POWELL AND LEALAND'S STAND. 91 



stage is firm and strong, and at the same time so 

 thin, that the utmost obliquity of illumination is 

 attainable, the under portion being entirely turned 

 out ; it has a dove-tailed sliding bar movable by rack 

 and pinion ; into this bar slides the sub-stage, having 

 vertical and horizontal motions for centring, and also 

 a circular motion ; the sub- stage carries the various 



FIG. 47. Powell and LealancVs Microscope, with Amid prism arranged for 

 oblique illumination. 



appliances for underneath illumination, removed in the 

 woodcut. The achromatic condenser is seen detached. 

 Powell and Lealand have another pattern, larger 

 and more massive in its general arrangements. The 

 construction of the stage and sub-stage differ some- 

 what ; both resting on a large solid brass ring, firmly 

 attached to the stem of the instrument. The upper 

 side of this ring bears a sort of carriage that supports 



