of the energy of the observed radiation—large though that is—for something like 30,000 years.
15. It does not follow that the life of a piece of radium is as great as that; the data are uncertain at present, but there is absolutely no ground for the popular and gratuitous surmise that it emits energy without loss or waste of any kind, and that it is competent to go on for ever. The idea, at one time irresponsibly mooted, that it contradicted the principle of the conservation of energy, and was troubling Physicists with the idea that they must overhaul their theories—a thing which they ought always to be delighted to do on good evidence—this idea was a gratuitous absurdity and never had the slightest foundation; but the notion that radium was perhaps able to draw upon some unknown source or store of energy, without itself suffering loss, was a possibility which has not yet wholly disappeared from some minds. Sir W. Crookes, for instance, suggested that it might somehow utilize the most quickly moving atoms of air, after the fashion of a Maxwell demon—a possibility that should always be borne in mind as a conceivable explanation of the power of some living organisms. It is much more reasonable to suppose, however, that radium and the other like substances are drawing upon their own stores of internal atomic energy, and thereby gradually disintegrating and falling into other, and ultimately into more stable, forms of matter.
Not that it is to be supposed that even these are finally and absolutely stable: these too are subject to radiation loss, and so must be liable to decay; but
