microscope is reflected by the thin film of glass into 

 the eye and the image is apparently projected beyond 

 the glass upon the paper where the pencil point may 

 trace out its details. 



The best form and that which has nearly superceded 

 all others which have made pretense to giving good 

 results is the Abbe camera lucida, Fig. 56. 



While in the original construction it gave superior 

 results it has been gradually improved, so that in its 



Fig. 56. 



complete state it leaves nothing to be desired. Its 

 price is necessarily high but it is also offered in simpli- 

 fied form to meet more modest demands and will with 

 proper use do very good work although not as good 

 nor with equal facility as the more complete. 



The optical construction, Fig. 57, is the same in all 

 forms. Two 1-4 inch rectangular prisms of which one 

 has a silvered diagonal surface with a central opening of 

 one half the diameter of the pupil of the eye, are cemented 



1 68 



