THE MICROSCOPE AND ITS REVELATIONS. 



ment may be firmly steadied in positions more or less inclined, or may be 

 fixed upright. It may be also fixed in the horizontal position required 

 for drawing with the Camera Lucida; for the pin at the bottom of the 

 stem then enters the hole at the top of the stud K, and the stay a falls 

 flat down, resting on the top of the stout pin L. The advantages of this 

 construction are that it is strong, firm, and yet light; that the instru- 

 ment rests securely at the particular inclination desired, which is often 

 not the case on the ordinary construction when the joint has worked 

 loose; and that in every position there is the needful preponderance of 

 balance. The Stage D is circular, and upon it fits a circular plate T, 

 which rotates in the optic axis of the Microscope. On the plate T there 

 slides the Object-holder u, which is so attached to it by a wire spring 

 that bears against its under surface, as to be easily moved by either or 

 both hands; and as access can be readily gained to this spring by detach- 

 ing the plate T from the stage, it may either be removed altogether so as 

 to leave the stage free, or may be adjusted to any degree of stiffness 

 desired by the observer. The object-holder has a ledge v for the support 

 of the slide; and it is also provided with a small spring w, attached to it 



by a milled-head, by turning 

 - 49 * which the spring may be 



brought to bear with any re- 

 quired pressure against the 

 edge of the slide laid upon the 

 object-holder, so as to prevent 

 it from shifting its place when 

 rotation is given to the stage, 

 or when, the instrument being 

 placed in the horizontal posi- 

 tion, the stage becomes verti- 

 cal. The central tube of the 

 Stage is furnished with a rota- 

 ting Diaphragm-plate, and is 

 adapted to receive various 

 other fittings; and a Side-Con- 

 denser on a separate stand is 

 also supplied. 1 



67. Collinses Harley Bin- 

 ocular. This instrument, as 

 represented in Pig. 49, is sub- 

 stantially framed and well 

 hung on the Eoss model; but 

 is now made also on the Jack- 

 son model at the same price. 

 The caps of the Eye-pieces are 

 provided with shades, which 

 cut off the outside lights from 

 each eye; these can be adapted 

 to any instrument, and the 

 Author can speak strongly of 

 their value from his own ex- 



Collins's Harley Binocular. 



1 The price of this instrument, with two pairs of Eye-pieces, three Objectives 

 (a 2-inch of 10, a 1-inch of 22, and a l-4th of 75), and Side-Condenser on stand, 

 in Case, is 16 10s. 



