60 PRACTICAL TREATISE ON THE MICROSCOPE. 



compound microscope by taking away the lens-holder and 

 substituting for it a compoimd body, and when provided with 

 a cradle joint, either at the top or bottom of the pillar, may 

 be inclined after the manner of the larger instruments pre- 

 sently to be described. 



This microscope, with its broad stage, is well adapted for 

 minute dissections, and is rendered more convenient for the 

 purpose if placed between two inclined planes, to be here- 

 after mentioned, which form what is called the dissecting rest. 

 This apparatus gives support to the arms, and brings the 

 wrist on a level with the stage, whereby small cutting instru- 

 ments can be managed with the greatest nicety. 



Another highly useful, and far more complete stand of a 

 simple microscope, for the dissection of minute botanical and 

 other objects, was contrived by Mr. Wm. Valentine, and 

 constructed for him by Mr. Andrew Koss, in 1831 ; it is fuUy 

 described in the forty-eighth volume of the Transactions of 

 the Society of Arts, and was one of the first simple microscopes 

 provided with a moveable stage, and with coarse and fine 

 adjustments, as represented by fig. 38. It is supported on 

 a firm tripod, made of bell-metal, the feet of which, a a a, 

 are made to close up together. A strong pillar, b, rises from 

 the tripod, and carries the stage, e, this is fiirther strengthened 

 by two brackets, r r. From the tube or pillar, a triangular 

 bar, d, and a triangular tube, c, slide, the one within the 

 other ; the outer or triangular tube, c, is moved up and down 

 by a screw, having fifty threads in the inch, turned by a large 

 mUled head, v, situated at the base of the piUar, this is the 

 fine adjustment. The small triangular bar, d, is moved up and 

 down within the triangular tube, c, just described, by means 

 of a rack and pinion, turned by the milled head, t, forming 

 the coarse adjustment: this bar carries the lens-holder, mnop. 

 The stage, e, consists of three plates, the lowest one is firmly 

 attached to the pillar, and upon this the other two work. 

 The upper one carries a small elevated stage, g, on which the 

 objects are placed ; this stage is mounted on a tube, f and 

 has a spring clip, h, for holding, if necessary, the objects 

 under examination. By means of two screws, placed diago- 



