not occur in every form of matter; and recently the researches of the Hon. R. Strutt seem to make it probable that most materials actually have some extremely slight radio-active power. It is a power which, as we have endeavoured to show, must be regarded not as the property of any fixed and permanent substance, but as the concomitant and advertisement of catastrophic change from one form of matter into another.
The phenomenon bears a sort of crude resemblance to an astronomical case: namely, the contraction and gradual collapsing of a nebula, with occasional shrinking off of peripheral material as an unstable stage is periodically reached, in accordance with the rough approximation known as Bode's law; together with a strong radio-activity of the central mass, and the conversion of constitutional potential energy into heat.
