Sir W. Snow Harris’s Researches in Statical Electricity. 95 
proof-plane applied to these surfaces in the usual way might 
actually evince a greater reactive force when applied to the rect- 
angle, although the surface and quantity of electricity were actu- 
ally the same as in the square or circular plate; the electrical 
stratum on the rectangle being less condensed, as it were, upon 
any given point of its surface. Now a touching body, prepared 
as in fig. 11, so as to be susceptible of a free induction, will, 
when transferred to the balance, at once show the difference of 
intensity in the two surfaces, and although not in this case 
affording a correct measure of the relative quantity of electricity, 
may under another form of the experiment be made available for 
that purpose. 
17. It is to be here considered how far the presence of a cy- 
lindrical conductor ap, fig. 10, elevated above the charged plane, 
_is calculated to disturb the original distribution, and change its 
quantitative condition upon different points of the surface. That 
a portion of the electrical accumulation becomes transferred to 
the cylinder is certain; but the quantity is not in proportion to 
its extent of surface, or such as to interfere in any appreciable 
degree with the original distribution, which will be found to 
remain precisely the same whether the cylinder ap, fig. 10, be 
present or not. The cylinder, in fact, may be considered to 
become charged in great degree by a new distribution of its own 
electricity, and to become affected in pretty much the same way 
as the carrier-ball and wire introduced into the hollow sphere 
(9), Exp. 6, fig. 7, that is to say, a portion of the electricity of 
the cylinder itself, in the face next the charged surface, first 
becomes displaced by induction (8), fig. 2, and retires towards 
its remote or distant face p, fig. 10. This preparatory change 
complete, the near or lower face of the cylinder then receives or 
shares in the total charge in proportion to the amount of this 
induction ; so that a new quantity of electricity proper to the 
cylinder itself is thus called into action and becomes sensible at 
its remote portions, and the quantity of charge taken by the 
cylinder is limited in extent to the element of the surface it 
actually covers. Now the influence of this upon the general and ° 
original state of the distribution is quite mappreciable, as may 
be easily shown by taking the reactive force at any given point 
with and without the presence of the cylinder, when the force 
will be found precisely the same. 
The method, then, of determining the reactive force generally 
of the charged plate P, or of any point of it, through the medium 
of an intervening elevated conductor of a given form and dimen- 
sions, appears to be the best and most accurate process which can 
be possibly employed, inasmuch as the electrical development at 
its distant face p, fig. 10, will always be in the direct proportion 
