smith's inverted microscope. 



709 



the first one was constructed by N'ach.et, of Paris. Its design is 

 to enable the chemist to carry on observations under the micro- 

 scope without the risk of injuring his objectives, or at least having 

 his view obscured, by the fumes arising "from liquids experi- 

 mented upon. This has always been a serious difficulty in 



Fig. 430. 



micro-chemical research, and, together with the difficulty of 

 manipulating in the limited space between the object-glass and 

 the stage, has hitherto prevented this branch of scientific inquiry 

 from being fully illustrated. " The only way," says Dr. Smith, 

 " by which these difficulties can be surmounted, is by putting 

 the object-glass beneath the stage and the object above it, with 

 an optical arrangement of such a nature as to permit observa- 

 tion." It vp-as with this view that M. Chevalier made a chemical 



