694 



RONTGEN RAYS. 



various substances, concluded that potassium plat- 

 inocyanide was the best. 



The first attempt to make the shadow picture visi- 

 ble by using a screen covered with fluorescent mate- 

 rial without impressing it permanently upon a sensi- 

 tive plate was that of Prof. Salvioni, of Perugia, Italy, 

 who was followed by others, notably by Edison in 

 the United States, who calls his device the fluoro- 

 scope. All the devices replace the photographic 

 plate by a screen covered with one of the fluorescent 

 substances mentioned above, and provided on the op- 

 posite side from the source of X rays with an arrange- 

 ment for keeping side light from the observer's eye. 

 When used on a large scale, however, the screen 

 has been placed in a darkened room so that this 

 lastmay be dispensed with and the shadow picture 

 may be viewed by a large number of persons at 

 once. Arrangements of the kind were tried also 

 independently about the same time as by Salvioni 

 by Prof. A. W. Wright, of Yale, Mr. E. P. Thomp- 

 son, of New York, and Prof. Magie, of Prince- 

 ton. By experiment substances were found that 

 respond so quickly to the radiation that shadow 

 pictures of moving objects can be seen, and the 

 effect is practically that of an actual shadow cast 

 by light that has the property of penetrating opaque 

 bodies, though in reality, of course, the light is 

 generated at the surface of the screen, which is a 

 source, not a reflector, of the visible radiation. In- 

 stead of causing the rays to impress the sensitive 

 plate directly, a combination of fluoroscope and 

 camera has also been used, probably first by Dr. I. 

 Mount Bleyer, of Naples, Italy (" Electrical Engi- 

 neering," July 1). In such an arrangement the 

 photograph is taken not by X rays, but by ordinary 

 light generated at the fluoroscope. 



The shadow pictures, whether permanent or tem- 

 porary, have been used for a great variety of pur- 

 poses. They have largely served merely to gratify 

 curiosity, as by enabling coins to be seen within a 

 purse, etc., but they have also been put to a practi- 

 cal use, especially in the domain of surgery, in which 

 malformation of bones has been made visible and 

 foreign objects located in the flesh or viscera. To 

 mention a few examples: As early as March 28 

 a needle was located and removed from a girl's 

 finger in Nottingham, England, when other means 

 of location had failed, and on April 4 Drs. Ren- 

 ton and Somerville, in London, discovered- with 

 the rays an unsuspected case of unreduced disloca- 

 tion of the phalanx. On March 21 bullets were 

 clearly located in the hands of two men by Prof. D. 

 C. Miller, of Cleveland, Ohio, who has also examined 

 many hands that had been injured in accidents, and 

 determined in each case the exact nature of the in- 

 juries. Dr. W. I. Morton, of New York, has dem- 

 onstrated the use of the rays in dental surgery, 

 showing with them " errant fangs," making teeth 

 visible before their eruption, revealing exostosis, 

 necrosis, or tuberculosis, and showing clearly the 

 extent, area, and location of metallic fillings. The 

 rays have also been used to guide the operator in 

 removing foreign bodies from the throat, the posi- 

 tion of the body and of the forceps used to ex- 

 tract it being clearly visible, and the operator 

 hence enabled to grasp the body at once. The rays 

 also detect calcareous infiltrations in the arte- 

 ries, etc. 



In demonstrative anatomy the position of the 

 bones is shown, and with the fluoroscope their 

 movements as well as the successive stages of ossi- 

 fication in a growing infant. 



Elihu Thomson (" Electrical World," Oct. 10) has 

 given considerable attention to taking stereoscopic 

 radiographs of the human bones, and is of opin- 

 ion that this method will prove of great value in 

 allowing the parts to be seen in their proper rela- 



tions. When viewed by means of a stereoscope, 

 the bones in such a picture stand out in high relief, 

 while appearing semitransparent. 



Among other actual or proposed applications of the 

 rays are the detection of false from true gems (Fig. 

 11) and of adulterations generally, and their use for 

 illuminating purposes, the rays causing an extended 

 surface covered with a fluorescent salt to give light. 

 Experiments have also been made with a view to 

 discovering whether the rays can be perceived by 

 the human eye, and it has been satisfactorily shown 

 that they do stimulate the retina in some cases, in- 

 cluding a few where the subject was unable to see 

 objects by ordinary light, owing to cataract or some 

 similar obstruction. These experiments were re- 

 garded by some as showing that blind persons might 

 some day be made to see by means of the rays, but 

 so far there have been no grounds for such an ex- 

 poctation. The rays have also been utilized in 

 France for the study of fossils, which, it has been 

 found, they assist by giving clear indications of in- 

 terior structure, thus enabling the palaeontologisMo 

 tell at once, for instance, whether a given bone is 

 that of a bird, a reptile, or a mammal, and affording 

 him an opportunity of studying the cerebral cavity 

 of an intact skull. 



It has been suggested also that the rays be used 

 to examine the contents of a suspicious package 

 which it is feared may contain an infernal machine, 

 and experiments with packages made up for the 

 purpose indicate that a machine of this kind may 

 be very easily detected. 



Nomenclature. A very large number of names 

 have been proposed for the rays, for the various 

 phenomena connected with them, and for the me- 

 chanical devices for producing and recording them. 

 Of these none are yet used exclusively, although 

 many have found no favor at all. The rays them- 

 selves are known indifferently as X rays or Rontgen 

 rays. If there is any distinction in use, the former 

 may be described as the popular, the latter as the 

 scientific name. The permanent pictures produced 

 by the rays on a sensitive plate have been most fre- 

 quently called sciagraphs or skiagraphs (Greek a-idti, 

 shadow), radiographs, and sometimes shadowgraphs, 

 and the fluorescent screen with its attachments for 

 direct observation has been called the fluoroscope, 

 the sciascope or skiascope, and the radioscope. All 

 of these names have been objected to, save perhaps 

 that of Rontgen rays. The use of the element skia 

 might refer to any shadow picture, that of radio 

 implies that the rays are typical of all radiation, 

 whereas they are only a special and almost abnor- 

 mal case, and fluoroscope is more properly applied 

 to a device for detecting fluorescence. 



Theory of the Rays. Thus far the theories of 

 Rontgen rays have been of two types : first, that 

 which regards them as an undulatory phenomenon 

 of the ether, and, second, that which looks on them 

 as streams of particles or fluid. Of the first type 

 there are two divisions, one of which supposes the 

 rays to be simply ultra-violet light of wave length 

 far shorter than any that has been observed hither- 

 to, and that which supposes them to differ from 

 ordinary light in the direction of their vibration, 

 which, instead of being transverse to the ray, is lon- 

 gitudinal, as in the case of sound. 



This last-named theory was from the first very 

 attractive to physicists. Unless the lurniniferous 

 ether were differently constituted from any known 

 elastic body, a vibratory disturbance in it should 

 consist in part of longitudinal vibrations, and yet 

 no evidence of such vibrations had ever been ob- 

 tained. The theory that the rays were simply light 

 of very small wave length appealed to those who laid 

 special stress on the likenesses between the Rontgen 

 rays and ultra-violet light. The emanation the- 



