[Annals X. V. A. S., XL, X<>. 3, pp 39. to 43, March 30, 1898.] 



THE USE OF THE FLUOROSCOPIC SCREEN IN 

 CONNECTION WITH RONTGEN RAYS. 



C. C. Trowbridge. 



(Read November 2, 1896.) 



In a previous paper b\' the writer entitled " An ' X-ray De- 

 tector ' for Research Purposes," containing a description of an 

 instrument designed and constructed for use in the study of 

 Rontgen rays, a reference was made to those investigators who 

 had improved the methods of using the fluorescent screen in 

 connection with the Rontgen rays. Mention was made of Pro- 

 fessor E. Salvioni, of Perugia University, Italy, and Professor 

 William F. Magie, of Princeton College, as being two investi- 

 gators who, working independently, were the first to construct 

 and describe an instrument which greatly simplified the manner 

 of using the fluorescent screen in experiments with these rays. 



Professor Salvioni gave an account of his apparatus in a paper 

 which he read before a meeting of the Perugia Medico-Chirug- 

 ical Society on February 5, 1896. A translation of the same 

 appeared in Nature, March 5, 1896, page 425 (No. 1375, 

 Vol. 53). The original manuscript having been published in 

 the Proceedings of the Academia Medico-chirugica di Perugia 01 

 February 6, 1896, Vol. VIII, No. 1-2. The instrument was 

 called a " cryptoscope," and was described in the article as a 

 cardboard tube 8 centimeters high, having at one end a screen 

 of black paper, on which had been spread a layer of calcium 

 sulphide, a substance that is fluorescent under the influence of 

 X-rays. At the other end, where the eye was placed, a lens 

 was fixed, which gave an image oi the screen. 



The priority of publication in this country of a description of 

 a piece of apparatus similar to that described above, belongs to 

 Professor ]\Iagie, who wrote a letter concerning it to TJie Med- 



(39) 



