ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 



243 



can be fitted above the rotating stage. The coarse-adjustment is by 

 rack-and-pinion. The fine-adjustment (fig. 38) is by means of a new 

 micrometer-screw, which operates thus : by turning the milled head m a 

 spindle on which a worm is cut actuates a worm-wheel, by the rotation 

 of which a roller is raised or lowered, and with it the tube. In this 

 manner a fine-adjustment of the greatest delicacy is attained. The 

 movement of the micrometer-screw is an endless one, which is a feature 

 of considerable importance. Since the only downward pressure is that 

 of a delicate spring and the slight weight of the aluminium tube, the 

 resistance to the micrometer-screw is exceedingly small, and injury to the 



Fig. 38. 



cover-glass is almost impossible, even should the objective come into 

 contact with it. All bearing surfaces are of steel, and the entire 

 mechanism is protected within the frame of the Microscope. The head 

 of the micrometer-screw is so graduated that one division is equivalent to 

 • 001 mm. movement of the objective. 



Reichert's Large Stand, No. 1 A, fitted with Tip-up Stage-Clips.* 

 The movable object-stage of this instrument (fig. 39) was figured and 

 described in the Journal for 1898 (p. 383, fig. 43), but attention was 

 not called to the tip-up stage-clips, which are here seen in position. 



* C.Reichert (Vienna), Catalogue No. 25 (Mikroskopie, 1904) pp. 17-18 (figs. 

 4, 4a). 



