94 



Microscopical Essays. 



By the nut Q it may be moved from eaft to well; ; it may be 

 elevated or deprefled by the nut R. 



d e, two fcrews to faften the microfcope to a window-mutter. 



The box for opake objects is reprefented at H I K L ; it con- 

 tains a plane mirror M, for reflecting the light that it receives 

 from the large lens to the object, and thereby illuminating it ; S 

 is a fcrew to adjuft this mirror, or place it at a proper angle for 

 reflecting the light. 



V X two tubes of brafs, one Aiding within the other, the exte- 

 rior one in the box HIKL; thele carry the magnifying lenfes : 

 the interior tube is fometimes taken out, and the exterior one is 

 then ufed by itfelf. Part of this tube may be feen in the plate 

 within the box HIKL. 



At H there is a brafs plate, the back part of which is fixed to 

 the hollow tube h, in which there is a fpiral wire, which keeps 

 the plate always bearing againft the fide H of the brafs box H I 

 KL. The Aiders, with the opake objects, pafs between this 

 plate and the fide of the box ; to put them there, the plate is to 

 be drawn back by means of the nut g. 



i kt a door to one fide of the opake box. 



The foregoing pieces confiitute the feveral parts neceflary for 

 viewing opake objects. I mail now proceed to defcribe the Angle 

 microfcope, which is ufed for tranfparent objects : but in order 

 to examine thefe, the box HIKL rauft be firft removed, and in 



its 



