!'LAT3 LIV. 



Fig. 331. 



Pressure frame, used in photographic j : 





i .' ed for condensing tb 



a lamp, as Kiriu^ed by Hr. SUadbolt. p ,3. 



Fig. 



of pressure frame, p. -_'T'J. 



Fig. 



lor obtaining parallel rays, as recommended by Gerlach. p. 2SO. 



Fig. 



Pressure frame. 



Fig. a35. 



JST 



Sectiocal views of 

 e-holders. 



To illustrate the obaei-rations m 



the position of the condensing lens, p .i 



[To face pai- 



