96.
CHAPTER XIV
Theoretical Considerations.
Before attempting to discuss the facts now known in regard to the Roentgen phenomena, it is well to review briefly the known ways in which radiant energy may be transmitted.
By radiant energy is, of course, meant energy proceeding outward from a source and producing effects at some distant point. There are two well understood ways in which energy may be transmitted,—first, by an actual transfer to the distant point of matter to which the energy has been imparted from the source, as in the flight of a common ball, a bullet, or a charge of shot. In this mode of transmission, it is evident that the flying particles, assuming that they are subject to no forces on the way, will move in straight lines from the source to the distant point. They constitute real rays, diverging from the source; an obstacle in their path, would, if the radiations proceeded from a point, cast a shadow with sharply defined edges.
Second,—by a transfer of the energy from part to part of an intervening medium, each part as it receives the energy, transmitting it at once to the parts around it, no part undergoing more than a slight displacement from its normal position. This mode of transmission constitutes wave motion. The source imparts its energy to the particles of the medium near it. Each of those particles transfers its energy to the particles all around it. Each of these particles in turn transfers its energy to the particles around it, and so on through the medium. It is plain that there are here no such things as genuine rays. As the energy is transferred from particle to particle, each in turn becomes a centre of disturbance transmitting its motion in all directions. It is only because the movements transmitted from different points annul one another except along certain lines, that we have apparent straight lines of transmission, and, therefore, fairly sharp shadows. But shadows produced by wave transmissions are never absolutely sharp. The wave movement is always propagated to some extent within the boundary of the geometrical shadow, less as the wave lengths are shorter. With sound waves whose lengths are measured in inches or feet, the penetration into the shadow is considerable. With light waves 1/37000 to 1/70000 of an inch in length, the penetration into the shadow is very small and requires specially arranged apparatus to show that it exists.
This penetration into the geometrical shadow is characteristic of energy propagated by wave motion, and if the fact of such penetration can be demonstrated, it is conclusive proof of propagation by waves.
Another characteristic of wave motion is found in the phenomena of interference. This is the mutual effect of two wave systems, which, when meeting at a given point, may strengthen or annul each other according to the conditions under which they meet. Either of those characteristics should enable us to distinguish between propagation by wave motion and by projected particles. But when wave lengths are very short and radiations feeble, the tests are not easy to apply.
Again, a wave is in general propagated with different velocities in different media. This causes a deflection or deformation of the wave as it passes from one medium into another, and results in refraction, as in the cases of light and sound. Absence of refraction would be strong though not conclusive evidence against a wave theory of propagation.
In wave propagation, each particle of the medium suffers a small displacement from its equilibrium position and performs a periodic motion about that position. This displacement may be in the line of propagation—longitudinal vibration—or it may be in a plane at right angles to that line—transverse vibration. All the phenomena mentioned above, diffraction, interference, refraction, and also reflection, belong equally to either mode of wave propagation. Other phenomena must be made use of to distinguish between these.
When the vibrations are transverse they may all be brought into one plane through the line of propagation. They may be polarized, when the ray will present different phenomena upon different sides. When the vibrations are longitudinal, no such phenomena can be produced. Polarization, then, serves to distinguish between longitudinal and transverse vibrations.
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.
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].
An experiment by La Fay ([§ 139a]) seems to show that X-rays, in air, after passing through a charged silver leaf, acquire the property of being deflected by a magnet, as are the cathode rays inside the generating or exhausted observing tube, [§ 72a]. If this is confirmed, it would go far to support the theory that these rays are streams of something.
From Sciagraph of Head by Prof. Goodspeed. Nasal Bones appear like Eyelashes.
Inter. Med. Mag., June, ’96.
The cervical vertebræ are distinguishable in the original, but barely so in the half-tone. Fillings are located.
The burden of proof, up to the present, seems to be against any wave theory of the X-rays, for, although they are like the ultra-violet rays in producing fluorescence and in affecting the photographic plate, and have some points of similarity to these rays in their effect upon charged bodies, the X-rays are totally unlike the ultra-violet, in respect to diffraction and interference phenomena. In fact, the absence of such phenomena, if they are really absent, is conclusive proof that the X-rays cannot be wave motions, unless of a wave length extremely short even as compared to waves of light.
Since writing the above, I have seen an account of experiments in relation to diffraction of X-rays, presented to the French Academy by MM. L. Calmette and G. T. Huillier, in which the authors claim to have obtained evidence that diffraction occurs. The following translation of MM. Calmette and Huillier’s paper is taken from the Electrical Engineer, N.Y., for July 22, 1896.
“We have the honor of submitting to the Academy some photographic proofs obtained with the Röntgen rays by means of the following arrangement.”
“Very near the Crookes tube there is a screen “E” (diagram omitted), of brass, perforated by a slit, the width of which has rarely reached a half mm. A second metal screen, E´, is formed of a plate provided with two slits or pierced with a window in which is fixed a metal rod of 1 mm. in diameter. This screen is placed at the distance, a, behind the former. Lastly, a photographic plate, enfolded in two leaves of black paper, is placed at the distance, b, behind the second screen, E´.”
“The following table indicates, for each proof, what is the screen E´ used, and the value of a and b + a:
E´.
| No. | a Cm. | b + a Cm. | |
|---|---|---|---|
| 1. | Rod of 1 mm. in diameter | 5 | 19.5 |
| 3. | Rod of 1 mm. in diameter | 5.5 | 20 |
| 5. | Rod of 1 mm. in diameter | 8.9 | 30 |
| 7. | Two narrow slits, separated by a cylindrical rod of 1 mm. in diameter | ? | ? |
“On the proofs 1, 3, 5 the shadow thrown by the metallic rod is bordered on each side by a light band which shows a maximum of intensity. Within this shade we observe a zone less dark, which seems to indicate that the Röntgen rays penetrate into the geometrical shadow. Lastly, in proofs 3 and 5 we see, in like manner, a maximum of intensity along the margins of the window in which the rod is placed.”
“In the proof No. 7 we perceive, in the middle of the two white bands, a fine dark ray, while in the shadow of the rod which separates the two slits there is seen a light ray.”
“If we compare these results with those obtained with light in the same conditions, the slit being relatively wide and the intensity weak, it seems difficult not to ascribe them to the diffraction of the Röntgen rays.”
“The proofs obtained in these experiments—which we propose to continue—are not yet so distinct that we can measure the wave length with any precision. But we are still led to believe that this wave length is greater than that of the luminous rays.—Comptes Rendus.” Of course, if diffraction phenomena can be demonstrated, the question as to the radiations being wave propagations, is settled, though the question whether the vibrations are longitudinal or transverse, is still open.
Before accepting any stream or vortex motion theory, we need to know more about the X-ray phenomena, and more about stream and vortex motion.
- Transcriber’s Notes:
- Since this is a collection of articles by different scientists, there may be differences in spelling and usage.
- There is no experiment 64. There last experiment on page [51] is number 63b, and the first experiment page [52] is 65. (A note attached to the 63b table of contents entry says that there is no experiment 64.)
- The missing entries in the Table of Contents for experiments 128a and 149a were added.
- There are two experiments labeled 61b, page [46] (Thomson’s Experiment) and [47] (Perrin’s Experiment). The instance on page [47] was relabeled 61c.
- There are two experiments numbered 159 in the Table of Contents. The first follows entry 110a and the other is in order, after experiment 158. The first instance was changed to 159a.
- Missing or obscured punctuation was silently corrected.
- Typographical errors were silently corrected.
- Inconsistent spelling and hyphenation were made consistent only when a predominant form was found in this book.