ELECTRICAL FACTS. 
13 ? 
This explanation labours under the difficulty of its being hitherto 
far from being proved that such atmospheres have any exis- 
tence ; and likewise under that of the supposition of an uniform 
height of such atmospheres, and their disposition to fly off, 
without any other evident cause than an accumulation, which 
apparently ought to be preserved by the same cause which 
occasioned it, being entirely gratuitous. Volta ascribes the 
action of points to the minuteness of their surface, which does 
not admit any sensible quantity of the electricity to take the 
form of a charge,* as it always does in large surfaces, to the 
diminution of that intensity on which the disposition to escape 
depends. This explanation is nearly the same as if he had said, 
that the surfaces between which electricity passes, are the coat- 
ings of an electric plate of air, and that the transition consists 
in the breaking of this plate of air, as soon as it is highly enough 
charged j that the smaller the surface, the higher the charge, 
the same power of excitation or accumulation of electricity, 
being supposed, and, consequently, the thicker the plate of air 
which might be broken through, or distance to which the 
electricity would fly. That the escape or transition of electricity 
is prevented or rendered less easy by the diminution of intensity, 
produced by the vicinity of an uninsulated conductor is experi- 
mentally proved ; but it does not appear probable, that the want 
of this diminution is the p"incipal cause of the action of points. 
For if we suppose a round ball to be presented to an electrified 
conductor, at such a distance as that the diminished intensity 
should be insufficient to produce a communication of electricity, 
it ought to fallow, if the diminution were the principal cause of 
the communication not taking place, that a point at the same 
distance would cease to receive or emit electricity, as soon as 
its operation had produced as great a diminution of intensity as 
the ball had produced in the former case ; or that a ball, pre- 
sented at a given distance from a conductor, would prevent the 
operation of a point. But it is well known, that the facts by no 
means confirm this deduction, not to mention that a ball of a 
moderate size produces no sensible diminution of intensity in a 
large conductor well supplied ; and that, in many cases, pointed 
bodies perform their usual effect at great distances from other 
* Philosophical Transactions, vol. lxxii, p. 1. 
bodies 
