Microscopical Essays, u* 



' ' ' id 



The glafs tubes are belt cleaned with a piece of wafh leather. 



If a fountain-lamp is left partly filled with oil, it may be liable 

 to overflow ; this happens by the contraction of the air when 

 cold, and it's expanfion by the warmth of a room, the rays of 

 the fun, or the heat of the lamp when re-lighted : this accident 

 may be effectually prevented by keeping the refervoir filled, the 

 oil not being fubje£t to expanfion like air. On this account, thofe 

 with a common refervoir are beft adapted for microfcopic pur- 

 pofes. 



to - examine opake objects with the lucernal 



Microscope. 



The microfcope is reprefented as mounted, and entirely ready 

 for this purpofe, in Fig. 1, Plate III. 



To render the. ufe of this inflrument eafy, it is ufually packed 

 with as many of the parts together as poffible ; it occupies on 

 this account rather more room, but is much lefs embarraffing to 

 the obferver, who has only three parts to put on after it is taken 

 out of its box, namely, the guide for the eye, the ftage, and the 

 tube with it's magnifier. 



But to be more particular, take out the wooden Aide A, then 

 lift out the cover and the grey glafs from their refpeclive grooves 

 under the Aide A. 



Put the end N of the guide for the eye L M N into it's place, fo 

 that it may ftand in the pofition which is reprefented in this figure. 



K Place 



