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SUMMARY OF CURRENT RESEARCHES RELATING TO 
two main parts, and its aperture is of the horseshoe form, which affords 
convenient space for the finger to lift the slide, so as readily to bring the 
oil in contact when an immersion lens is used. This stage is provided, at 
desire, either with clip springs or a sliding dovetail clip with rectangular 
divisions. 
Fig. 77. 
The fine adjustment is of the most solid construction, and yet is 
extremely sensitive, and is so made that it is entirely covered at all 
points, thus preventing the possibility of injury by dust. The micro- 
meter screw works directly in the centre of f its fitting, and its milled 
head reads to 1/500 in. The draw-tube is*' graduated to millimetres. 
