Homer’s world, restricted to less than a drummer’s circuit, was nevertheless immense, surrounded by a thin veneer of universe—­the Stream of Ocean.  But how it has shrunk!  To-day, precisely charted, weighed, and measured, a thousand times larger than the world of Homer, it is become a tiny speck, gyrating to immutable law through a universe the bounds of which have been pushed incalculably back.  The light of Algol shines upon it—­a light which travels at one hundred and ninety thousand miles per second, yet requires forty-seven years to reach its destination.  And the denizens of this puny ball have come to know that Algol possesses an invisible companion, three and a quarter millions of miles away, and that the twain move in their respective orbits at rates of fifty-five and twenty-six miles per second.  They also know that beyond it are great chasms of space, innumerable worlds, and vast star systems.

While much of the shrinkage to which the planet has been subjected is due to the increased knowledge of mathematics and physics, an equal, if not greater, portion may be ascribed to the perfection of the means of locomotion and communication.  The enlargement of stellar space, demonstrating with stunning force the insignificance of the earth, has been negative in its effect; but the quickening of travel and intercourse, by making the earth’s parts accessible and knitting them together, has been positive.

The advantage of the animal over the vegetable kingdom is obvious.  The cabbage, should its environment tend to become worse, must live it out, or die; the rabbit may move on in quest of a better.  But, after all, the swift-footed creatures are circumscribed in their wanderings.  The first large river almost inevitably bars their way, and certainly the first salt sea becomes an impassable obstacle.  Better locomotion may be classed as one of the prime aims of the old natural selection; for in that primordial day the race was to the swift as surely as the battle to the strong.  But man, already pre-eminent in the common domain because of other faculties, was not content with the one form of locomotion afforded by his lower limbs.  He swam in the sea, and, still better, becoming aware of the buoyant virtues of wood, learned to navigate its surface.  Likewise, from among the land animals he chose the more likely to bear him and his burdens.  The next step was the domestication of these useful aids.  Here, in its organic significance, natural selection ceased to concern itself with locomotion.  Man had displayed his impatience at her tedious methods and his own superiority in the hastening of affairs.  Thenceforth he must depend upon himself, and faster-swimming or faster-running men ceased to be bred.  The one, half-amphibian, breasting the water with muscular arms, could not hope to overtake or escape an enemy who propelled a fire-hollowed tree trunk by means of a wooden paddle; nor could the other, trusting to his own nimbleness, compete with a foe who careered wildly across the plain on the back of a half-broken stallion.