Sir W. Snow Harris’s Researches in Statical Electricity. 177 
measures of electricity, the opposite plate b bemg turned aside 
during this process. Observe now the electrometer intensity n 
degrees at a given distance of the attracting discs p,m. Suppose 
the number of measures 5; distance of the plates a, ¢ *5 of an 
inch, distance of the attracting discs p, n *6 of an inch, and the 
index indication 10 degrees. 
Replace plate 4, and put it also in connexion with the 
ground. Discharge the air between ¢ and a by a communi- 
cation between the two coatings or plates a, c in the usual way, 
and repeat the former process; the number of measures now 
requisite to produce 10 degrees of force will be 10 measures, or 
just double the former. The plate c, therefore, or rather the 
air, has now charged in proportion to the two surfaces of the 
plate, which in this case have been each exposed to a free induct- 
ive action, and the electricity proper to the plate c has been en- 
abled to retire, as it were, outward toward the stratum of air on 
each side of it. 
24. This is precisely what happens in the case of what we term 
the charging simple insulated conductors, except that from the 
distance of other conducting matter taken as the opposite or un- 
insulated coating to the charge, the accumulation is less complete 
and more feeble. If we look at this question somewhat critically, 
we may probably be led to conclude that the essence of the charge 
is virtually the displaced electricity proper to the plate itself (9), 
(17). Suppose, for example, that we are about to communicate 
a given measure of electricity to the rectangular plate add, 
fig. 20, through the intervention of a small carrier-ball c, charged 
to saturation, suppose positively, and applied to any point ¢ of 
the plate. The first action will be that of direct and reflected 
induction, already explained (3), fig. 2; that is to say, the elec- 
tricity proper to the plate recedes in every direction, ca, cd, cb, 
from the point c, and a powerful negative space, c, is for a moment 
produced all around it; at the same instant, the charge, before 
distributed uniformly over the carrier-ball, concentrates itself by 
the reflected induction immediately upon the point ¢ in contact 
with the plate ; a neutralization of the opposite forces ensues, and 
the plate and surrounding air remain charged with the displaced 
electricity. If the magnitude of the plate be considerable in 
respect of the carrier-ball, all its charge, or nearly all, will have 
disappeared on a first contact ; and the charge communicated as 
in the Leyden jar will be so greatly masked by the inductive 
action of surrounding matter, that comparatively little effect is 
produced on an electrometer, n, placed in connexion with the 
plate. On a repetition of this operation, the same actions are 
apparent: another quantity of electricity becomes displaced, and 
again the carrier-ball becomes robbed of its electricity. The 
Phil. Mag. 8. 4. Vol. 14. No. 92. Sept. 1857. N 
