"so full," says Clerk Maxwell, "that no human power can remove it from the smallest portion of space, or produce the slightest flaw in its infinite continuity." The scientific imagination, in its attempts to master the workings of the material universe, has thus given us a creation which in many of its attributes rivals Omnipotence. It is the sum of all contradictions, and the source of all reality. The gross matter which we see and feel is one state of it; electricity, which is without form and void, is another state of it; and our minds and souls, Sir Oliver Lodge intimates, may be still another state of it. But all these theories of physical science are justified by their fruits. The atomic theory of matter, and the kinetic theory of gases, are mathematically demonstrated. However unreal and fantastic they may appear to our practical faculties, conversant only with ponderable bodies, they bear the test of the most rigid and exact experimentation. V After we have marveled over all these hidden things, and been impressed by the world within world of the material universe, do we get any nearer to the mystery of life? Can we see where the tremendous change from the non-living to the living takes place? Can we evoke life from the omnipotent ether, or see it arise in the whirling stream of atoms and electrons? Molecular science opens up to us a world where the infinitely little matches the infinitely great, where matter is dematerialized and answers to many of the conceptions of spirit; but does it bring us any nearer the origin of life? Is radio-active matter any nearer living matter than is the clod under foot? Are the darting electrons any more vital than the shooting-stars? Can a flash of radium emanations on a zinc-sulphide plate kindle the precious spark? It is probably just as possible to evoke vitality out of the clash of billiard-balls as out of the clash of atoms and electrons. This allusion to billiard-balls recalls to my mind a striking passage from Tyndall's famous Belfast Address which he puts in the mouth of Bishop Butler in his imaginary argument with Lucretius, and which shows how thoroughly Tyndall appreciated the difficulties of his own position in advocating the theory of the physico-chemical origin of life.