Microscopical Essays, \ 30> 



Fig. 5 reprefents the exterior tube of the telefcope, which is 

 to be unfcrewed from thereft, as it does not make any part of 

 the microfcope; the cover k, which protects the objeft-glafs, 

 ferves alfo as a box to contain the Aiders with the obje&s, and a. 

 fmall mirror. 



Fig. 4 is a view of this cover when taken off: unfcrew the top. 

 part of it, and the mirror, Fig. 6, may be taken out ; unfcrew the 

 cover of the lpwer part, and you will find therein the two circu- 

 lar Aiders reprefented at Fig. l and 2, 



Fig. 3 reprefents the three internal tubes of the telefcope,., 

 which conftitute the microfcopic part thereof. Draw the tubes 

 out in the manner that is feen in Fig. 3 ; then on the infide, but 

 at the lower end of the exterior tube, you will find a fhort tube,, 

 which ferves as a ftage to hold the objecT: and fupport the mir- 

 ror ; pull this tube partly -out, and turn it, fo that a circular hole 

 which is pierced in it may coincide with a fimilar hole in the ex- 

 terior tube. This tube is reprefented as drawn out at Fig. 3, the 

 mirror, Fig. 4,. placed therein at L M, and the tranfparent Aider 

 fixed at N O. 



Fig. i reprefents the Aider with tranfparent objecis. 



Fig. 2, that with opake. They are made of ivory, and turn 

 on a pin at the center 5 the flit end of this pin fits on the edge of 

 the tube, which is then to be puflied up, fo that the lower end of 

 the exterior tube may bear lightly on the upper fide of the Aider,, 

 agreeable to the view which is given at. Fig. 3. Now pu(h down 

 the fecond tube till the milled part falls on the milled edge of the' 

 $ exterior 



