26 THE MICROSCOPE, ETC. 



within another) the rack being attached to a bar 

 placed some distance from the tube carrying the eye- 

 piece and objectives. When attached to the tube 

 itself it is impossible to adopt any arrangement for 

 shortening the tube, the consequence of this is that 

 the surface of the ground glass in the camera, 

 covered by the image, is greatly contracted owing to 

 the length of tube between the objective and mouth 

 of the bellows. 



Nothing belonging to the microscope is susceptible 

 of more improvement than the fine adjustment, and 

 anything which would supersede the present very 

 inferior methods by which this is affected, would be 

 welcomed by microscopists. This adjustment should 

 be separated from the eye-piece tube far enough to 

 allow of the attachments necessary for working it 

 from a distance. It should respond immediately to 

 the slightest rotation in either direction, and the 

 object should suffer no apparent shake or displace- 

 ment, when moving in or out of focus. 



The eye-piece tube must be removable from the 

 body, or better from another tube about an inch long 

 attached to the arm carrying the objectives. The 

 way this is accomplished is of no importance as long 

 as it is possible. 



The stage should be firm, and as thin as is 

 compatible with the use of the sub-stage apparatus, 

 to be described. Circular in form and possessing 

 some arrangement by which movements in a rec- 

 tangular, circular or horizontal direction may be 

 smoothly and easily communicated to the object, by 



