APPENDIX
The breaking up of an atom of matter is by some thought to be of the nature of an explosion, the pieces being expelled with deflagrating violence; by others it is thought to be the tangential flying off of a part whenever it attains a certain critical velocity.
In any case there appears to be an enormous store of energy, both potential and kinetic, inside an atom; and when for any reason either of these energies rises above a certain value, disruption results. Explosion might be brought about by an accidental configuration in which the repulsive forces came prominently into play. Instability of motion would result if any charged particle attained to the speed of light, for in that case there are good theoretical and some experimental reasons for asserting that its momentum would disproportionately increase, without any counterbalancing increase in the retaining force. The mass of matter is usually assumed constant, and so it is at all ordinary speeds; but, according to the electrical theory of matter, the mass is not quite constant at high velocities, but increases slightly with the speed, until at the speed of light itself it becomes suddenly infinite. In any case the instability of an atom must be regarded as a natural consequence of the electrical theory of matter, and of the fact that an accelerated electric charge radiates its energy away. Consequently Professor Larmor some years ago expected radio-activity, and saw no reason why it should
