7U 



SUililARY OF CURRENT RESEARCHES RELATING TO 



tliickiiess, with both faces truly parallel. Cut the circle which is to 

 form the stage as large as the instrument will permit, and in accord- 

 ance with the following dii-ections. 



Cut the well-hole l-16th inch larger than the well-hole of the 

 stage ; make a collar, or short tube, out of the same material used for 

 the stage : turn the outside to proper dimensions, so as to fit the well- 

 hole of the new stage, the upper edges of both being " flush," and 

 solder in position. 



Next turn accurately the under and projecting part of the short 

 collar, or tube, so that it will exactly fit the well-hole of the main 

 stage ; place it thereon, and cut ofi' any portion of the collar that may 

 project beneath the stage. 



In the stage thus far towards completion, if the collar projects 

 1-1 6th inch, this will be found ample for its support. 



All that remains to be done is to fit the new stage with plain 

 spring-clij^s, which can be dune in a few moments out of a piece of 

 watch-spring ; or, if there is room enough, an object-carrier can be 

 provided on Zentmayer's principle. As to rotation in the optic axis, 

 the author says that if it did so rotate with one objective, it would be 

 pretty sure to fail with another. The compensation must be supplied 

 by finger manipulations easily acquired and as easily practised. " A 

 grand good tiling about this improvised stage is, that it can be placed 

 in position or removed therefi'om in a moment "s time." 



Bausch and Lomb Optical Co.'s Compressors. — The first of these 

 (fig. 138) is simply a modification of the Optical Co.'s Trichinoscope,* 



made, however, shorter 

 and broader. Besides its 

 use as a compressor, it 

 forms with the addition 

 of the lens a convenient 

 pocket Microscope for 

 field use in collecting In- 

 fusoria, Algfe, etc. 



The other form (fig. 

 139) is a parallel com- 

 pressor. Parallelism is 

 obtained by attaching a 

 spring and two pins on 

 the under side of the arm 

 carrying the upper plate. 

 The pins slide in two 

 sockets and when the 

 milled head is screwed 

 down the upper plate is 

 pressed on the lower, the 

 pins descending into the 

 sockets. On releasing the screw, the spring forces back the arm. 

 In order that the upper plate may be turned on one side as shown by 



Fig. 133. 



Fig. 139. 



See this Journal, ii. (1SS2) p. 258. 



