249 



which partly cover it. On each side of the uprights, over these 

 partial covers, are screwed two thick pieces of black walnut, with 

 holes for the eye-glasses on one side and the objectives on the 

 other. 



This box is open at one end to receive a flat-iron or other 

 weight, if required, and to admit the other parts when the in- 

 strument is packed. 



Between the uprights is received the bearing semicircle, made 

 of three pieces of black walnut glued together, the inner one hav- 

 ing the grain directed lengthwise, the two outer ones vertically. 

 This is provided with a " slot " partly vertical, partly horizontal, 

 and several notches. A binding screw holds it at any angle and 

 at various heights between the uprights. 



The microscope-tube, made heavy by a leaden tube inside, is 

 laid upon two V-shaped supports cut out of the wood, being held 

 solely by its weight when used in the horizontal or inclined posi- 

 tion. 



The microscope-tube has a ring an inch wide, fitting tight, but 

 becoming loose on pressing its handles, and having a little projec- 

 tion, or spur on the side opposite its handles, as shown in fig- 

 ure 2. 



The anterior V-shaped support is also shown in this figure. It 

 has a piece of brass let into the wood for the s'pur on the ring to 

 play against. As the posterior surface of this support is slanted 

 about one sixteenth of an inch, it is evident that in turning the 

 tube through a semicircle it will advance or recede that distance. 

 This turning of the tube is performed by means of the black 

 pasteboard disk clasped to the tube near the eye-piece, which 

 makes a sufficiently delicate fine adjustment. 



The horseshoe stage consists of two pieces of brass, cast and 

 planed, 4 inches across at the widest part, and 3 inches in height. 

 The first, nearest the observer, turns on a screw at the centre of 

 its semi-circumference against a brass plate screwed to the bear- 

 ing semicircle. The second turns on a screw which unites one of 

 its arms — the right — to the corresponding arm of the first horse- 

 shoe. The first horseshoe therefore carries the other with it ; 

 the second turning very easily, is moved independently of the first- 

 The handles are flat, the one with the cross next the observer, 

 the other projecting three quarters of an inch beyond it, so that a 



