BOSS'S MICROSCOPE. 



79 



of construction, in those parts especially which are most 

 liable to tremor, and to the due balancing of the weight 

 of the different parts upon the horizontal axis. The 

 " coarse " adjustment is made by the large milled-head 



Fig. 39. Ross's No. la Large Microscope, with Binocular arrangement and 



Object-glass. Scale &. 

 B. Sub-stage of ditto, with new Achromatic Condenser. Scale $. 



situated just behind the summit of the uprights, which 

 turns a pinion working into a rack cut on the back of a 

 very strong flattened stem, that carries the transverse arm 

 at its summit. A second milled-head (which is here con- 



