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der-clouds in particular. The difcoveries of the de- 
monhrators of eledlricity, by wJiich they are en- 
abled, not only to determine its degrees of eledtrical 
force, which is produced by the rotation and fridtion 
of a giafs ball, but likewife thofe, that are emitted 
by thunder-clouds, are peculiar to him. And it 
mufi; be faid, to his honour, that he has made as 
many difcoveries on this fubjedt, as, I will venture 
to fay, any naturalift has ; and of which the learned 
world will be made more fenfible, by reading his 
treatife, when it comes from the prefs, which he 
intended to have read, the 6th of September, this 
year I7f3, at a publick meeting of the members of 
the academy. In order therefore to demonftrate what 
he might advance in this difcourfe with the greater 
certainty, he negledted no opportunity, upon the ap- 
pearance of a thunder-cloud, diligently to difcover 
its ftrength. Bars were ftanding for this purpofe 
always upon the roof of the houfe. Thefe received 
the eledlrical power of the clouds, and imparted it 
to certain chains faftened to them ; by which it was 
condudlcd into one of his rooms, where his appa- 
ratus was. He was attending the ufual meeting of the 
Academy the 26th of July a little before noon, 
when it thundered at a pretty diftance, the fky be- 
ing clear, and the fun Ihining. Upon this he haftened 
home, in hopes of confirming his former obferva- 
tions, or poffibly enabling liimfelf to make new 
ones. The engraver Sokolow, who had the care of 
his future treatife, accompanied him, to make him- 
felf the better acquainted with the chief circum- 
ftances of the eledbrical experiment, in order to be 
thereby enabled to reprefent it more jufily on a 
copper- 
