[…] So far, knowledge is confined to the one case of natural transmutation, that of the heavier elements into ones of lesser atomic weight with evolution of energy. It seems natural to assume that the elements of greater atomic weight possess, generally, greater intrinsic internal energy than lighter ones. If this be so, the transmutation of silver into gold would be, in all probability, a ruinous process. It is probable that, if ever transmutation becomes practically possible, the material products of the process will be of little more account than the products of combustion of the furnaces of the industrial world to day. With energy at its present value, no known elementary substance, probably, is so valuable that it could be built up with profit from elements of less atomic weight, owing to the enormous expenditure of energy required, or that could not be disintegrated into lighter forms, were this possible, for the sake of the energy that would be obtained. [...]