400 Mr. cavallo’s Experiments , See . 
advantages of this electrometer are, its convenient fmall 
iize, its great fenfibility, and its continuing longer in 
good order than any other I have yet feen, as you have 
yourfelf experienced To preferve this electrometer 
from injury, it ihould be carried in a tooth-pick cafe, or 
fome other of the like fort. 
(d) I have lately conftru&ed a portable ele&rometer of another kind, which 
is contrived fo as not to be affe&ed by the wind or the rain, and confequently is 
very convenient to examine the ele£lricity of the cloud* out of doors in time of 
thunder-ftorms : but I ftiall take another opportunity to prefent to the Royal 
Society a particular defeription of the fame. 
