[ 339 ] 
fomething in the phenomena of electricity, not to be 
relolved, but upon ftatical pnnciples ; snd enabled 
me firft to affert, that the phenomena in bodies 
eleCtrifed, however fimilar they might appear, did 
really ari kjrom their electricity being either greater or 
lef s than their natural quantity. This doCtrine has, 
fince that time, been the caufe of a vaft variety of 
experiments, both here and abroad, by which great 
licrht has been thrown upon this part of natural phi- 
lofophy. How far our author has been able to over- 
turn this doCtrine, muft be left to other judges to de- 
termine. 
In the fourth letter, the doCtrine of refinous and 
vitreous eledricity is examined. In this letter, as 
well as in the fifth, a great number both of experi- 
ments and deductions are produced, not only to 
weaken the dodrine of plus and minus, but to efta- 
blifh the principle of ’ Jimultaneous affluence and effluence 
of eleCtric matter ; as, if this principle is allowed, the 
doCtrine of refinous and vitreous electricity may be re- 
duced to it : as our author is of opinion, that there is 
only one and the fame kind of electricity, whether it 
is natural or artificial j and that, however appearances 
may make it feem to vary, the electricity is one and 
the fame. 
The fixth letter is an anfwer to one of Father Bec- 
caria, profeffor of experimental philofophy in the uni- 
verfity of Turin, published in Italian, in the year 
17 r 3, and addrefi'ed to the Abbe Nollet. This 
letter of Fere Beccaria was tranllated into French, 
and publifhed at Paris in 1754, by M. Delor, with 
many additions and annotations. It contains a very 
^reat number of curious experiments and obfervations, 
Xx 2 both 
