106 PKACTICAL TREATISE ON THE MICEOSCOPE. 



part of the piece of brass, B B, is fixed a square stem, E E, the 

 posterior surface of which, r r r, is provided with a rack, by 

 means of which the supports, G, of the stage, P, and of the 

 mirror, H, can be raised or depressed. By this means the 

 coarse adjustment is formed, the fine being effected by the 

 screw, L L, which moves the stage up or down without 

 affecting the rack-work. The compound body, D, has a 

 draw-tube, Q, capable of being moved out or in by the rack, 

 R, and a pinion connected with the milled head, S. This 

 microscope is generally used in the position represented by 

 ■fig. 52, but when the tube, M, is removed, and a straight 

 piece to carry the object-glass is substituted, it may be con- 

 verted into a vertical microscope, by means of the joint C B, 

 or again into a horizontal one by the joint B C ; the prism, 

 m o, being for the purpose of bending the rays, so that 

 they may pass through the compound body. In order to 

 know when the stage, P, is perfectly horizontal, a stop, F, is 

 fixed to the bottom of the square stem, E E. The mirror, H, 

 like the stage, can be raised or depressed on the stem by rack 

 and pinion. 



THE MICEOSCOPE OF OBEEHAUSEE. 



M. Oberhauser, of Paris, constructs two kinds of micro- 

 scopes, one for dissection, the other for general purposes. 

 The former was described in the first edition of this work, the 

 latter is represented by fig. 53. It consists of a circular foot 

 or base, four inches in diameter, loaded with lead ; upon this is 

 fitted a stout tube, two inches high, on which the stage rests. 

 This tube has^an oblong opening in front for the light to fall 

 on the mirror, and the tube itself is capable of being turned 

 upon the foot, and the stage upon it, so that not only can 

 the light falling upon the mirror be put in any situation, but the 

 stage, and with it the object, can be revolved, so that rays, 

 however oblique, may be thrown upon all sides of any object. 

 To the stage is fixed the support of the compound body, in 

 which are contained the adjustments; the coarse effected 

 by rack and pinion, and the fine by a screw. A very coarse 

 adjustment is made by sliding the compound body up and 



