504 



MICROSCOPY. 



gress" stand, by Ross & Co., in the Wenham 

 "Radial" stand (see Fig. 11), ("A. M. M. J.," 

 1883, p. 146), by Watson & Sons, in their in- 

 clining stand (" J. R. M. 8.," 1881, pp. 300, 516), 

 and by other makers. Lately a sliding fork, 

 holding the object-slide in place, has been pro- 

 posed as a substitute for the sliding object- 

 carrier; thus thinning the stage by dispensing 

 with one plate, and allowing the object-slide to 

 lie upon the bed-plate of the stage. The stages 

 are sometimes made reversible, to carry the 

 slide below for extreme obliquity of illumina- 

 tion, or are furnished with additional spring 

 clips below for the same purpose, the rotating 

 clips in Wale's " working " stand being also re- 

 versible and capable of holding a slide in any 

 azimuth either above or below the stage. An 



The mirror is supported upon a radial bar or 

 swinging tail-piece hinged in the plane of the 

 object on the stage. It therefore swings radi- 



FIG. 9. CLOCK-SPRING FINE ADJUSTMENT. 



additional inverted stage with clips has also 

 been made, to slip upward into the regular 

 stage-opening (" Amer. Jour, of Mic.," 1879, p. 

 92) ; but such devices are seldom required with 

 present thickness of stage (about inch, per- 

 mitting incidence of light up to 70 or 80) and 

 present means of immersion illumination. The 

 rack for rotating the stage is mostly aban- 

 doned, as all precision usually required can be 

 attained more promptly by hand ; but the cir- 

 cumference is graduated, in the better stands, 

 to indicate the extent of rotation. The stage 

 is set just high enough to admit the adaptation 

 of the sub-stage apparatus of the large English 

 stands, which apparatus is not attached to the 

 stage, but supported upon a ring or sub-stage 

 below. 



FIG. 10. WEDGE FINE ADJUSTMENT. 



ally to the object on the stage, which is 

 the optical center of the instrument ; and it can 

 thereby be placed with the greatest ease and 

 precision at any angle from the axis, either be- 

 low or above the stage, without altering its 



FIG. 11. ROUND STAGE; MECHANICAL. 



distance from the object, the extent of swing 

 being indicated, except in the cheapest form, 

 upon a graduated circle. The distance of mir- 



