CONSTRUCTION OP THE MICROSCOPE. 



37 



in two directions, at right angles to one another; and thus 

 different parts of objects can be brought successively into 



Fig. 24. — Valentine's Microscope. 



the field of view. The arm n p, for carrying the lenses, 

 is attached to the triangular bar d by a conical pin, on 

 which it is made to turn horizontally, and the arm itself 

 can be lengthened or shortened by means of the rack and 

 pinion m o ; hence the lens q can be applied to every part 

 of an object without moving the stage. 



The mirror / is fitted into the largest of the three legs, 

 and consists of a concave and plane glass reflector. To 

 the under side of the stage is fitted a Wollaston's condenser 

 k ; and the lens is made to slide up and down by means 

 of two small handles projecting from the cell in which the 

 lens is set. Two small tubes i, with either a condensing 

 lens for opaque objects, or a pair of forceps, may be 

 attached to this side of the stage. The magnifiers are 



