radium is itself a product of the disintegration of some heavier element which has been undergoing this process of decay since the world began.
Subatomic Energies.
The energy which would be required to produce such changes from the simpler to the heavier atoms, and the equivalent energies which are set free when the heavier atoms disintegrate into simpler ones, are enormously greater than those involved in the changes which take place in the constitution of molecules in the ordinary chemical transformations with which we have thus far been familiar. The disintegration of a gram of uranium, or thorium, or radium, sets free at least a million times as much energy as that which is represented in any known chemical change taking place within a gram weight of any known compound substance. The experiments of the last eight years have then marked a remarkable advance in science in that they have proved the existence of an immense store of subatomic energy. It seems highly improbable, however, that this energy can ever be utilized on the earth to serve man's economic needs, for thus far we know of but three substances which are disengaging it and these are changing so slowly that the rate of evolution of energy is almost infinitesimal. Radium may possibly prove to be of some practical value in the cure of disease, although it is too early yet to assert even this with certainty. But even if no practical application of these discoveries should be found, radio-activity will nevertheless have served one of the most useful of all ends, namely, that of enlarging man's knowledge of the ways of nature and of deepening his insight into the constitution of matter.
