Page:A hundred years hence - the expectations of an optimist (IA hundredyearshenc00russrich).pdf/120

 ultimate physical structure of the universe. Such conjectures might be followed indefinitely in several directions, and the resulting conclusions would be more likely to err by timidity than by extravagance: but as there is no knowledge at present available which could serve as a guide to the probably-right, and as a warning against the probably-wrong, directions, it would be neither interesting nor useful to pursue them. Radium "the revealer," as Dr Saleeby has called it in one of those brilliant papers which fine imagination and delicate fancy have adorned with many another noble phrase and memorable image, opens the door to a whole world of new possibilities. Our whole conception of cosmic processes may have to be remodelled, in the light of those tiny scintillations which the spinthariscope has popularised. Already our notions concerning the nature of matter have been revolutionised. We are told that atoms, regarded hitherto as the ultimate units of matter—so small that Lord Kelvin has calculated that if a drop of water were magnified to the size of the earth the atoms in it would be somewhere between the size of small shot and the size of cricket balls—are themselves made up of a stuff so almost infinitely more tenuous, that the particles of it within the atom are, relatively to their size, farther apart than the planets of the solar system. Nor is