0. N. Rood — Reflection of the Rontgen Rays. 175 



nary light, that the shadows of the vertical wires on the 

 right hand are doubled ; the corresponding lines of the X-ray 

 picture are blurred and indistinct ; again, in the picture taken 

 by ordinary light the liorizontal lines are distinct, which is also 

 the case with the X-ray picture ; in fact when the original nega- 

 tives were examined, there was found to be a marked corre- 

 spondence between the two, which " pointed," as I remarked 

 in my article in Science, " strongly to the conclusion that in 

 the act of reflection from a metallic surface the E-ontgen rays 

 behave like ordinary light." This negative contained evidence 

 that some diffused X-rays had also reached the sensitive plate, 

 for the image on it was as a general thing not as sharp as if it 

 had been produced entirely by regularly reflected rays. Also 

 an image of two vertical wires was produced outside of the 

 space that could be reached by regularly reflected X-rays. This 

 negative was too weak to furnish prints showing all the details, 

 but from a study of it the conclusion was reached that a sur- 

 face of platinum foil reflected the X-rays in the same general 

 manner in which it reflected ordinary light, but that the per- 

 centage of the scattered X-rays was considerably larger than in 

 the case of ordinary light, or in other words, that the platinum 

 surface acted in connection with the X-rays as though it were 

 imperfectly polished, a result that had been predicted by Dr. 

 W. Gibbs. 



Photographic experiments were also made to ascertain what 

 percentage of the X-rays underwent reflection. Plates from 

 the same box, protected in the same way, were placed at the 

 same distance from the discharge tube, without the interven- 

 tion of a mirror, and the time of exposure was diminished, till 

 with similar development a similar image was obtained. The 

 result of this determination was, that platinum foil at an angle 

 of 45° reflected -g^th part of the incident X-rays. 



Experiments loith tnirrors of speculum m.etal and platinum. 



In order still further to study this matter and to extend the 

 investigation to a second reflecting substance, on May 9th I 

 employed a mirror made of speculum metal, its dimensions 

 being 64°'°' by 120°'°'. This mirror was flat, but not partic- 

 ularly well polished. The shell tube was again used, and 

 matters were so arranged that only one-half of the sensitive 

 plate could be reached by regularly reflected ordinary light, or 

 by regularly reflected X-rays. A coarser netting was em- 

 ployed, the distance from wire to wire being 6*46°'°'; the 

 diameter of the wire was 0-8°'°'. The same draw-slide wag 

 used to protect the plate ; near its top it was covered by alu- 

 minium foil with a thickness of 0*023°'°' ; at the bottom it was 

 crossed by a strip of aluminium plate having a thickness of 



