MICROSCOPE, ETC. 25 



CHAPTER III. 



The Microscope, Illumination, Etc. 



Before beginning a detailed description of the 

 microscope, a few hints to the uninitiated are neces- 

 sary. Avoid purchasing instruments adorned with 

 innumerable screws and mechanical arrangements 

 for performing the various movements. 



AH superfluous apparatus, is not only useless, but 

 a decided hindrance to accurate investigation, in 

 fact the various additions generally made to the first 

 class instruments of the present day, are an insult to 

 the skilled microscopist and a means of perpetuating 

 clumsy manipulations. On the other hand many 

 excellent instruments are made, which, owing to some 

 peculiarity of shape, are useless for photography. 



The first essential of a microscope is a firm heavy 

 stand, so arranged that the body may be inclined at 

 any angle between horizontal and perpendicular and 

 clamped in that position. It should be high enough 

 to allow space beneath the stage for sub-stage appar- 

 atus, and the points on which it rests should be 

 sufficiently distant from each other to prevent the 

 instrument being easily overturned. 



The coarse adjustment is best accomplished by 

 rack and pinion movement, (not by one tube sliding 

 within another) the rack being attached to a bar 

 placed some distance from the tube carrying the 



