Microscopical Essays, 



The two upper plates each contain a magnifying lens, but of 

 different powers : one of thefe confines and keeps in their places 

 the fine point F, the forceps G, and the fmall knife H. 



To ufe this inftrument, unfcrew the upper lens, and take out 

 the point, the knife, and the forceps ; then fcrew the lens on 

 again, place the objecl: on the ftage, and then move it up or 

 down till you have gained a diftinft view of the objecl, as one 

 lens is made of a fhorter focus than the other ; and fpare lenfes, 

 of a ftill deeper focus, may be had if required. This little micro- 

 fcope is the invention of Dr. Withering, and is defcribed by him 

 in his " Botanical Arrangements." It's principal merit is it's 

 Simplicity. 



Common Botanical Microscope. 



This little inftrument is reprefented at Fig. 2, Plate VI. It 

 appears to me preferable to Dr. Withering's, being equally 

 fimple, more extenfive in it's application, and the ftage un- 

 incumbered ; though that of M. Lyonet feems better adapted 

 than either to the purpofes of difle&ion. 



A B, a fmall arm, carrying the two magnifiers, one fixed to 

 the upper part as at B, the other to the lower part of the arm at 

 C ; thefe may be ufed feparately or combined together. The 

 arm A B is fupported by the fquare pillar I K, the lower end of 

 which fits into the focket E of the foot FG; the ftage DL is 

 made to Aide up and down the fquare pillar ; H, a concave mir- 

 ror for reflecting light on the objecl:. 



To 



