1895] 



MICROSCOPICAL JOURNAL. 



389 



this circumstance — the large number of the instruments and of 

 of those who use them — in a very striking manner discloses the 

 weak points in the construction of the stands, certain parts of 

 which, with great regularity, become defective after some U'^age. 

 These weak parts include the micrometer screw, which has be- 

 come unreliable and shaky; the prism which has undergone tor- 

 sion and flexure in a sufficient degree to produce lateral motion, 

 making focussing problematic; and the fastening of the prism to 

 the stage which has lost its firmness. The author attributes 



these shortcomings mostly to the fact that the continental 

 stand, unlike the Jackson pattern, in none of its parts offers to 

 the hand a solid and convenient hold by which it may safely be 

 transferred and manipulated. 



As a corrective, a reversed arrangement of the component 

 parts of the fine adjustment is recommended. The prism sleeve 

 is solidly united with the stage and the prism with the tube car- 

 rier. When the fingers of the operator now grasp the instru- 



