[ 463 ] 
from it into the balls, by the repulfive power of the 
fluid appertaining to the excited glafs. 
In thefe experiments we alfo learn, that when the 
glafs is held neater to the wood, than in the minus t 
and farther from it than in the plus appearance of the 
firfl experiment, it does not produce any eledric figns 
whatever in the balls. Which fliews a kind of ba- 
lance fubfifting between the power of the glafs, and 
the ref fiance of the wood, &c. For, if we deviate the 
leaf! on either fide from this intermediate diflance, 
eledric effeds, of the one kind or other, immediately 
take place. 
I fhall produce another experiment in favour of 
thefe forces, and of the ballance obtaining between 
them, in certain circumflances. In the experiment I 
am about to mention, it is neceffary, firfl to eledrify 
the wood and balls; by properly rubbing that end 
of the fealing-wax, amber, or glafs, to which they 
are affixed. 
You know then, that, if we touch the balls with 
the hand, we immediatly uneledrify them, and the 
wood; but not the amber : and that thefe balls with 
the wood, will continue uneledrified. But if I blow 
ever fo gently again/ t that part of the amber which is 
eleCt rifed y the balls will be feparated to a conjiderable 
dijiance , and continue in that date. On the other 
hand, if the amber has not been rubbed , no electricity 
can be produced by the fame force of blowings or even 
by a blafl fix or eight times greater : but if the blaflis 
confiderably increafed, the amber will be eledrified*. 
By which it appears that in the firfl cafe, the eledric 
power in the amber receives fuch an additional force from 
* See the letter to Dr. Heberdcn, page 332, 
O 0 0 2 
the 
