57 



NOTES OF OBSERVATION ON THE RONTGEN RAYS 



BY HENRY A. ROWLAND, N. R. CARMICIIAEL, AND L. J. BRIGGS 



[American Journal of Science [4], /, 247, 248, 1896 ; Philosophical Magazine |5], XLI, 



381, 382, 1896] 



The discovery of Hertz some years since that the cathode rays pene- 

 trated some opaque bodies like aluminium, has opened up a wonderful 

 field of research, which has now culminated in the discovery by Rontgen 

 of still other rays having even more remarkable properties. We have 

 confirmed, in many respects, the researches of the latter on these rays, 

 and have, repeated his experiment in photographing through wood, 

 aluminium, cardboard, hard rubber, and even the larger part of a milli- 

 meter of sheet copper. 



Some of these photographs have been indistinct, indicating a source 

 of these rays of considerable extent, while others have been so sharp 

 and clear cut that the shadow of a coin at the distance of 2 cm. from 

 the photographic plate has no penumbra whatever, but appears perfectly 

 sharp even with a low power miscroscope. 



So far as yet observed the rays proceed in straight lines and all efforts 

 to deflect them by a strong magnet either within or without the tube 

 have failed. Likewise prisms of wood and vulcanite have no action 

 whatever so far as seen, and, contrary to Rontgen, no trace of reflection 

 from a steel mirror at a large angle of incidence could be observed. In 

 this latter experiment the mirror was on the side of the photographic 

 plate next to the source of the rays, and not behind it, as in Rontgen's 

 method. 



We have, in the short time we have been at work, principally devoted 

 ourselves to finding the source of the rays. For this purpose one of 

 our tubes made for showing that electricity will not pass through a 

 vacuum was found to give remarkable results. This tube had the 

 aluminium poles within 1 mm. of each other and had such a perfect 

 vacuum that sparks generally preferred 10 cm. in air to passage through 

 the tube. By using potential enough, however, the discharge from an 

 ordinary Ruhmkorff coil could be forced through. The resistance being 



