SJO COMPOUND ELECTRICAL INSTRUMENT. 



^o^d^"^f"* This inflrument ferves the piirpofe of a condenfer, a finglc 



fingle and double ^"^ double multiplier, and a doubler of eledlricity. When it 

 multiplier, and a js ufed as a fingle condenfer, ihe plate B is brought as near A as 

 cicftricity. *'^® fcrew 2 will permit, and then the wires b and/ touch one 

 another and uninfulate B, which increafes the capacity of A, 

 As the capacity of A is increafed it will receive a greater charge 

 of eledricity from any electrified body brought into conta(fl 

 with it. Confequcntly, when B is removed, the charge on A 

 will be much more intenfe than it would have been if the plate 

 B had not been oppofed to it ; but this intenfity will not be 

 greater than that of the eledrified body, if its furface is not 

 greater than the furface of the receiving plate A ; for a con- 

 denfer does not increafe the quantity of eleftricity, it only col- 

 Ie<5ls it into a fmaller fpace than it was before. So that if the 

 1 eledricity of a very (mall body is required to be afcertainedf 



the fimple condenfer will not anfwer the purpofe. Some other 

 means nluft be ufed when this is the cafe, and CavalIo*s multi- 

 plier is the lead exceptionable of the inftruments ufed for this 

 purpofe. The inftrument reprefented in the drawing forms a 

 multiplier, either fingle or double, for when B is near A and 

 uninfulatcd, A will receive a much greater charge that it would 

 if B had not been near. And becaufe B is uninfulated, A will 

 Induce a contrary flate on B, and of nearly equal intenfity; 

 which flate is preferved: For the infiant the lever is moved to 

 carry B farther from A; the contad between the wires />and/ 

 is difcontinued, and B infulated, and as it removes farther 

 away from A, the intenfity of its charge will increafe the fame 

 as that of A will, and be ready to part with nearly the whole 

 to another condenfer. 



Now as the plate B removes away from A, the plate D ap- 

 proaches C, and when at a fmall diftance from it, the wires d 

 and g come into contact, which operation uninfulates D, and 

 therefore caufes the two plates C and D to form a condenfer; 

 anfl at the fame inftant that d touches g, the wires h and c touch 

 one another, fo that nearly the whole of the charge of B is 

 communicated to C, which induces a contrary ftate on D, as 

 the charge of A did on B. D will therefore be in the fame 

 Hate as A is, which ftate is preferved; for the infiant the plate 

 B removes away from near C, the plate D alfo removes away 

 from it, and the contadt between the wires d and g is difcon- 

 tinued, and D infulated; and by continuing the motion the 



plate 



