82 THE MICROSCOPE. 



The general plan of Powell and Lealand's Compound 

 Microscope is represented in fig. 40. The tripod-stand 

 gives a firm support to the trunnions that carry the tube 

 to which the stage is attached, and from which a triangular 

 stem is raised by the rack-and-pinion movement set in 



Fig. 40. Powell and Lm.iand's Mirrnscope, with Amid prism arranged 

 for oblique illumination. 



action by the double-milled head, whereby the coarse ad- 

 justment of the focus is obtained. To the upper part of 

 the triangular bar a broad arm is fixed, bearing the com- 

 pound body ; this arm is hollow, and contains the mechanism 

 for the fine adjustment, which is effected by turning the 

 email milled-head. The arm is connected with the tri- 

 angular bar by a strong conical pin, on which it turns, so 

 that the compound body may be moved aside from the 

 stage when necessary ; by a mechanical arrangement it 



