Mr. cavendish on the Torpedo. 207 
ceive with the fame degree of electrification, was this: 
Firft of all, fuppoling ajar or battery to be electrified till 
the balls of the abovementioned electrometer feparated 
to a given dilfance, I found how much they would feparate 
when the quantity of electricity in that jar or battery was 
reduced to one-half. To do this, I took two jars, as nearly 
equal as poftible, and electrified one of them till the balls 
feparated to a given degree, and then communicated its 
electricity to the other; and obferved to what diftance 
the balls feparated after this communication. It is plain, 
that if the jars were exaCtly equal, this would be the 
diftance fought for; as in that cafe the quantity of elec- 
tricity in the firft jar would be juft half as much after 
the communication as before ; but as I could not be fure 
that they were exaCtly equal, I repeated the experiment 
by electrifying the fecond jar, communicating its elec- 
tricity to the firft, and obferving how far the balls fepa- 
rated; the mean between thele two diftances will evi- 
dently be the degree of feparation fought, though the 
jars were not of the fame fize. Having found this, I 
electrified one row of the battery till the balls feparated 
to the firft diftance, and repeatedly communicated its 
electricity to the plate of coated crown glafs, taking care 
to difcharge the plate each time before the communica- 
tion was made, till it appeared by the electrometer, that 
the quantity of electricity in that row was reduced to one. 
half. I found it neceftary to do this between n or 12 
times, or 11^ times as I eftimate it. Whence the quan- 
tity of eledtric fluid in the row may be thus determined*. 
Let 
