278 S. C. AKEHURST ON A CHANGER FOR SUB-STAGE CONDENSERS. 



metal plates, the flat sides of which are set 1| inch apart, form 

 a groove for the slide to work in. These plates are screwed to a 

 metal collar, the diameter of which is such as to allow the slide- 

 condenser changer to be fitted to any microscope that has a sub- 

 stage made to the R.M.S. gauge. Fig. 1 shows a plan of the 

 slide changer in position, while fig. 2 gives a sectional elevation 

 along the line A B, fig. 1. When three, or more, condensers are 

 used it is desirable to have each mounted on a separate slide ; 

 but when only two condensers are used, one slide may be 

 sufficient, as the optical parts can be made interchangeable. 



Fig. 2. 



When the slide with condenser has been pushed home, a screw, 

 working through one of the plates, holds this firmly in position. 



This changer does away with the necessity of a throw-out 

 sub- stage, and any variation of centrality in the condenser can 

 be adjusted by the centring screws in the regular way. 



To rack down the sub-stage fitting, withdraw and insert a new 

 slide, are all the movements that are required to obtain a change 

 of condenser, and this can be effected as readily as a change of 

 objective on a revolving nose-piece. 



Journ. Quekett Microscopical Club, Ser. 2, Vol. XII., No. 74, April 1914. 



