CHAPTER VIII. 



MICBOSCOPICAL FRAGMENTS.* 



( 1 .) On Stopping False Light in Microscopes andEngiscopes. 

 — This is one of the most important requisites in an instru- 

 ment ; for however perfect it may be, if there is the least 

 light reflected from the mountings of the glasses, or 

 within the tubes, the fog and glare produced will ma- 

 terially deteriorate their performance ; it is therefore 

 absolutely necessary that all their surfaces be made as 

 sombre as possible. The usual method of effecting this 

 is to cover the parts while hot with a black lacker, made 

 by mixing lamp-black in a solution of shell-lac in strong 

 spirits of wine. A more elegant method, and better 

 suited for delicate work, is to wash the surface, previously 

 freed from grease and tarnish, with a solution of platina 

 in nitro-muriatic acid (chloride of platina) ; -after remain- 

 ing on the work a few minutes it is wiped off, the surface 

 having assumed a deep brown or black colom*. If these 

 are not at hand, a strong solution of muriate of ammonia 



■* Extracted from Mr. Pritchard's Microscopic Cabinet, 



