of the double refraction in strained glass. 

 Table VI. O 41. 



329 



Remarks on 41. 



A. April 17 (morning). B. April 17 (afternoon). 



Both taken with a narrow central diaphragm and both corre- 

 spond to first extinction. 



Fig. 5. Glass O 41. 

 G = 1-745 + -0156 ( X iq 4 00 ) -'0236 



/ X-5400 \- 

 V 1000 ) 



4Voo 5000 sfoo 



Wave-lengths in tenth-metres. 

 VOL. XII. PT. V. 



tO0O £5"oo 



+ Observations B. 



7000 



A.j 



Table VI. 



22 



