POLARIZED LIGHT. 



109- 



35 25". This tube may be made of cardboard, as 

 shown, in Fig. 30 (also the exact dimensions). The 



Fig, 29. 



width from a to I, and c to d = 12mm., that from 

 b to c, and d to e, equal to the length of the thin 

 gliLss, when placed at the proper angle. It will be 

 found convenient to cut the cardboard partially 



9 



Firj. 30. 



through with a sharp knife from 6 to/, c to g, and 

 d to h ; near the bottom of the first division on 

 the other side paste a strip of card i ; carefully 

 paste the two edges of the card together; drop 



