Chap. 4.3 'Electrometer. 337 



other light body, fufpended on a moveable arm, with 

 a kind of femi-dial to mark the degrees. Mr. Adams 

 recommends Mr. Henley's quadrant electrometer for 

 this purpofe, which he defcribes as follows : " It con- 

 fifts (Fig. 3. Plate XXVI.) of a perpendicular ftem 

 formed at top like a ball, and furnifhed at its lower 

 end with a brafs ferrule and pin, by which it may be 

 fixed in one of the holes of the conductor, as at Fig. 4. 

 or at the top of a Leyden bottle. To the upper part 

 of the ftem, a graduated ivory femicircle is fixed, about 

 the middle of which is a brafs arm or cock, to fupport 

 the axis of the index. The index confifts of a very 

 flender flick, which reaches from the center of the 

 graduated arch to the brafs ferrule; 'and to its lower 

 extremity is faftened a fmall pith ball nicely turned in 

 the lathe. When this electrometer is in a perpendi- 

 cular pofition, and not electrified, the index hangs pa- 

 rallel to the pillar ; but when it is electrified, the in- 

 dex recedes more or lefs, according to the quantity of 

 electricity." 



VOL. I. 



