180 0. N. Rood — Reflection of the Rontgen Rays, 



amount of regularly reflected X-rays, along with a certain 

 quantity of X-rays that are not equally scattered in all direc- 

 tions, but that stray from their more orderly companions only 

 to a moderate extent; that is, the diffusion has the char- 

 acter that obtains with ordinary light reflected from imper- 

 fectly polished mirrors. It would appear then, according to 

 these experiments, that metallic surfaces which are highly pol- 

 ished for ordinary light are only imperfectly polished for the 

 X-rays, and it may be added that all the experiments detailed 

 in this paper are in harmony with the idea that the X-rays 

 consist of transverse waves like those that constitute ordinary 

 light, differing from them only in being much shorter. 



In the earlier experiments I was much annoyed by the pres- 

 ence on the plates of systems of variously curved lines, which 

 either obscured or blotted out the photographic impression. 

 These curves had a breadth of a few millimeters and were 

 never twice alike in shape. They always made their appearance 

 in the preliminary experiments on reflection, and sometimes 

 even when the X-rays were allowed to fall directly on the 

 plate-holder without the intervention of a mirror. They 

 appeared to be due to ordinary static induction, and were 

 finally abolished by replacing the sheet-iron slide that contained 

 the plate by one made of wood, and insulating the plate-holder 

 by supporting plates of glass. The large lead screen between 

 the discharge tube and the plate-holder was also carefully 

 grounded. With these precautions the electrical markings 

 became very faint, and indeed quite imperceptible except with 

 short exposures that furnished very faint negatives. 



New York, June 17, 1896 



