N 0 charge has yet been observed which is smaller than that on the electron. Every charge observed, which is sufficiently small to be directly compared with that of the electron, has been found to be an exact integral multiple of it. We are thus led to the conclusion that electricity is atomic in structure; the smallest possible unit of charge being that of the electron, which thus constitutes our fundamental unit of electricity. Moreover it can be shewn that the mass of the electron is entirely an electrical effect, and is due solely to the charge which it carries. The electron therefore constitutes a real atom of electricity.