io Mr. Cavallo’s Obfervations on 
experiments of a very delicate nature, efpecially on animal 
bodies and vegetables, which could not have been attempted 
before, for want of a method of afcertaining exceedingly 
fmall quantities of electricity ; but, after a great deal of trou- 
ble, and many experiments, I was at laft forced to conclude, 
that the doubler of eledricity is not an inflrument to be de- 
pended upon, for this principal reafon ; viz. becaufe it multi- 
plies not only the eleCtricity which is willingly communi- 
cated to it from the fubftance in queflion ; but it multiplies 
alfo that eleClricity which in the courfe of the operation is 
almofl unavoidably produced by accidental fridlion ; or that 
quantity of eledlricity, however fmall it may be, which ad- 
heres to the plates in fpite of every care and precaution. 
Having found, that with a doubler conflrudled in the above 
defcribed manner, after doubling or multiplying twenty or 
thirty times, it always became flrongly eleClrihed, though no 
eleClricity had been communicated to it before the operation, 
and though every endeavour of depriving it of any adhering elec- 
tricity had been pradlifed ; I naturally attributed that electricity 
which appeared after repeatedly doubling, to fome friction 
given to the varnifh of the plates in the courfe of the opera- 
tion. In order to avoid entirely this fource of iniflake, or at 
leaf!; of fufpicion, I conflruCted three plates without the leaft 
varnifh, and which, of courfe, could not touch each other, 
but were to fland only within about one-eighth of an inch of 
each other. To effeCt this, each plate flood vertical, and was- 
fupported by two glafs flicks, which were covered with fealing- 
wax : fee Tab. I. fig. i. and 2., where AB is a wooden pe- 
deflal, 7 1 inches long, 2I broad, and i£ inch thick; C and D 
are the two glafs flicks cemented into the Hand or pedeflal AB, 
and likewife into the piece of wood E, which is faflened to the: 
back 
