CHAP. III.] 



THE MICROSCOPE. 



247 



an instrument employed to throw magnified images on a screen 

 at a distance, in order to render them visible to a large number 

 of spectators at the same time. This is the solar microscope, 

 described in the Forces of Nature, and which is thus called because 

 the light with which the object is illuminated is the light from the 

 sun's rays. When the sun does not shine it would be necessary 

 to relinquish this powerful means of demonstration in laboratories 



FIG. 188. Photo-electric microscope. 



if we did not possess a source of nearly as bright a light as the sun. 

 We refer to the electric light. Therefore, we have the photo-electric 

 microscope, represented in Fig. 188. 



There is an important application in microscopy, which must not 

 be passed over in silence. This is the photography of the objects 

 thus observed in all their exact and curious details, by which means 

 permanent and exact records may be secured, 



