Again, since the pith ball, when charged with the electricity from glass, was attracted to the electrified sealing-wax, we conclude that bodies charged with unlike electricities attract one another. The electricity from glass is sometimes called vitreous, and that from sealing-wax resinous, electricity, but more frequently the. former is known as positive, and the latter as negative, electricity—it being understood that these words do not imply the possession of a positive nature by the one influence, or of a negative nature by the other, but are merely terms employed to express the apparent antagonism which exists between the two kinds of electricity.
82. The next point worthy of notice is that whenever one electricity is produced, just as much is produced of an opposite description. Thus, in the case of glass excited by silk, we have positive electricity developed upon the glass, while we have also negative electricity developed upon the silk to precisely the same extent. And, again, when sealing-wax is rubbed with flannel, we have negative electricity developed upon the sealing-wax, and just as much positive upon the flannel.
83. These facts have given rise to a theory of electricity, or at least to a method of regarding it, which, if not absolutely correct, seems yet to unite together the various phenomena. According to this hypothesis, a neutral, unexcited body is supposed to contain a store of the two electricities combined together, so that whenever such a body is excited, a separation is produced
