60 HOW TO SEE WITH THE MICROSCOPE. 



together around the same centre, which is the thickness 

 of an average slide over the stage. 



The entire sub-stage with its milled heads can be 

 taken off, so that there shall be nothing in the way 

 when using direct light. The mirror is arranged so 

 that it can be used in any direction, backward, forward, 

 over or under the stage. The mirror and also the sub- 

 stage have graduated circles, so that the obliquity can 

 be noted. 



The movement of the body is effected by rack and 

 pinion connected with two milled hea^s, which connect 

 with the lever of the slow motion, thus preserving the 

 distance between the objective and the eye-piece. The 

 slide on the body tube is long and broad, thus prevent- 

 ing vibration or lateral motion when using the milled 

 heads or the micrometer screw ; the latter is grooved 

 so that it can be used for photographic purposes. 



The instrument is mounted on tripod base, with re- 

 volving platform. The platform is graduated, and upon 

 it two standards are fixed, between which the instru- 

 ment turns to the angle when so used, or turning hori- 

 zontally for drawing, or for measuring angular aperture. 

 The centre on which the instrument turns, when placed 

 horizontally, is in a direct line with the object on the 

 stage. 



The binocular model is arranged with rack and pinion 

 for different width of eyes ; the prism is so fixed that 

 the distance remains the same. The society screw at 

 the end of the body is arranged as a safety nose-piece, 

 with spring, so that the danger of breaking slides is 



