A Geometric Slide PJwtomicrogmjjJnc Apparatus. 



support is simply on a plane 

 surface. It is clear that any 

 apparatus supported in this 

 manner has no freedom to 

 move, and if it is taken off 

 its base for any purpose, 

 will, on being replaced, go 

 back with absolute accuracy 

 to its original position. 



It may be that in a 

 description of this sort the 

 arrangement sounds a little 

 complicated, but, as I have 

 already mentioned, the accu- 

 racy of the component parts 

 need not be of a high order ; 

 but the design is such that, 

 even apart from such accu- 

 racy, the arrangement is 

 absolutely positive in its 

 results. 



In the photomicrogra- 

 pliic apparatus here shown 

 (fig. 2), we have endea- 

 voured to embody the prin- 

 ciple of the geometric slide 

 throughout, and, apart from 

 that, the design of the ap- 

 paratus is such that extreme 

 rigidity is obtained. There 

 is little or no liability of 

 alteration of any of the parts 

 of the apparatus as tlie re- 

 sult of climatic change of any 

 description, and, owing to its 

 rigidity, the whole appara- 

 tus would move together if 

 subjected to any shake or 

 vibration. 



The base consists essen- 

 tially of castings made from 

 two patterns, a pair of each 

 casting being used. These 

 are designed on girder prin- 

 ciple, and each part of the 

 supporting castings may be 

 resolved into a triangle, so 





B 2 



