In fine, to make us realize not merely how extremely narrow are the bounds of our knowledge, but even how much narrower they may be than we suppose, there enters upon the scene Radium, like the golden apple that came to disturb the harmony of the celestials. What lessons this turbulent and unconventional element will ultimately be found to teach, and how far it will revolutionize the laws of Nature as hitherto accepted, remains, of course, to be seen: but this at least is clear. In presence of it, scientific men find that they are sure of nothing they thought most certain, not of the indestructibility of matter itself, on which is based that Law of Substance which we have seen made responsible for so much. It had been thought that whatever else might change or perish the atoms of which we have heard, as the ultimate constituents of Matter, were beyond the reach of any vicissitude. "No man," said Dalton, their discoverer, "can split an atom." Thus too Mr. Clodd, while acknowledging that the constitution even of atoms may some day be found to be liable to disorder and decay, clearly teaches that, as a practical certainty, we have in them got to something final. Taking one particular kind, an oxygen atom, as a text, he thus discourses:[58] It matters not into how many myriad substances--animal, plant, or mineral--an atom of oxygen may have entered, nor what isolation it has undergone: bond or free, it retains its own qualities. It matters not how many millions of years have elapsed during these changes, age cannot wither or weaken it; amidst all the fierce play of the mighty agencies to which it has been subjected it remains unbroken and unworn; to it we may apply the ancient words, "the things which are not seen are eternal." But now, with the recognition of radio-activity, and the disintegration of atoms into their constituent "electrons" which this is held to evidence, we have changed all that. Such disintegration, it is affirmed, must imply dissolution and death, alike of the atoms themselves and of the universe which they compose. As Sir William Crookes told the physicists assembled at Berlin, June, 1903: This fatal quality of atomic dissociation appears to be universal, and operates whenever we brush a piece of glass with silk; it works in the sunshine and raindrops, in lightnings and flame; it prevails in the waterfall and the stormy sea. Matter he consequently regards as doomed to destruction.[59] Sooner or later, it will have dissolved into the "formless mist" of "prothyle"[60] and "the hour-hand of eternity will have completed one revolution." Consequently, we are told,[61] The "dissipation of energy" has found its correlative in the "dissolution of matter." We are confronted with an appalling sense of desolation--of quasi-annihilation.