§ =96.= It has been pointed out, however, that (in a sense) this change (viz., of emanation into helium) is not quite what has been meant by the expression “transmutation of the elements”; for the reason that it is a _spontaneous_ change; no effort of ours can bring it about or cause it to cease.[114] But the fact of the change does go to prove that the chemical elements are not the discrete units of matter that they were supposed to be. And since it appears that all matter is radioactive, although (save in these exceptional cases) in a very slight degree,[115] we here have evidence of a process of evolution at work among the chemical elements. The chemical elements are not permanent; they are all undergoing change; and the common elements merely mark those points where the rate of the evolutionary process is at its slowest. (See also §§ 78 and 83.) Thus, the essential truth in the old alchemistic doctrine of the growth of metals is vindicated, for the metals do grow in the womb of Nature, although the process may be far slower than appears to have been imagined by certain of the alchemists,[116] and although gold may not be the end product. As writes Professor Sir W. Tilden: “. . . It appears that modern ideas as to the genesis of the elements, and hence of all matter, stand in strong contrast with those which chiefly prevailed among experimental philosophers from the time of Newton, and seem to reflect in an altered form the speculative views of the ancients.” “. . . It seems probable,” he adds, “that the chemical elements, and hence all material substances of which the earth, the sea, the air, and the host of heavenly bodies are all composed, resulted from a change, corresponding to condensation, in something of which we have no direct and intimate knowledge. Some have imagined this primal essence of all things to be identical with the ether of space. As yet we know nothing with certainty, but it is thought that by means of the spectroscope some stages of the operation may be seen in progress in the nebulæ and stars. . . .”[117] We have next to consider whether there is any experimental evidence showing it to be possible (using the phraseology of the alchemists) for man to assist in Nature’s work. [114] See Professor H. C. JONES: _The Electrical Nature of Matter and Radioactivity_ (1906), pp. 125-126. [115] It has been definitely proved, for example, that the common element potassium is radioactive, though very feebly so (it emits β-rays). It is also interesting to note that many common substances emit corpuscles at high temperatures. [116] Says Peter Bonus, however, “. . . we know that the generation of metals occupies thousands of years . . . in Nature’s workshop. . . .” (see _The New Pearl of Great Price_, Mr. A. E. Waite’s translation, p. 55), and certain others of the alchemists expressed a similar view.