72 THE MICROSCOPE AND ITS REVELATIONS. 



prism. The stage rotates in the optic axis; and may either bear (as in 

 the figure) a sliding object-carrier, or may be furnished with mechanical 

 actions. The mirror is attached to the stem by a crank-arm, allowing it 

 to be so placed as to reflect light of considerable obliquity. Beneath the 

 Stage is a broad horizontal dovetail groove, into which is very exactly 

 fitted a firm (sprung) slide that carries a Sub-stage for illuminating appa- 

 ratus, fitted with a vertical rack movement, and with horizontal center- 

 ing screws; this arrangement (devised by Mr. Swift) enables the sub- 

 Tic. 51 



Browning's Smaller Stephenson Binocular. 



stage to be placed in position or removed, without disturbing- either the 

 stage or the mirror. The extremely ingenious Universal Bub-stage 

 combining Achromatic Condenser, Black-ground Illuminator, and Pola- 

 rizer with varied adaptations devised by Mr. Swift for this Microscope, 

 but capable of being applied to any other, will be described hereafter 

 ( 112). The Author, having had his instrument (thus fitted) in constant 



