April 30, 1896] 



NA TURE 



RECENT WORK WITH RONTGEN RA YS. 



TN our last week's number, Prof. J. J. Thomson brought 

 together and discussed observations of prime importance 

 -elected from the mass of material recently published on Rontgen 

 lys. As a supplement to this, and in continuation of the 

 , ineral summaries which have already appeared in Nature, we 

 present the following notes on papers and communications 

 received during the past few days. 



Prof. Oliver Lodge has sent us the following announcement, 

 dated April 20. 



" It has been asserted that the action of X-rays on a film is a 

 photographic one, depending on the fluorescence of the glass 

 backing. The truth is that a film on a ferrotype plate is just 

 about as rapid as a similar film on glass. Thick films are much 

 better than thin. It may be further interesting to state that if 

 the platinum disk on which the kathode rays inside the bulb are 

 converged is connected to the kathode, it fails to act as a source ; 

 if it be insulated, it acts fairly ; while if it is connected to the 

 anode, it constitutes a vigorous source." 



It will be remembered that Prof. Rontgen found that "films 

 can receive the impression as well as ordinary dry plates" 

 (Nature, January 23, p. 274), but he was doubtful whether the 

 photographic effect was secondary or not. 



From a number of papers dealing with various properties 

 of Rontgen's rays, we learn that Herren V. Novak and 

 O. Sulc (Prague) have observed the relative opacity for 

 X-rays of different substances, both simple and compound 

 {Zeitschrift fiir Physikalische Chemie, xix. 3). They conclude 

 That the absorbing powers of the chemical element depend 

 n their atomic weight alone, and that the absorbing power 

 I a compound depends only on the atomic weights of the 

 elements of which it consists, and not on the complexity of its 

 molecules. It seems probable that the average atomic weight of 

 a compound affords an index of its absorbing power. In 

 the Jenaische Zeitschrift fiir Nattirwissenschaft, Dr. A. Winkel- 

 mann and Dr. R. Straubel (Jena) have investigated the refrac- 

 tion of Rontgen rays, and by using prisms of various metals, 

 obtain in each case a value of about i : 0*0038 referred to air. 

 They also have measured the reflection produced by a sheet of 

 tinfoil, and the relative transparency of different kinds of glass 

 to Rontgen radiations. All glasses made with lead are found to 

 be comparatively opaque. The same writers have experimented 

 on the action of fluor-spar in intensifying the actinic effects of 

 X-rays, and have found that the best results are obtainable with 

 a coarse powder of the fluor-spar ; finer powders producing a 

 ics? marked effect. This effect is due to fluorescence, the spar 

 emitting radiations whose index of refraction is about i '48 ; 

 indicating a wave-length of 219x10"*. The March number 

 of the Atti delta Reale Accademia dei Lincei contains two 

 papers, one by Signor Augusto Righi, and the other a joint 

 paper by Drs. A. Fontana and A. Umani (Rome), both 

 >f which deal with the effect of Rontgen rays in stopping 

 iie action of Crookes' radiometer. The effect is found to be 

 , urely electrostatical, and to be due to the electrification of the 

 i;lass bulb containing the radiometer ; when the bulb is wetted, 

 or electrification prevented by the interposition of a conducting 

 screen, the radiation from a Crookes' tube does not affect the 

 ! adiometer in any way whatever. 



Mr. A. W. Isenthal has sent us the following letter, a propos 

 if Winkelmann and Straubel's paper. He says : — " It may be 

 of interest to your readers to learn that, within the last few 

 weeks, Prof. Dr. Winkelmann and Dr. Straubel, of Jena 

 I'niversity, have been successful in reducing the exposure re- 

 luired for the production of radiograms to a few seconds only. 

 Acting on the few directions given, I have made a few prelim- 

 inary trials, the result of which is very promising. By simply 

 backing the sensitive plate with a most inexpensive material, I 

 have obtained fair negatives of the finger-bones in about ten 

 seconds, using only a 3-inch spark. As the rays in this method 

 liave first to pass through the glass of the sensitive plate, there 

 is a probability of still further reducing the necessary exposure 

 l>y substituting .sensitive films (on celluloid) for the ordinary 

 jihotographic plate." 



With reference to the use of fluorescent screens in reducing 

 he time of exposure, we have received the following letter from 

 I )r. M. Van Heurck, of the Botanical Gardens, Antwerp, 

 hrough Dr. Wynne t). Baxter :— 



"I notice in your issue of April 16, that Messrs. L. 

 : ;leekrode and J. William Giffcrd announce that they have been 

 ble to reduce the time of exposure in radiography by the use of 



NO. 1383. VOL. 53] 



a fluorescent screen. Mr. Basilewski communicated the same 

 fact to the Paris Acad^mie des Sciences on March 23 last. 

 Allow me, however, to lay claim to priority in this application 

 of fluorescent screens, as the same was announced by me in 

 various Antwerp journals on March 8, and again on the 12th of 

 that month, in the Annates (Beiges) de Pharmacie, an extract 

 from which, in pamphlet form, I send herewith. You will also 

 find described therein a chemical substance, viz. a newly-dis- 

 covered double fluoride of uranyl and ammonium, with which 

 screens can be made, at a nominal cost, of a luminosity and of a 

 clearness superior to that of any screen now known to exist." 



The combination of a fluorescent .screen with a photographic 

 plate was one to which every worker with Rontgen rays 

 would naturally be led. Prof. M. L. Pupin gave a description 

 of the combination before the New York Academy of Sciences 

 on March 2. At a meeting of the Academy on April 6, reported 

 in Science of April 10, he described an arrangement of apparatus 

 by means of which it was found possible to produce very strong 

 photographic effects, " but not sufficiently strong for penetration 

 through the thigh and the trunk of the human body at rea.son- 

 ably short exposures and at long enough distances from the tube 

 to obtain the desirable clearness in the pictures of these massive 

 parts. A completely successful application of Rontgen's beauti- 

 ful discovery to surgery depends for the present on a successful 

 solution of the problem just mentioned. I have obtained one 

 satisfactory solution with the method which I first described 

 before the Academy on March 2. It consists in placing in con- 

 tact with the photographic plate a fluorescent screen, and thus 

 transforming most of the Rontgen radiance into visible light 

 before it reaches the sensitive film. Photographs of the hand 

 were thus obtained at a distance of twenty-five feet from the tube 

 with an exposure of half an hour. At the distance of four inches 

 the hand can be photographed by an exposure of a few seconds. 

 It was in this manner only that I succeeded in photographing on 

 a single plate the whole chest, shoulders, and neck of my 

 assistant, with an exposure of seventy minutes and at a distance 

 of three feet between the plate and the tube. The collar-button 

 and the buttons and clasps of the trousers and the vest show very 

 strongly through the ribs and the spinal column. This result 

 seems to prove beyond all reasonable doubt the applicability of 

 radiography to a much larger field in surgery than was expected 

 a few weeks ago." 



A communication on the same branch of the subject has been 

 received from Mr. A. A. C. Swinton, under date April 22. We 

 print his letter in full. 



" The chemical action of the Rontgen rays upon a photo- 

 graphic film may be either a direct action or may be a secondary 

 effect, due to the fluorescence produced in the support, or in 

 the gelatine and silver bromide of the film itself. Be this as it 

 may, the fact that an ordinary photographic film supported on 

 celluloid is almost completely transparent to the rays, as may 

 easily be proved with a cryptoscope, and also the fact that it is 

 possible to simultaneously impress many super-imposed films, 

 show that only a very small fraction of the energy in the rays is 

 utilised under ordinary circumstances. 



" As long ago as January 30, in some remarks that I made at 

 the close of Mr. Porter's demonstration at University College, 

 I suggested as a means of more completely utilising the energy 

 in the rays, and thereby shortening the necessary exposure, the 

 use of suitable fluorescent material applied either in the form of 

 a screen behind the photographic film, or introduced into the 

 substance of the film itself. 



" Since I first made this suggestion, I have tried numerous 

 experiments in the direction indicated. These were at first un- 

 successful owing to the screens used not having been properly 

 prepared. Some weeks ago, however, on renewing the experi- 

 ments with a screen thickly coated with potassium platino- 

 cyanide and gum, placed behind a celluloid photographic film, I 

 obtained conclusive evidence that by this means the necessary 

 exposure could be greatly shortened, and that in a less degree 

 the same result could be accomplished by the employment of a 

 screen thickly covered with powdered fluor-spar. 



" The chief objection to this method lies in the fact that it is 

 very difticult to avoid granular results. Unless the fluorescent 

 material be in a very fairly divided condition, its grain shows 

 distinctly and mars the detail of the finished picture. The 

 platinojcyanide does not work so efficiently when finely powdered 

 as when in moderately coarse crystals, but good results can be 

 obtained by thickly coating a thin celluloid film with an emulsion 

 of this salt ground to fine powder in collodion, and using the 

 screen so prepared with its celluloid surface ip contact with the 



