THE SIMPLE MICEOSCOPE. 



59 



pillar, about six inches long, screwed into a tripod base ; .to 

 the upper part of the pillar is attached, by screws with milled 



Fig. 37. 



heads, a large flat stage, provided with a spring clip, and 

 other apparatus for holding the objects. By means of the 

 large milled head, a triangular bar, having a rack, is raised 

 out of the pillar; this bar carries a lens-holder, having a 

 horizontal movement in one direction, effected by a rack and 

 pinion, and a circular one, by turning on a pin. It is also 

 provided with a concave mirror, for reflecting the light 

 through the hole in the stage; a condensing lens, for the 

 purpose of illuminating opaque objects, and a pair of forceps 

 for holding small objects, may be applied to either of the 

 holes in the stage. This microscope is usually supplied with 

 lenses of one inch and one half inch in focal length for 

 dissecting; but the higher powers generally employed are 

 either doublets or triplets; or it may be converted into a 



