[ 650 } 
when it is furrounded on all lides by the air, as. 
no fluid can run out of it without running into 
the air, the fluid will not do fo without difficulty. 
If any body is furrounded on all fides by the air, 
or other noi>condu6ting fubftances, it is faid to be 
infulated : if on the other hand it any where com- 
municates with any condufling body, it is faid to 
be not infulated. When I fay that a body com- 
municates with the ground, or any other body, I 
be miderftood to mean, that it does fo by 
fbme condu6ling fubftance. 
Though the terms pofltively and negatively elec- 
trified are much ufed, yet the precife fenfe in 
which they are to be under flood, feems not well 
afcertained namely^ whether they are to be un^ 
derflood in the fame fenfe iiv which- I have ufed 
the words over or undercharged, or whether, when- 
any number of bodies, iirfulated and communi- 
cating with each other by conducing fubflances, 
arc elearified by means of excited glafs, they are 
all to be called pofitively elearified (fuppofing, ac- 
cording to the ufual opinion, that excited glafs 
contains more than its natural quantity of eleari- 
city); even though fome of them, by the approach- 
of a ftronger elearified body, are made under- 
charged. I fhall ufe the words in the latter fenfe; 
but as it will be proper to afcertain the fenfe in 
which I fhall ufe them- more accurately, I. fhalb 
give the following definition. 
In order to judge whether any body, as A, is 
pofitively or negatively elearified : fuppofe ano- 
ther body B, of a given fhape and fize, to be placed 
4 t an. infinite diflance from it, and from any other 
over. 
