The Microscope in Section with the Images : i, 2, 3, Beams of light to the mirror ; C 

 Image distance, i. e.; from eye-point, E-P, to virtual image (O4); CD Condenser diaphragm; 

 EP Eye-point of ocular; F] Upper focal plane of the objective; F2 I^ower focal plane of the 

 eye-piece ; I, Mechanical tube-length, /.. e,: from top of draw-tube to screw for insertion of 

 objective; 61 Object on the stage ; 62 Image formed by the objective were no field lens 

 present ; O3 > Image when field lens is present ; O4 Virtual image ; A Optical tube-length, 

 i. e.: distance from the upper focal plane of the objective (Fi ) to lower focal plane" of eye- 

 piece F2. 



