1 6 Mr. cavallo’s Account of fome 
The electropliorus, that is, a plate of fome re-finous 
fubftance, as fulphur, rofen, gum-lac, 8cc. is firft ex- 
cited, either by rubbing, or otherwise ; then a piece of 
metal of any fhape at pleafure, as, for inftance, a 
three-legged compafs, a piece of brafs tube, or the 
like, is fet upon the eleftrophorus ; and to this piece of 
metal, fo placed, a fpark is given of the electricity con- 
trary to that of the plate. This done, the piece of metal 
is removed by means of a flick of fealing- wax, or other 
eleCtric ; and fome powder of rofen, kept in a linen 
bag, is fhaken upon the eledt rophor us. This powder 
will be found to fall about thofe points upon the plate 
which the piece of metal touched, forming fome radiated 
appearances much like the common reprefentations of 
ftars; at the fame time upon the greateft part of the plate, 
that is, in all parts except where the ftars are formed, 
there is hardly any povcder at all. Now it is to be re- 
marked, that if the plate be excited negatively, and the 
fpark given to the metal fet upon it, be pofitive, the appear- 
ance will be as above defcribed ; but if on the contrary 
the plate is pofitive, and the fpark is negative, then the 
powder of rofen will be found to fall upon thofe parts 
of the plate, which in the other cafe are left uncovered ; 
and to leave the ftars clean : in fliort, it will do juft the 
reverfe of what it did in the other cafe : or, in other 
words, 
