J^evj univerfal Ele^rometey, 5,29 



{Tiould by any means receive a very low charge of ele£tric fluid, the two balls b, B, will repel 

 each other; B will begin to afcend, and, on account of the centre of gravity being above 

 the centre of motion, the afcenfion will contiuue till A reft upon a. If the balance be fet 

 again horizontal, and a pin 7, of any fmall weight, be put into its place in B, it will 

 caufe B to reft upon b, with a preflure equal to that weight, fo that more eletflric fluid muft 

 be communicated than before, before the balls will feparate; and as the weight in B is in- 

 creafed or diminiflied, a greater or lefs quantity of eleftric fluid will be required to efFedl a 

 feparation; 



When this inftrument is to be applied to a jar, or battery, for which purpofe it was in- 

 vented, one end of a wire, L, muft be inferted into a hole in b, and the other end. into a hole 

 of any ball proceeding from the infide of a battery, as M * : k muft be fcrewed upon c, with 

 itsindex towards A-, the reafon of this inftrument being added, is to fliew, by the index con- 

 tinuing to rife, that the charge of the battery is increafing, becaufe the other part of the in-- 

 ftrument does not adl till the battery has received its reqiiired charge- 



If this inftrument be examined with attention,, it will be found to confift of three elcGro-- 

 meters; and anfwers three different purpofes,. namely, a Henly's ele£trometer, Lane's dif- 

 charging electrometer, and Brooke's fteelyard eledlrometer; the firft not improved,' but the two 

 laft, which were very defedive when firft invented, I flatter myfelf are here brought to per- 

 fection. As the only ufe of Henley's eledlrometer to this inftrument is, as I have faid before 

 to ftiew, by its continuing to increafe in divergency, that the battery continues to receive a 

 ftill ftronger charge, it required no improvement ; but Lane's electrometer, in its primitive 

 ftate, could by no means anfwer the required purpofe for batteries, becaufe the ball intended 

 to difcharge the battery, was neceflliirily placed fo near to the ball of the battery, that duft and. 

 fibrous particles were always attraCted by and adhered between the two balls, fo as to retard 

 the charging, and often render a high charge impoflible : whereas, in this, they are placed at 

 four inches afunder ; and when the defired height of charge is obtained, and not before, the 

 ball of the eleCtrometer moves of itfelf nearer to the ball which is connecSted with the outfidc 

 of the battery, and caufes a difcharge. The defeats in Brooke's fteelyard eledrometer were, 

 ift, that it could not caufe a difcharge, and adly, the difficulty of obferving the firft feparation 

 of the balls caufed great error. If it were not placed in an advantageous light (which the 

 nature of the experiments could not always permit), it would not be feen, without the at-;- 

 tention of an afliftant, which is fometimes unpleafant, and cannot always be commanded. But. 

 the inftrument which I have defcribed, requires no attention or affiftance; for as foon as the 

 feparation takes place between B and b, the ball A defcends, and difcharges the battery of 

 itfelf. 



By this combination and improvements, we poflefs in the prefent inftrument 'all that can 

 ever be required of an eledrometcr ; namely, by k, we fee the progrefs of the charge ; by the 

 feparation of B, b, we have the repulfive power in weight ; and by the ball A, the difcharge 

 is caufed, when the charge has acquired the ftrength propofed. / 



* A chain, or wire, or any body through which the charge is to pafs, muft be hung to the hook at m, 

 and carried from thence to the outfide of the battery, as is rcprefcnted by the line N. 



Experiments 



