1052 



SUMMARY OF CURRENT RESEARCHES RELATING TO 



Wenham's Frictionless Fine -Adjustment. — Messrs. Eoss havo 

 applied to Mr. F. H. Wenham's Radial Microscope the form of fine- 

 adjustment shown in fig. 220. 

 Fig. 220. A V-slide is fitted within the body-tube, 



carrying at its lower end the nose-piece N, and 

 is pressed downwards by a spiral spring S. It 

 is moved against the spring by the revolution of 

 two " snail " cams C C, between the edges of 

 which revolves a steel roller R forming the axis 

 of, and actuated by a large milled head H, 

 passing longitudinally through the slide of the 

 coarse adjustment and projecting slightly on 

 either side, in a convenient position for work. 



By this system an extremely sensitive 

 focusing is obtained, though a difficulty has to 

 -■ be overcome in the tendency of the roller to 



slip between the cams. 



Swift's Cam Mechanical Stage. — Mr. J. 

 Swift, in 1884, utilized the cam for a mechanical 

 stage in the manner shown in fig. 221. There 



