8^ Microscopical Essays. 



are- both moveable, fo that their refpe&ive diftances may be eafily 

 varied. There is alfo a condenfmg glafs to the ftage, for in- 

 creating the denfity of the light, when it is re hefted by the mirror 

 from a candle or lamp. It is furnifhed with two mirrors, one 

 plane, and the other concave, and may be ufed as a hngle 

 microfcope. 



A B, Fig. i , Plate IV. reprefents the body of the microfcope, 

 containing a double eye glafs, and a body glafs ; it is here (hewn 

 as fcrewed to the arm C D, from whence it may be occafionally 

 removed, either for the convenience of packing, or when the 

 inftrument is to be ufed as a fingle microfcope* 



The eye glafles and the body glafles are contained in a tube 

 which fits into the exterior tube AB ; by pulling out a little this 

 tube, when the microfcope is in ufe, the magnifying power of each 

 lens is increafed., 



The body A B of the microfcope is fupported by the arm CD, 

 this arm is fixed to the main pillar C F, which is fcrewed firmly to 

 the mahogany pedeftal G H ; there is a drawer to this pedeftal, 

 which holds the apparatus. 



N I S is the plate or ftage which carries the Aider-holder K L» 

 this ftage is moved up or down the pillar C F, by turning the 

 milled nut M ; this nut is fixed to a pinion, that works in a 

 toothed rack cut on one fide of the pillar. By means of this, 

 pinion, the ftage may be gradually raifed or depreffed, and the 

 object adjufted to the focus of the different lenfes. 



