« 
Histological Preparations by Sunlight. 259 
“age to pass the solar pencil through a piece of ground glass. 
s plan is recommended in all the treatises on photo-micro- 
graphy, and has hitherto been employed in the solar work done 
at the Army Medical Museum. The method is effectual in 
the sereen, and is sadly deficient in contrast. These faults are 
reproduced in photographs of objects thus illuminated, and, 
Moreover, the time of exposure is enormously increased. Such 
ie 3 pe ai 1 d sa from 
may be greatly diminis 8 ‘. fs f a second, and that 
mirror outside the shutter and thence into the dark room, A a 
iginal paper on photo-micrograp y- 
* This Journ., II, vol. xlii, p. 189, Sept., 1866. 
