Professor Leslie on Electrical Theories . 
discharge is made through a thick wire two or three inches long., 
or through one of as many feet. Hence, also, no sensible varia- 
tion is occasioned by altering the size of the ball which termi- 
nates the discharging rod ; but if it be tapered to a point, the 
sound will become dull and obscure, and the more so as the 
point is made more acute. 
By comparing such experiments, we shall find, that the dif- 
ferent substances differ astonishingly in their conducting quali- 
ties. Thus, when the length, thickness, and other circumstances 
remain the same, the electricity is transmitted some hundred 
times faster through linen-thread than through fir-wood ; seve- 
ral hundred times faster through the metals than through water, 
&c. Hence, also, we may understand the nature of what is 
called a lateral discharge. For electricity is alike conducted 
through all the substances that form the communication ; only,, 
during the given time of the discharge, the quantities sent through; 
each are proportional to their celerity of transmission. It is 
thus that we scarcely feel any impression when we discharge 
by holding a chain : but, if we dip both hands in water that 
forms the communication, we receive a violent shock *. 
But the most important subject is to ascertain the effects pro- 
duced on the conducting substance. If the electricity is diffu- 
sed uniformly through it, the internal particles will be urged 
by an equal repulsion on all sides, and therefore must continue 
at rest. Those on the surface only will be pressed outwards ; 
but, if surrounded by air, the forces must be counterbalanced 
by the repulsion of the electrified aerial particles. However, 
if the electricity be unequally diffused, the equilibrium of for- 
ces will be destroyed. For if the particles B (PL I. Fig. 12.) repel 
C with a force, BX and D repel C with a force DL, the diffe- 
rence IM will tend to disunite the particle C. The total exer- 
* In farther illustration of this doctrine , it may he mentioned , that the common ex- 
periment of firing gunpowder inclosed in a quill , having a wire inserted at each end , 
will very seldom succeed , even with a strong electrical shock ; but if the circuit he 
partly formed by a column of water contained in a narrow glass tube, the transmission 
of only a moderate charge will never fail to cause explosion. Here the mutual repul- 
sion among the particles of the gunpowder is, in consequence of the retardation from the 
aqueous connection, exerted during a portion of time sufficient for commencing their 
chemical transformation. 
