F. E. Wright — New Petrographic Microscope. 409 



Figs, la, 2, 3. 



Fig. la. Section through microscope of fig. 1, showing working parte. 

 The letters T, A, B, C, H, W, Q, F, 0, IT, Y, E, L, and G, refer to the same 

 parts as in fig. 1. I = lower iris diaphragm ; N, upper nicol ; X, Y, Z, brass 

 parts effecting revolution of upper nicol ; P, revolving stage supporting 

 movable plate, O. 



Fig. 2. Section showing stage P and microscope plate supporting stage 

 and other revolving parts and support for revolving nicol device, C ; T, cross 

 section of bar connecting two nicols ; this bar slides accurately in the arms 

 A and B of fig. la. 



Fig. 3. Cross section through mechanical plate 1 of stage. Ii, I 2 , brass 

 plates screwed to revolving stage P and with wedge-shape sides in which 

 rectangular plate K can move in an east- west direction, the movement being 

 effected by the screw H 2 . J 1} J 2 and J 3 , three plates attached to under side 

 of stage plate, 0, and forming grooves for plate K, permitting stage plate to 

 move only in north-south direction, the movement being accomplished by 

 screw, H,, which in turn fits in a sliding block attached to the upper plate 

 O. and traveling in the pin, D. 



construction are shown in 

 and cross bar at B the 

 released and the lower nicol 



% 



la. 



By 

 rod 



withdrawn 



means 

 T can 

 or revo 



of the screw 



be instantly 



lved by itself 



