FOE THE MICEOSCOPE. 



279 



Tig.l. 



of its length, at an equal 

 distance from either end 

 of it, is cut a spiral 

 groove, h i. The ful- 

 crum is at / on the left 

 side of the stage in a 

 small pillar rising out of 

 a slight projection from 

 the lowest plate of it, 

 and is so contrived, that 

 the lever can be easily 

 turned on its own axis. 

 On the other end of 

 this lever at g a milled 

 head is fixed, by which the different motions are given to the lever. 

 An enlarged representation of the adjustment for the fulcrum is 

 given at Fig. 2., representing a small brass pillar, which passing 

 through the under plate of the stage, is held down by a forked piece 

 of brass screwed to the under side of the plate, and accurately fitting 

 the neck cut in the pillar at o, so that the pillar can readily be turned 

 on its own axis while firmly held in its place. The end of the lever 

 having a similar neck, is shown at m ; this fits into the pillar and is 

 held in its place by a small forked piece of iron, n, passing down over 

 the neck, and secured by the small screw p. The grooved part of 

 the lever passes through a short brass tube, e ( Fig. 1.,) (an enlarged 



representation of which is given 



Mg.Z. 



~P liswh) 



Tig. 3 



at Fig. 3.) to this tube a small 

 stem r is attached, which screws 

 into the under side of the upper 

 stage plate by a left handed screw, 

 a small steel screw s passes 

 through the tube, the point of 

 which fits into the spiral groove 

 h i of the lever. The upper stage plate slides in dove-tailed grooves 

 made in a frame of brass, and this frame slides in the dove-tailed 

 grooves at a b and d c but at right angles to the former. The arm 

 which carries the compound body rises from the projection shown at 

 1c ; by turning the milled head g the action of the spiral groove on 

 the pin iu the tube e moves it, and with it the stage to which it is 

 attached, to or from the hand ; while by moving the milled head 

 backward or forward, a transverse motion is produced, and by com- 



