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.

The atomic and electronic theory of matter admits one to a world that does indeed seem unreal and fantastic.  “If my bark sinks,” says the poet, “’t is to another sea.”  If the mind breaks through what we call gross matter, and explores its interior, it finds itself indeed in a vast under or hidden world—­a world almost as much a creation of the imagination as that visited by Alice in Wonderland, except that the existence of this world is capable of demonstration.  It is a world of the infinitely little which science interprets in terms of the infinitely large.  Sir Oliver Lodge sees the molecular spaces that separate the particles of any material body relatively like the interstellar spaces that separate the heavenly bodies.  Just as all the so-called solid matter revealed by our astronomy is almost infinitesimal compared with the space through which it is distributed, so the electrons which compose the matter with which we deal are comparable to the bodies of the solar system moving in vast spaces.  It is indeed a fantastic world where science conceives of bodies a thousand times smaller than the hydrogen atom—­the smallest body known to science; where it conceives of vibrations in the ether millions of millions times a second; where we are bombarded by a shower of corpuscles from a burning candle, or a gas-jet, or a red-hot iron surface, moving at the speed of one hundred thousand miles a second!  But this almost omnipotent ether has, after all, some of the limitations of the finite.  It takes time to transmit the waves of light from the sun and the stars.  This measurable speed, says Sir Oliver Lodge, gives the ether away, and shows its finite character.

It seems as if the theory of the ether must be true, because it fits in so well with the enigmatic, contradictory, incomprehensible character of the universe as revealed to our minds.  We can affirm and deny almost anything of the ether—­that it is immaterial, and yet the source of all material; that it is absolutely motionless, yet the cause of all motion; that it is the densest body in nature, and yet the most rarified; that it is everywhere, but defies detection; that it is as undiscoverable as the Infinite itself; that our physics cannot prove it, though they cannot get along without it.  The ether inside a mass of iron or of lead is just as dense as the ether outside of it—­which means that it is not dense at all, in our ordinary use of the term.