of the double refraction in strained glass. 



:32:j 



A. 



Table III. O 154. 

 B. 



0. 



Remarks on 154. 



A. July 2. (Diaphragm central.) Band observed for first 

 extinction. Band very hazy and diffuse, even in the yelloiu. 



B. July 4. Diaphragm found afterwards to be not quite 

 central. Band observed for second extinction. Band was far 

 more difficult to observe than for the first extinction and was 

 quite invisible when no diaphragm was interposed, even when in 

 the ordinary test between crossed Nicols the glass showed a uni- 

 form tint. 



C. July 6. Experiments of July 4 repeated with the dia- 

 phragm more accurately central. 



[The observations for this glass were troublesome and its 

 behaviour appeared peculiar.] 



