2^ a D-cfcription of a nezv Elechometer, 



(of a certain fizc) in grains, and alfo cfiecl the clifchargc of 

 a l)attcry at the fame time. The inRniment known by the 

 name of Cuthbertfoa's difcharging eleilrometcr was at that 

 time the bell, and indeed the onJy inllrumcnt for difcharging 

 batteries or jars by its own adion, then made ; but I think 

 this will be found in the eirenlials, and in tlie theory and uie,^ 

 a more perfci^ inllrument. 



On the bafe S (fig. i. Plate VI.) Is fixed the glafs jiiOar G, 

 fupportin<r the hollow brafs ball B, T, is a light graduated brafs 

 tube divided (from the weight W towards the ball B) into thirty 

 parts, rcprcfcnting grains. W, is a Aiding weight. L, a light 

 brafs ball fcrcwed to the end of the tube T, on the other end 

 of which tube adjufls the heavy counter balance-ball C, the 

 tube T and its two balls being fufpended at their common 

 centre of graviiv by a (ilk line in the centre of the balJ B, the 

 Diechanihn of which is fliown in fig. a. The brafs ball F is 

 ftationary, and of the fame fize as the ball L, and is fixed by 

 a brafs arm to the ball B. The adjuillng ball A is alfo of the 

 liime fize, and adjufts clofe to the ball L, or at any lower Ihiliuu 

 between that and the ring r. The brafs tube to which the ball A 

 is fixed is divided into inches, halves, and quartrrs : (a more 

 minute divifion is unnecelfarv and improper.) The divifions 

 begin, or the o line is marked, on the faid tube at the ring r, 

 when the three balls ALF are clofe together. The ring r 

 ferves as an index, as tlie divifions pafs in fuceeilion into the 

 glafs tube P on lowering the ball A. The hook 11 is fcrewed 

 uito the bafe of P. The quadrant, or Henley's electrome- 

 ter, Q, is fupported on a long brafs ftcm to keep it out of the 

 atmofphere of the lower part of the inflrument. Fig. 2. 

 fliovvs the internal conftru6iion of the ball B., fig- i. In the 

 lirll place, the ball fcrcws in half, horizontally. The light 

 tube T pafles through the ball, and is fufpended nearly in the 

 centre of it bv fome filk twift s, which fmall filk twift is 

 fixed into the eye of the adjufting wire a, part of which wire 

 is filed fquare and goes through the fiiuare hole h. The 

 nut n fcrews on a, and ferves to adjufi: the light tube T ver- 

 tically. The light plates P P are of copper, and move 

 freelv on the wire ■zviu fomewhat like a hinge, and reft on 

 the copper wires CC, ferving to make the direft communi- 

 cation between the infide and out of the battery or jar. 

 K N are notches ferving to let the tube T defcend when the 

 difcharge is made. Into the tube Z the glafs pillar is ground. 

 Note, that at the bottom of the notch N is a piece of brafs 

 filed v/ith a Y, and fo placed as to keep the centres of the 

 balls L and F, fig. i, under each other when they come clofe 

 tt)crether- 



When 



