DESCRIPTION OF DR. CORING** ENGISCOPE. 169 



customary manner, but the socket has a slit for the neck 

 of the ball, only through one-quarter of a circle, to avoid 

 weakening it unnecessarily. It is pinched by a screw, ^, 

 with a vice-handle. The ball, the socket of the circular 

 bar, h, together with the stage-pin, i, are all cast in one 

 piece, as shewn in plan, fig. 8. The stage, j, has a cir- 

 cular aperture, which has a sink and two nicks in it, 

 together with a square hole, k, (as seen in fig. 9). There 

 is likewise an arrow pointing to a nick in the socket, 

 h, to shew when it is truly at right angles to the bar, b. 

 It fixes on to the pin, i, which is clamped tight by a 

 screw, / : into the bottom of this screw is inserted a 

 piece of metal, the end of which is worked to correspond 

 to the curve of the pin, i 9 which causes it to clamp tight 

 with a very slight effort, and preserves the pin from iii- 

 jury. Within the socket, h, is soldered a stout tube, 

 forming the external bar, c. On this circular bar slide 

 the split sockets, m, m, m, carrying the condensing lens, n, 

 the inferior pin, i, for holding the stage, and the oval 

 mirror, o : all travel up and down at pleasure, and may 

 either be moved out of the way, by turning them one- 

 quarter round, or stripped off altogether, if thought more 

 convenient. Their clamping screws fix them tight in 

 any required position. A nick is made in front of each 

 of the sockets, and a line drawn on the front of the bar, 

 to shew when the condenser and mirror, &c. are truly in 

 the axis of the aperture of the stage. The oval mirror is 

 plane, but its reverse is formed of plaster of Paris. It re- 

 volves on a vertical axis, p, and on a horizontal one, q y 



