on the Eleclrophorus. 1045 
take place, that is to fay, when the upper plate is taken 
off the cake in a pofitive ftate, the metal under the cake 
rauft be found in a negative ftate, if the electrophore be 
placed upon an electrical ftand. 
It may be afked, what difference there is between an 
eleCtrophore and a coated phial, or a flat glafs coated on 
both tides and charged ? I anfwer, that there is none at 
all, if both or only one of the metallic coatings can be 
taken off by filk firings, a piece of fealing wax, or any 
other infulating fubftance. The very fame day I received 
the eleCtrophore fent to me by his Royal Highnefs the 
Archduke Ferdinand from Milan (which electrophore 
was a thin refinous cake ftuck upon a flat piece of metal, 
to which was adapted a metal plate furnifhed with a glafs 
handle to lift it up) I produced the fame appearance by a 
common pane of glafs and the metal plate of the eleCtro- 
phore ; but foon finding that glafs, however dry, quickly 
lofes its eledricity (probably from its eafily attracting 
moifture from the air) I tried to cover it with a refinous 
fubftance, or to varnifh it over with a hard copal var- 
nifh ; by which means it was eafily excited by friction, 
and retained a long while the eleCtrical power, though 
not fo long as the refinous cake. 
I will now explain the nature of an eleCtrophore in a 
manner more familiar to electricians, who underftand 
the. 
4 
