DISSECTION OF VEGETABLE TISSUES. 



355 



the magnifying power of the microscope can also be greatly 

 reduced by the employment of the erector. M. Oberhauser, 

 of Paris, has constructed a microscope on this principle, for 

 the purposes of dissection, in which only one object-glass is 

 required for all variations in the magnifying power, from 

 eight to one hundred and thirty-five diameters. This instru- 

 ment is represented by fig. 235, and consists of a circular foot 



or base, a b, four inches in 

 diameter, with which is con- 

 nected a stout tube, c, two inches 

 high, supporting a stage, e, the 

 internal part of this, F, being of 

 black glass unpolished ; the tube, 

 c, is capable of being turned 

 on the foot, a b, and the stage, 

 e, together with the compound 

 body and its support, g h, can be 

 turned upon it. The tube has 

 an oblong opening in front, one 

 inch and a half broad, to allow 

 the light to fall on the mirror, m, 

 and by the motion of the tube 

 on the foot, this opening can be 

 placed in any position to receive 

 the light without turning either 

 'a the compound body or the foot 

 in the same direction. The 

 mirror is inclined at any angle 

 by means of the milled head, d. 

 The stage is somewhat like a battledoor in shape, and to the 

 narrow part, forming the handle, a strong support, g, for the 

 compound body, h, is firmly attached. The compound body 

 itself is composed of three tubes, A 1 K, sliding one within the 

 other, the outer one, h, serving for the attachment of all three 

 to the support, g. The next tube, I, carries the object-glass, 

 o, and is moved up and down by rack and pinion, the latter 

 being connected with the milled head, L ; by means of this 

 the focal adjustment is made. The third tube, K, carrying the 

 23* 



Fig. 235. 



