122 



Microscopical Essays. 



G, a final 1 brafs box to hold the filver fpeculum H. 



H, a fmall filver concave fpeculum, defigned td reflecl the 

 light from the mirror on opake objects ; it fhould only be ufed 

 with the fhallow magnifiers. It is applied in different ways to 

 the compound microfcope ; fometimes to a tube fimilar to 

 that reprefented at X, which Hides on the lower part of the 

 body ; fometimes it is fcrewed into the ring of the piece O; the 

 pin of this generally fits into one of the holes in the llage. When 

 this fpeculum is ufed, the Aider- holder mould be removed. 



I, a fifh-pan, whereon a fmall fifh may be fattened, in order to 

 view the circulation of the blood ; it's tail is to be fpread acrofs 

 the oblong hole at the fmalleft end, and tied faft by -means of the 

 ribbon-fixed thereto, by moving the knob which is on the back of 

 it through the flit made in the ftage ; the tail of the fifh may be 

 brought under the lens which is in ufe. 



K, a cylindrical piece, intended for the folar opake microfcope ; 

 by pulling back the fpiral fpring, fmaller or larger objecls may be 

 confined iu it. 



L, a long Reel wire, with a fmall pair of pliers at one end,, 

 and a flee! point at the other ; the wire flips backwards or for- 

 wards in a fpring tube, which is affixed to a joint, at the bottom 

 of which is a pin to fit one of the holes in the ftage ; this piece is 

 ufed to confine fmall objecls. 



1, a fmall ivory cylinder that fits on the pointed end of the 

 fteel wire L; it is defigned to receive opake objecls. Light- 

 coloured 



