Microscopes of Powell, Ross, and Smith. By E. M. Nelson. 551 



merit must be regarded as an answer to the Ross Microscope, figured 

 in the Penny Cyclopedia of 1839, which necessarily must have been 

 made before the publication of that work. The flat folding tripod 

 foot is replaced by a solid one, and rigidity is given to the body in a 

 different way from that of Eoss's model. There is a triangular bracing 

 at the top of the limb, and a guide is placed lower down, upon which 

 the body slides ; the stage is evidently a modified form of Eoss's, and 

 there is a Wollaston condenser with rackwork focusing, the conical 



Fig. 146. 



end reminding one of the cone diaphragms of earlier non-achromatic 

 models. The fitting of this condenser to a separate arm on the limb 

 shows a distinct improvement over all preceding models; both Powell 

 and Eoss attached theirs to the underneath part of the main stage, 

 while in this there isan elementary kind of substage. The nose-piece 

 fine adjustment of this Microscone possesses all the errors inseparable 

 from those of its class. It has been stated that this Microscope was 



