"The theory that the atoms of matter are all built up of some simple fundamental unit or protyle has been advanced at various times by prominent chemists and physicists. One of the earliest hypotheses of this kind was that due to Prout, who supposed that all the elements were built up of hydrogen. This general point of view has received strong support from observations that the properties of elements vary in a periodic manner with their atomic weight. This is exemplified by the classification of the elements according to the well-known periodic law. In order to explain the electrical and optical properties of matter, it was generally supposed that the atom consisted of a number of positively and negatively charged particles, held in equilibrium by electrical forces. The properties of such electrical atoms were early studied by Larmor and Lorentz."