FIG. 1. Diagram to show the parts of the compound microscope. (After Russell 



and Hastings) 



O\, object; 2 , real image in F 2 , transposed by the collective lens to 3 , real image 

 in eyepiece diaphragm ; O 4 , virtual image formed at the projection distance C, 250 

 mm. from eyepoint EP; CD, condenser diaphragm; L, mechanical tube length 

 (160 mm.) ; 1, 2, 3, three pencils of parallel light coming from different points of the 

 source of illumination. (After Bausch & Lomb Optical Co.) 



