B$4 Mr Ronalds on a Pendulum Doubler of Electricity . 
the centre of the plate A, the insulated bent wire will touch, 
at the same moment, the ends of the wires m and n , and esta- 
blish thereby, a metallic communication between A and B ; and 
that the wire i, by touching the wire o at the same moment also, 
will establish a communication between C and the earth. Now, 
by one of the laws of induction or compensation, — i. e. that pro- 
perty which any insulated conducting surface possesses, when 
placed opposite to an uninsulated conducting surface, with a 
plate of air (or other semi-conducting or insulating body) inter- 
posed, of condensing on, or attracting to itself (within certain li- 
mits) the electricity which has been given to insulated conductors 
in communication with it, and , being thus charged , of inducing 
a contrary state of electricity on the uninsulated opposed sur- 
face. , — by this law of induction, I say, if a quantity of positive 
electricity, producing a tension — 1 degree in the electrometer, 
be given to either A or B, whilst the centres of A and C are 
opposite to each other, that quantity will be nearly all condensed 
pn A, and C will have a tension nearly 1 of negative electri- 
city. 
44 If C be now allowed to begin its vibration, the connection of 
A and B with each other will be instantly broken, as also that 
of C with the earth, and they will be all insulated, and all re- 
taining the electric states which they possessed before the con- 
nections were broken (i. e. A will be positive nearly = 1 ; B ne- 
gative nearly = 1 ; and C positive almost 0.) 
44 When C has arrived opposite to B, the uninsulated wire h 
will touch the wire 7, and thus place B in connection with the 
earth ; therefore C, by virtue of its negative charge, will induce 
a positive charge in it nearly — 1. 
44 When C arrives a second time opposite to A, all the former 
connections will be re-established, and the charge of B will (by 
means of the wire m) be nearly all condensed on, and added to 
the original charge of A, making a tension nearly = 2 of posi- 
tive electricity, which tension will induce a tension nearly = 2 of 
negative electricity on C. 
44 When C arrives again opposite to A, the same process recurs 
as before ; and, when it returns a third time to A, the charge of 
B, being added to A, will produce a tension nearly = 4. 
44 And so the charges in A and C would go on, nearly doubling 
