88 Sir W. Snow Harris’s Researches in Statical Electricity. 
thing ; the difference is a difference of degree, not of kind; they 
are, in fact, both reducible to the elements of the electrical or 
. Leyden jar. Indeed, every case of what is commonly called a 
charged conductor, resolves itself into the form of a coated elec- 
tric, and is the result of a peculiar disposition and combination 
of electrics and conductors; it is, in fact, the accumulation of 
electricity upon the terminating strata of a dialectric medium 
bounded by, and in direct contact with, conducting matter, 
either near or distant. Thus, in the case of what has been 
termed a charged hollow metallic globe, in which all the charge 
is conceived to be impelled, as it were, by the repulsive force of 
its particles from a centre of force, and so find its way to the 
surface of the metal, we find on an attentive examination the 
following arrangement of conductors and electrics, fig. 8, and 
into which every case of electrical charge may be finally resolved. 
We have, first, a metallic surface P; secondly, exterior to this 
an insulating medium aA, viz. atmospheric air, in a stratum 
of which, a, immediately surrounding the globe, there is a dense 
electrical accumulation ; thirdly, beyond this stratum we have in 
continuation other air, A, not so immediately electrified, and sus- 
ceptible of further inductive change: the external air is in its 
turn bounded by other conducting matter, N. When, therefore, 
we impart free electricity to the hollow sphere P, we do nothing 
more than cause an electrical accumulation to ensue upon the 
stratum a, according to the well-established principles of the 
Leyden experiment. We do not, in fact, charge the sphere at 
all, any more than we charge the coating of an electrical jar: 
indeed it is doubtful if in any case we could charge a metallic 
conductor taken apart from, or in the absence of, a dialectric 
boundary. The globe itself can be regarded in no other light 
than that of the inner coating of a given dialectric bounded by 
distant conducting matter, and which we may consider as the 
opposed coating; the metal of the globe is merely the conductor 
to the charge. The inductive action upon which the charge de- 
pends, may be shown to extend to great distances. Cavendish 
traced it from the centre to the walls of a room 16 feet in dia- 
meter*. Faraday traced it from a ball suspended in the middle 
of a room to the walls, 26 feet distant}. 
If we examine the experiment of the charged glass globe (7), 
fig. 5, we find the elementary conditions precisely the same. 
Here we have (fig. 8) an interior coating of mercury P, then an 
external dialectric aA, which in this case is glass; finally, an 
outer coating of mercury N. Here, as in the preceding case, we 
do not charge the interior mercury, as is well known, although 
it may possibly, on being removed, be slightly electrified : the 
* Cavendish, MS. + Experimental Researches, 1303. 
