in EleBritity , 66 J 
other mathematical inftrument-makers Since that time 
great ufe has been made of thefe eleCtrical plate ma- 
chines throughout Europe, as they were thought by 
many to be more powerful in a little compafs than thefe 
with globes and cylinders. 
In my travels through different countries, I now 
and then met with confiderable improvements made ill 
them. Abbe fontana had contrived one for the cabinet 
of the great Duke of Tufeany, which confifted of two 
plates, eighteen inches diameter, fixed to the fame cen- 
ter, and each rubbed on both fides on two oppofite places. 
The eleCtrical fire excited on thefe joint plates, when 
forced upon a conductor divided in two branches to re- 
ceive it, was very powerful; fo much fo, that the con- 
ductor, being unable to contain the whole, threw it back 
upon the brafs center; from which it paffed to the hand 
of the operator, and gave him a very difagreeable fhock. 
Mr. cuthbertson, an ingenious mathematical in~ 
ftrument -maker at Amfterdam, Contrived an apparatus- 
with a double plate, by which all the eleCtrical fire col- 
lected by the eight cufhions was forced Upon the con- 
ductor, fo that none of it could be thrown back upon 
the center, though made Of brafs* His contrivance con- 
fifted in placing between the glafs plates a ftfong glafs 
ring, about two inches in diameter, fo that the brafs 
4 R 2 center 
