206 Mr. cavendish on the Torpedo. 
5y inches diftance between its fides and thofe of the 
trough. 
The battery was compofed of 49 jars, of extremely 
thin glafs, difpofed in 7 rows, and fo contrived that I 
could ufe any number of rows I chofe. The outfides of 
the jars were coated with tinfoil; but as it would have 
been very difficult to have coated the infides in that man- 
ner, they were filled with fait water. In a battery to 
anfwer the purpofe for which this was intended, it is 
evidently neceffary that the metals ferving to make the 
communications between the different jars fhould be 
joined quite dole: accordingly care was taken that the 
contads fhould be made as perfed as poflible. I find, by 
trial, that each row of the battery contains about 15^ 
times as much eledricity, when both are conneded to 
the fame prime condudor, as a plate of crown glafs, the 
area of whole coating is 100 fquare inches, and whole 
thicknefs is of an inch ; that is, fuch that one fquare 
foot of it fhall weigh 1 o oz. 1 2 pwts. ; and confequently, 
the whole battery contains about no times as much 
eledricity as this plater*;. 
The way by which this was determined, and which, 
I think, is one of the eafieft methods of comparing the 
quantity of eledricity which different batteries will re- 
(a) I find, by experiment, that the quantity of eledricity which coated 
glal's of different fhapes and fizes will receive with the fame degree of electrifica- 
tion, is diredly as the area of the coating, and inverfely as the thicknefs of the 
glafs j whence the proportion which the quantity of eledricity in this battery 
bears to that in a glafs or jar of any other fize, may eafily be computed. 
ceive 
