f 
¢ 
160 ON A SYSTEM OF NOTATION ADAPTED TO EXPLAINING 
negative or resinous electricity ies bs to the glass passes over 
to the rubber, and an equal measu eof positive or vitreous passes 
to the glass. Each body sities to have the same quantity of 
Hectic fluid attached 4 it as at first, but the iiss lity of the fluid 
is changed—each body has now an excess of one fluid, and a 
corresponding deficiency of the other—and otNsg each body 
is electrically excited or charged, the one positively and the other 
negatively. 
now the case of the urigd sehgn When the metal 
cover is put down on the excited cake of resin, the compound 
fluid of the cover is pans osed by induction, it po ositive portion 
being attracted towards the cake and its negative repelled. If 
the cover be touched by a conductor, a part o of the repelled nega- 
 eX#ESS 0. posi sitive, and when the cover is patente from the 
inductive action of the cake and touched with a conducter, it 
gives off its excess of positive and receives an equal amount of 
negative, thus restoring the oO condition of the cover. Let 
us see how these changes may be simply represented. 
oe. V be a measure of ieits or ad sates electricity, and R 
an equal measure of resinous or negative; V + R will then 
represent the neutral fluid. If we take the ‘fluid on the surface 
of the resinous cake to b may suppose it to be 
entirely decomposed by friction, and it will then become 2 R. 
Represent the fluid of the cover thus : vie The cover being 
put down on the cake, the whole fluid will be decomposed by indue- 
tion and we shall have pes Touch the cover with the finger. 
The 2 R of the cover 6 2 V from the finger ; they combine, 
and the neutral fluid thus formed is instantly distributed on the 
contiguous surfaces, V 4+ R going to the cover and the same to 
the finger. The cover will then show ¥: Ait , V being in excess 
and R deficient. Remove the cover by its insulating handle an 
touca it—YV is given off, and R received in its place, leaving the 
Wid R 
cover as at first : ' 
rave R. 
In Dr. Golding Bird’s “Elements of Natural Philosophy”. 
modification of Volta’s electrophorus is thus described :—“ thin 
with amalgam; then carefully lifting the glass by one 
corner, place it on a badly condueting surface, as dese este 
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