1054 



BECORD OF CURRENT RESEARCHES RELATING TO 



mounting is so contrived that by movement of the lever-arm (shown 

 with shaped handle attached), the diaphragms can be successively 

 moved over the achromatic condenser, the optical part of which is 

 shown by dotted lines. The stage is suitably hollowed out beneath 

 to facilitate the adjustment. 



Fig. 124 shows an improved form, which Messrs. Swift regard as 

 superseding that shown in Fig. 123. The diaphragms are here cut in 



Fig. 124. 



a metal " calotte " mounted eccentrically, so that by rotation the 

 apertures pass successively over the top of the achromatic condenser ; 

 the rotation is effected by the projecting edge of the calotte — somewhat 

 as with the diaphragms in Gillett's condenser. 



It should be observed that Mr. Zeiss has for some time applied 

 calotte diaphragms to his " Travelling Microscope " ; * but they do not 



Fig. 125. 



act quite in the plane of the stage, nor are they constructed to be 

 used in conjunction with the achromatic condenser. It is evident, 

 however, that the effect obtained is similar to Mr. Bulloch's applica- 

 tion of the Gillett diaphragm above the condenser.f In Messrs. Swift's 



See tliis Journal, ii. (1879) p. 9.5.5. 



t Post, p. 1078. 



