810 



SUMMARY OF CURRENT RESEARCHES RELATING TO 



1 



ment by the usual screw acting against a spiral spring in the hollow 

 limb, as generally adopted in Continental models. The draw-tube is 

 graduated. The mirror (1) can either be used in the optic axis 

 as shown in situ, or an additional elbow-piece (2) fitting into the 

 hole (2) immediately below the stage can be made use of for giving 

 some range of obliquity, A condensing lens for opaque illumination, 

 fitted with jointed arms, can be attached to the side of the tube, and a 

 revolving plate of diaphragms beneath the stage. 



For convenience of packing the objective is removed, the draw- 

 tube closed, and the optical body drawn up the sprung-socket ; the 

 milled head shown behind the limb is then partly imscrewed, allowing 

 the stage to be turned laterally a quarter-turn, so that it lies parallel 

 with the limb, the optical body being slid down again as far as it will 



Fig. 170. 



go. The mirror and condensing lens are also removed, and the base 

 unscrewed, inverted, and placed in the travelling case, the under sur- 

 face — shaped in the casting — forming a secure packing for the instru- 

 ment as shown in Fig. 170. The whole is enclosed in a leather-covered 

 box 7|^ X 3 X If inches (about the size of a cigar-case), which can be 

 used as the foot, the Microscope being screwed to the lid instead of the 

 metal base, if it is not desired to be encumbered with the latter on 

 excursions, &c. 



Swift's "Challenge" Binocular Microscope (C). — This form of 

 stand (Fig. 171) — the type model of Messrs. Swift and Son — has had 

 their fine adjustment (described ante, p. 296) adapted to it, in which 



