a new Electrometer, 
anfwering to the 90' , which the arm Gi moves through. The 
fhorteft end reaches to a fmaller circle, divided into 60 equal 
parts, anfwering to 60 grs. weight, or 60 divifions, on the arm 
(7 1, with its Hiding weight w, each of which is equal to one 
grain, and the whole face is covered with a watch glafs, to 
prevent the eleCtricity from flying off at the points. 
The top of the glafs-lupporter, or inlulator D, is cemented 
into a brafs cap M. This cap enters the ball L at bottom, and 
1 crews into the upper part of the ball L at a . The top part 
of this cap M is tapered off to a cone about an inch and a half 
long or high. The lower end of the wire H has a hole made 
conically into it, fo as to receive the upper part, or conical end, 
of the cap M, which permits all the upper part of the electro- 
meter to turn round any way that may be neceffary. The kind 
of ferrel O, with its bale, is perforated for the lower end of 
the wire II to go through. The bent arm which fupports 
the cup N, is lcrewed into the bafe of the ferrel O, and turns 
freely round upon the wire H. The cup N is to receive the 
ball P of the arm, fig. 9. This arm (hortens or lengthens, a3 
may be wanted, bv a wire Hiding into a tube. The end of the 
wire is Hit, forming a lpring in the tube to be ifeadv. hi this 
arm, fig. 9. is a kind of rule joint at d, that the arm may give 
way eafilv if wanted. The lemi-circular end of the arm is a 
lpring, and flips on to a ball from the prime-conduCtor, or the 
conductor itfelf (if they fit), jar, or battery. The ends of it 
are flat and broad, as reprefented in the drawing in miniature, 
of the electrometer at fig. 2. in the other drawing. 
Fig. 2. to 11. fhews the internal ftruCture of the electro- 
meter. 
Fig. 1 2. fhews the part at s that lerews into the ball F, to 
fupport the arm g with its ball r. This piece, which is made 
Vol. LXXII. E e e hollow 
