Letter: Tesla On The Roentgen Streams

Wednesday, December 2, 1896
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December 2- 1396 ELECTRICAL REVIEW l[Sil llll THE Hlllllllilll Slll[lMS. To 'ras Eorroa or Erxcrnrcsn Rxvnw: The following lines may contain some useful information for physicists and physicians. Those who, in the exercise of their professional duties, are applying the discoveries of Roentgen to the relief of the suffering by deter- mining the position of foreign objects or ascertaining the condition of local troubles or malformations' in the organism, are apt to be disappointtd in many instances. While it is per- fectly easy to tind the position of a. foreign object in the head, neck and all soft tissues of the body,and detect some far gone trouble in the lungs, often the location of even such a large and opaque object as a bullet, when imbedded in certain bony parts ofthe trunk of the patient, may be attended with difficulties. Success will be invariably attained if the suggestions which are given below, and which are the outcome of a number of observa- tions of such cases, are strictly fol- lowed. In order to make the present state- ments self-contained and more useful, I deem it of advantage to say a few words in regard to the Roentgen rays. According to all evidences so far obtained by me, I entertain the view, which I have expressed on other occasions, that these rays are formed by streams of some matter projected with great velocity, and generally intermittently, from the walls of the tube. The intermittent character is only due to this feature of the appa- ratus usually employed for the produc- tion ofthe rays; but the oscillatory or intermittent discharge is not abso- lutely necessary, as I have produced unidirectional currents of high tension which are likewise capablefof generat- ing : strong rays, and as a static machine may be used with a like result. The mode of formation of these rays or streams is, for the present purposes, of little impor- tance. The small particles within the bulb, which are the original cause, may be ions, formed by a process of electrolysis, or they may be compara- tivelylarger particles of the electrode, or perhaps molecules of the residual gas. At any rate, it is probable that the particles are very minute, and that, therefore, the velocities of the cathodic streams within the vessel are such and the impacts so violent as to cause a further disintegration of the cathodic matter to a stats prob- ably never before studied by physi- cists. We may have to deal, as I have already suggested, with an actual breaking up of the ether-vortexes, which, according to Lord Kelvin’s theory, compose the material par- ticles, or we may be confronted with a dissolution of matter into some un- known primary form, the Akasa of the old Vedas. Experiments show that this matter is reiiected, some- times very well, sometimes poorly; but in all cases the various metals behave in a curious manner, which I havestndied, and the results obtained, though probably not free of error, because of the great ditliculties in getting an exact estimate in such an investigation,were, nevertheless, sulf- ciently positive as to lead me to the conviction that the same medium or element which is concerned in the setting up of the electro motive ten- sion between metals in contact is present in the streams of Roentgen. It might have been proper to say, in the spirit of more modern views on contact electricity, that these streams are formed by ether, but I have pre- ferred to use the term “primary matter;” for, although the expression “ether” conveys a perfectly definite idea to the scientific mind, there exists, nevertheless, much vagueness as to the structure of this medium. The matter projected is not revealed by spectral analysis, and itdoes not seem to produce any appreciable mechanical nor even heating eiiecls, nor is it deflected by a magnet, all of which facts tend to show that it can not be composed of molecules of any known substance. The streams exercise a powerful action upon a photographic plate or fluorescent screen, but I look upon these results as obvious con- sequences of the energetic impact. Of the various more or less plausible views in regard to the formation of these streams outside of the vessel, the simplest, to my mind, is to assume an actual projection through the walls of the bulb of the disintegrated cathodic matter. Granted that there are par- ticles sudticiently small within the bulb, then all velocities, up to many thousands of kilometers per second, are not only possible, butalso probable; and, even if the particles would not be further disintegrated by the impact against the wall or other comparatively opaque body within the bulb, they surely would penetrate through great thicknesses of mostsubstances. My ex- periments in this direction have shown that all the disintegration is practi- cally accomplished in the Erst impact against the more or less impenetrable obstacle within the bulb, the second impact having seemingly little effect, as might be inferred from well estab- lished mechanical principles. I have also found that the place of first and most energetic impact, be it the anode, cathode or wall'of the vessel is invariably the principal source of the rays or streams. Again, quite in accordance with mechanical princi- ples, the penetrative power of the streams is the greater the more com- plete the disintegration. Thus, for instance, rays which have traversed thick opaque objects, and are pre- sumably further disintegrated, pass more freely through dense substances. An observation to this effect has likewise been made by Professor Wright, who was the first to publish dednite results in the United States. I End that bulbs with thick walls give rays of greater penetrating power. It should be, of course, understood that I do not mean by this a greater outward edect. It is principally the above fact which makes it appear more probable that the matter projected is not a homo- j/ETWOHS stream. but consists of par- ticles of varied magnitude moving J with diderent velocities, for, were the former the case, the penetrative power would depend chiefly on the velocity. In the practical use of the Itoentgen streams it would, therefore, seem very important to find a method of filter- ing and rendering them homogene- ous, for only by such a method can we hope to obtain exact results in their investigation. Streams of per- fectly uniform velocity and character, if produced, would no doubt be more suitable for the purposes of research. Since the disintegration of the elec- trodes, especially if they are of aluminum, is so slow that no appre- ciable diminution of the weight results even after long use; it follows that the ,matter conveyed by the Roeutgen streams is so minute as to escape detection. Some bulbs, which I have used for a number of months, showed that the bombarded spot of the glass was entirely permeated with particles of the aluminum electrode, but it would probably require years of constant use to accumulate any appreciable amount of matter outside. Referring to a tube \vith an electrode of aluminum, it is a noteworthy fact that, if properly managed, it does not impair in quality, but, on the contrary, seems to improve; whereas, when a platinum electrode is used, the life of the bulb is very short, owing to the conductor being deposited on the walls, which deposit, as I have ex- plained on another occasion, renders didicult the passage of the discharge. Namely, as soon as some of the pro- jected particles strike the conducting layer, they _impart a similar electri- fication to the latter, and a repulsion is exerted upon the particles follow- ing. The result is an apparent in- crease in the resistance of the tube. The above defect of the platinum electrode, despite of its eiectiveness, must, in my opinion, lead to its abandonment. It has been suggested that the Roentgen rays may bedue simply toa propagation of electro-static stress; but, on this assumption, it is difficult to conceive how rays could be pro- duced in instances when the glass wall is at a high temperature and consequently conducting, or when the impact plate or inclosure is of metal and connected to the ground. Stokes has recently considered the possi- bility that the impact of the cathodic stream on one side of a partition might give rise to a molecular motion on the other side without necessarily there being a transit through the partition. According to this view, which I have likewise considered some time ago, it would appear that the material streams might start on the outer side of the wall of the tube, in which case only the air would be responsible for the effects, _and the futility of a spectral analy is test would be in a certain measure ac- counted for. But is it not more probable to assume an actual passage and shattering of matter, as allevi- dences point in this direction ? As- suming that, as Professor Stokes now thinks it probable, the disturbance is non-periodic and still capable of pro- ducing effects characteristic of trans- verse vibrations of extremely high frequency, it seems to me a serious question Whether the old Newtonian views on light should not be recon- sidered rather than the conclusion drawn that the novel manifestations observed by Roentgen are due to transverse vibrations, when there is no experimental evidence to this effect, nor even a satisfactory expla- nation found how the cathodic impact 277 might give rise to waves of a higher frequency than those of light. Being, as I am, Ermly convinced of the existence of material streams, I look upon the unsuccess of the at- tempts of demonstrating an actual transit of matter as being due to either the rninuteness of the amount or else to the state of the matter, but rather to the former cause, as all peculiarities of the streams point in this direction. In my opinion, no experimenter need be deterred from carrying on an investigation of the Roeutgen rays for fear of poisonous or generally deleterious action, for it seems reasonable to conclude that it would take centuries to accumulate enough of such matter as to interfere seriously with the process of' life of a person. But I look confidently to the demonstration of actions of a purely qualitative nature. Forin- stance, de pite of the danger of such an_ assertion by encouragement which might be given to quacks, I would say that I expect with the utmost confidence the demonstration of a germicidal action. In addition to the physiological effects, to which I have early drawn attention, I have more recently observed with powerful tubes that a sensation of pain is pro- duced in the forehead above the eyes just as soon as the current is turned on. This sensation is very similar to that one frequently experiences when stepping from a dark room into the glare of bright sunlight, or when walking for some time over Holds of fresh~fallen snow. As to the hurtful actions on the skin, which have been variously reported, I note that they are misin- terpreted. These eiects have been known to me for some time, but I have been unable, on account of press- ing matters, to dwell on the subject. They are not due to the Iioenigen rays, but merely to the ozone gener- ated in contact with the skin. Ni- trous aoid may also be responsible, to a small extent. The ozone, when abundantly produced, attacks the skin and many organic substances most energetically, the action being no doubt heightened by the heat and moisture of the skin. After exposing the hand, for instance, for some time, the skin loses its elasticity, which causes a tension and pain, and sub- sequently an iuliammation and blister- ing. This occurs mostly only at short range, but may be produced by a single terminal bulb, or generally~by a very highly exhausted bulb, in which the terminals act independently, at reater distance. Owing to this, I have always taken the precaution, when getting impressions with the rays, to guard the person by a screen made of aluminum wires which is connected to the ground. preferably through a condenser. The radical means, however, of preventing such actions is to make impossible the access of the air to the skin while exposing, as, for instance, by immers- ing in oil. As this would be incon- venient in most cases, a metallic screen should be resorted to. The action of the ozone on some substances, when placed near the bulb in such a way 'that the gas is generated on their sur- faces, is so powerful that the sub- stances are practically destroyed in a few minutes. When a wire heavily insulated with rubber is connected to the terminal of a high-frequency coil, sometimes an exposure of barely a minute is sufticient to completely wreck the rubber insulation. There are certain commercial insulating compounds which are even more quickly destroyed, but which I will not enumerate. because of a possible disadvantage to thc manufacturers. Gutta-percha, beeswax and paraiiine stand the attack very Well, and such (Continued on page X.)

2. TESLA ON ROENTGEN STREAMS. fcimtfmwa from page sm wires should be used with high-fre- quency coils. This powerful action ot the ozone was observed by me first about tivo years ago, when performing an experiment which was shown to many persousin my laboratory. The experiment consisted of charging a person, standing on an insulated stand, svithapotential approximating one and one-half million volts, which was alternated several hundred thou- sand times a second. Under such conditions luminous streams break out on all parts of the body, especially abundantly on the feet, hands, hair, nose and ears. I subjected myself a number of times to this experiment, which seemed to oiier no otherdanger except the possible rupture of a blood vessel, if the skin was very dry and non-conducting. I then noted ou myself and others after effects resem- bling much those attributed to the Roentgeu rays. With currents pro- duced by perfected electrical oscilla- tors, such as were described in one of your recent issues, [See ELECTRICAL Review, September 30, 1896.-En] the production of the ozone is so abundant that it' is sufficient to merely turn on the current for a few seconds and ozonize strongly the atmosphere of a large hall. These currents are also capable of bringing about chemical com- binations, of which the chief is that of the nitrogen \vith the oxygen of the atmosphere, and an immense possibility, which |I have been following up for a long time, is opened up; namely, the com- bination of the nitrogen of the atmos- phere on an industrial scale by practically no other means than mechanical power. It merely fer- tilizers of the soil would be manu- factured in this manner, the benefits to humanity derived therefrom would be incalculable. From the above- named action of the ozone, it follows that the experimenter should use the indicated precaution, for, while ozone in small quantities is a most bene- ficial disinfectant, when generated in large quantities it is not free of danger. It is an unpleasant duty to say on this occasion a few words on the sub- ject of “making the blind see” by means of the Roentgen rays. This sensational topic has been' given a wide circulation in the journals. Is it not cruel to raise such hopes when there is so little ground for it ? For, irst of all, the rays are not demon- strated to be transverse vibrations. If they were, we would have to ind means for refracting them to make possible the projection of a sudicieutly small image upon the retina. As it is, only a shadow of a very small object can be projected. What pos- sible good oan result from the appli- cation of these rays to such purposes? The shape ot the small object might eventually be recognized by impress- ing the retina, but the sense of touch is more than sulilicient to convey such impressions. Luminous sensationsare well known to he excited in two ways; namely, by mechanical shock and electrical transmission. Both of these, I think, are present in the Roentgen streams, and hence such an effect on the optic nerve might be expected. I may say, however, that I can not conhrm some of the experi- ments reported. For instance, when a hand is put before the closed eyes it is easy to distinguish the shadow, much the same as before the light of a candle; but when the tube is inclosed, and all light from the same excluded, I fail to get such an impression. The latter is, therefore, chieiiy due to ordi- nary light, or else my tubes act differ- ently from those experimented with by others. It may be proper to recall ELECTRICAL REVIEW vel. 2o_N0. 23 here that in ordinary bright sunlight, especially in the southern climates, it is easy to distinguish the shadow of objects, and even their rough out- lines, with the eyes shut. Proceeding on the assumption that we have in reality to deal with mate- rial streams, it is important to inquire which are the best conditions to be maintained when taking impressions with the sensitive screen or plate. First, the experimenter will easily observe that there are two causes which, with a given hulo and coil, tend to increase the intensity of the impressions. One of these may be said to lie in the bulb, the other in the coil. The latter, being most generally made of many turns of fine wire, is very sensitive to changesin the capacity of bodies attached toits ter~ minals. The capacity of these bodies, therefore, in such a coil largely de- termines the diiference of poten- tial. At a certain degree of ex- haustion this capacity assumes such a value that the pressure rises toa maximum, this tending to give the highest velocity to the cathodic stream, and, consequently, to give rise to the most intense rays. But at that degree of exhaustion it may happen, and usually does happen, that the cathodic streams are not most abundant. To produce the best result it is necessary that both of these causes should be made to co- operate by a careful proportionihg of the dimensions of the bulb, which, in practice, is very dilicult, inasmuch as the experimenter has to avail him- self of commercial bulbs which may or may not be best suitable for his coil. This simple consideration shows the great advantage of the use of a coil which contains no fine wire and is capable of giviuga heavy current through the secondary far in excess of what even thelargest bulb requires. Assuming the physician has learned how to manipulate his apparatus to best advantage, he will next notice that, to secure the clearest detinition, he will have to maintain a certain pressure on the terminals of the tube, dependent chieliy on the distance and degree of opacity of the object in- vestigated. It goes without saying that the definition is the better the smaller the spot from which the rays are emanating, but this is true only when impressions are taken at very small distances. When the distances are large, it is a disadvantage to use a too small radiating surface, as then the density is diminished to such a degree that the action is too weak. Discarding this consideration, it is clear that, if the rays are intense, the more opaque portions of the body are likewise penetrated and much detail is lost, whereas, when the rays are less intense, the impression might be altogether too week to bring out sumcient detail. _ _ To illustrate in a popular manner the best way to proceed, I shall avail myself of a simple illustration. Sup- pose that there would be imbedded between two panels of cloth a foreign object, such as acoin, and it is desired to locate it. We may accomplish this by'placing behind the, cloth a card- board, for instance, and then firing from a certain distance a load of fine shot through the cloth in the region where the coin is supposed to be located. The shot will penetrate the cloth on all points except on the place where the coin is located, and on the cardboard behind, this place will be plainly indicated by the absence of the marks. Exactly in this way we proceed in applying the Rocntgen rays to the location of such a body. Roentgen gave ns a gun to fire-a wonderful gun, indeed, projecting missiles of a thousaudfold greater peuetrative power than that ofa can- non ball, and carrying them probably to dist.ances_of many miles, with velocities not producible in any other way we know of. These missiles are so small that we may tire them through our tissues for days, weeks, months and years, apparently, without any hurtful consequence. Instead of the cardboard to indicate the path of the missiles, he gave us what( is properly called a Roentgen screen, which be- comes luminous on all places where it is hit by the missiles. Where the latter are prevented from hitting the screen by the intervention ot the opaque body, the screen does not glow and we observe the shadow ot the object. It is simple enough to pro- ject the shadow of an object in this way, but when it is required to show the finer detail of the structure of the object, the difficulty begins. It will at once appear that, to produce such a result to best advantage, two conditions will have to be more or less realized. Firstly, the screen should be composed ot such material that it is capable of becoming lumi- nous by the faintest impact; and, secondly, the missiles should all be of uniform size, and should move with uniform velocity. Neither of these two conditions has so far been realized in practice, for all the bodies we know require a violent impact to become luminous, and no way has been found as yet to produce a uni- formity in velocity and magnitude ot the supposed projectiles. But a little thought leads immediately to the conclusion that there will be a cer- tain velocity of the missiles which will give, under all conditions, the best dednition. This velocity is easily ascertained by trial. Evidently the definition will be best when the bullets which pass through the densest parts of the body strike the screen so feebly as to not make it light up, whereas, those passing through portions of slightly smaller density hit it sudiciently strong as to make it light up feebly. The more sensitive the screen to impact, that is, the weaker an impact is re- quired to make the screen light up, the more detail will be revealed. It therefore follows that, in the appli- cation ot the Roentgen rays, not the body which fluoresces strongest, but the one which is most sensitive, is best suited for finer work. The above considerations have led me to adopt the following procedure, which, in practice, has proved very successful. The Roentgen screen is first applied to the body to be investi- gated, the pressure at the terminals of the tnbe being very much reduced. The pressure is then slowly and grad- ually raised. It will be presently ob- served that, at a certain pressure, the shadow of the object examined is clearest. But as the vacuum is in- creasing, the pressure generally rises, and the image gets blurred in spite of the screen getting much brighter. Just as soon as the clearness is slightly diminished, the experimenter should for a few moments reverse the cur- rent, lowering alittle the vacuum in this manner. The current being again given the dirrction it had at first, namely, that which causes a slow and steady increase of the \'aCUll¥11, the shadow gets again clear, and by such easy manipulation the best result may be secured. An addi- tional advantage, however, is gained, because the frequent reversals produce a brighter phosphorescence of tl1e screen. When taking a photograph, the hulb should be watched through the screen and the switches manipu- lated in the above manner. To give a practical example of the elfectiveness of this procedure, Ineed only mention one of the instances which have come to my notice, A few months ago I investigated the case of Mr. Cornelius Mack; of Watertown, Mass. Mr. Mack, while performing his duties many years ago, was struck by a bullet which lodged somewhere in the chestnnd could not be located. I applied the screen vainly a number of times; for although the streams penetrated the body with such ease as to make the screen behind appear bluish white, and reveal all the bones of the body, I could not observe the missile. I then resorted to the above indicated means, and immediately and easily the exact location ofthe projectile, between the shoulder blade and one of the ribs, was ascertained and the bullet success- fully extracted. NIKOLA TESLA. New York, November 30.