Professor Leslie on Electrical Theories . 
9 
The ball A will, from its mere approximation, assume an opposite 
electricity, and therefore attract these particles ; but the action 
which it will exert must decrease rapidly with the distance. 
Let the ordinates FO, EP, X)Q, & c. of the curve SRQPO, 
denote the forces at F, E, D, &c. Let the attraction of A have 
its limit at B, which is so extremely near the surface, that, on a 
farther approach, the particle will receive the same electricity 
with the ball, and consequently be repelled. The ordinate BS 
will therefore be the greatest ; and, from S, the curve will ad- 
vance fast to the line AN, which will be its assymptote. 
Because the particle F tends to A with the force FO, and 
E to A with the force EP, E will be drawn from F with their 
difference XP. But if the pressure of E upon F be diminished, 
that of F upon G will be equally diminished ; and so will that 
of G upon H, of H upon 1, of I upon Iv, &c., whence all the 
particles will tend to A, with the force XP. Again, because E 
is attracted by the force EP and D, by DQ, D will be drawn 
from E by the difference WQ ; and thus the pressure of 1) upon 
E, of E upon F, of F upon G, &c. will be diminished by WQ ; 
and therefore these particles will tend to A with that force. 
Hence all the particles of the atmosphere will indiscriminately be 
urged to A, by the sum of the forces XP, WQ, UR, &c. or 
that denoted by the last ordinate BS ; and the electrified par- 
ticles will be moved by the additional forces expressed by the 
ordinates corresponding to their distances. 
Such are the forces that exist previous to the motions which 
they produce; but a different distribution must afterwards take 
place. For a particle at Y adjacent to N will, in consequence 
of its direction towards it, be brought into the position Z, nearer 
to M ; whence the density will be greater at M than at N, and 
gradually increase from N to A ; wherefore M will press upon 
N, by the difference of the elasticity, arising from the change of 
density. In the same manner, L will press upon M with the 
difference of elasticity between L and M, and which force will 
be communicated to N. By pursuing this mode of reasoning, it 
will appear that the original tendency BS of each particle of air 
to the ball A, will be diminished by the amount of the conden- 
* 
sations of all the intervening particles, occasioned by their mp- 
