316 THE ACTION OF GLASS AND QUARTZ. [MEMOIR XXII. 



MEMOIR XXII. 



ON THE ACTION OF GLASS AND QUARTZ ON THE RADI- 

 ATIONS THAT PRODUCE PHOSPHORESCENCE. 



From the Philosophical Magazine, Aug., 1844. 



CONTENTS : Phosphorescence by rays from a Leyden spark through 

 quartz. From the voltaic arc. It is occasioned by the more refran- 

 gible rays. Imperviousness of glass. Professor Henry's experiments. 

 Comparison of the chemical and phosphorogenic rays. 



AT the distance of six inches from the terminations of 

 two blunt wires, between which the spark from a Ley- 

 den-jar was caused to pass, I placed a lens of quartz, the 

 focus of which for parallel rays was six inches, and then 

 intercepted the resulting beam by a diaphragm, with a 

 circular aperture in it one third of an inch in diameter. 

 I had caused an equiangular prism of quartz to be cut 

 and polished from a large and faultless crystal; it was 

 cut transverse to the axis. This prism I placed in such 

 a way that, in dispersing the beam coining through the 

 circular aperture, I got rid of double refraction and ob- 

 tained only one spectrum ; this was received on a metal 

 plate, which, having been washed over with gum-water 

 and sulphide of lime dusted on it, offered a uniform 

 phosphorescent surface which might be set in a vertical 

 plane. When the spark passed, I saw that the plate 

 was phosphorescing on those portions where the more 

 refrangible rays had fallen. 



But the transient light of a Leyden spark did not last 

 long enough, nor was the phosphorescence it produced 

 powerful enough to enable me to conduct the experiment 



