On Electrical Influence. 37 
Such experiments prove (and have been long considered 
as proving) that there are two methods by which electrical 
effects may result from the action of an electrified surface 
en any insulated conducting body: Ist, by the communt- 
cation of its own electric state by immediate contact ; and, 
adly, by its influence on the distribution of the natural 
electricity in the insulated conductor when approximated 
to it. : 
By the first method, a positive surface can only com- 
municate positive electricity, and a negative surface, nega- 
tive electricity; and in either case the original electrified 
surface has the intensity of its electrical state diminished, 
and the communicated electricity is permanent (the insu- 
lation being supposed perfect). 
By the second method (approximation without contact) 
the insulated conductor is contrarily electrified at the ex- 
tremity nearest the electrified surface, but evinces the same 
electricity as that surface, at its remote extremity. 
This method of producing the contrary electrical states 
at the opposite ends of an insulated conductor, depending 
entirely on the unequal distribution of its natural electricity 
by the approach of an excited surface (with which it has 
no conducting communication), does not diminish the in- 
tensity of that surface; and for the same reason produces 
no permanent effect; the electrical appearances that were 
produced by its approach being destroyed by its removal. 
Electricity by approximation is therefore as transient as 
the cause by which it is produced. 
As direct contact of an electrified surface communicates 
permanent electricity of a similar kind} so the opposite 
electricity may be communicated by combining the me- 
thods of approximation and contact. Let the different 
states of electricity be excited in an insulated conductor by 
the approach of an electrical surface. Touch the conductor 
(during the continuance of these effects) with any tnin- 
sulating substance; its electric appearances vanish, though 
it still remains in the proximity of the electrical surface. 
Remove it from that proximity, it again appears electrified ; 
but it is now uniformly and permanently so, and its electri- 
city is opposite to that of the excited surface to which it 
was first opposed, and is therefore got derived from that sur 
face ; but from the uninsulated substance with which it 
came in contact during the disturbance of its natural elec- 
tricity. 
It is by this last method vey the opposite W goeady 8, 
,3 that 
