ZOOLOGY AND BOTANY, MICROSCOPY, ETC, 663 



tube about f inch long and ^ inch diameter, and into this the objectives 

 (which are of correspondingly small size) slide direct. It is said that 

 " by this plan the following important advantages are obtained : the 

 object-glasses are more quickly and easily changed ; the rack may be 

 more uniformly worn by sliding them in at different distances ; and 

 should any portion of the rack be broken or deranged at the focussing 

 points, the object-glass may still be used by sliding it in or out as 

 may be required." 



Smith's Object Plate and Finder. — The following note was read 

 by Mr. James Smith at the May meeting of the Society : — " In the 

 October number (1880) of the Journal of the Society, pp. 880-1, a 

 very simple form of stage is described by Messrs. Schmidt and 

 Haensch. It appeared to me that the use of a graduated arc for a 

 finder was so effective that it might be easily and usefully applied 

 to some English Microscopes; and in the following description and 

 accompanying drawings, I have endeavoured to carry out the idea. 



The only piece of apparatus required, where there is a good stage- 

 plate (moving vertically) to which it can be applied, is a thin piece of 

 metal somewhat of the shape A moving on a centre E by means of a 

 small screw on the stage-plate ; the bottom of the piece is cut into an 

 arc of a circle, of which E is the centre, and upon this arc are 

 graduated the divisions. Attached to this plate is an object-holder 

 B. The only extra thickness interposed between the object and the 

 source of illumination is that of the graduated plate (about ^\ of an 

 inch). In the case of my own Microscope, where the stage-plate is 

 not convenient for the purpose, the finder-plate is screwed to another 

 thin plate C, as in the drawing, which slides vertically on the con- 

 centric stages. At the foot of this plate C is engraved or painted a 

 small double pointer D, to read off the position of the graduated arc, 



