A wonderful feature of the infinitely tenuous ether is, that while its ultimate particles must be inconceivably more minute than the ultimate atoms of ordinary matter, the movements taking place in it are transmitted with enormous velocities. The structure of our universe is on a grander scale; its least atom may comprise millions of millions of the largest component portions of that infinitely tenuous ether. But amid that ether motions are transmitted with velocities transcending all but infinitely those which take place among the particles of matter composing the universe in which we "live and move and have our being." The planets, immense aggregates of matter such as we know it, sweep onwards upon their immense orbits, traversing many thousands of miles in an hour; but light and heat sweep along the ether of space, and by virtue of motions taking place within that ether at the rate of many tens of thousands of miles per second. The suns which people space rush onwards with mightier momentum, but less swiftly than the planets in their orbits. Comets attain the greatest velocities of all the bodies that science deals with, rushing sometimes, in their periastral swoop, with a velocity of hundreds of miles per second,--though yet in mid-space the comets of widest orbital range lag slowly enough, insomuch that some of those which, when nearest our sun, travel at the rate of two or three hundred miles per second, move more slowly when very far from him than many of our rivers. Taking even the swiftest rush of a comet within the solar domain, we find that light speeds along five hundred times more quickly,--so that if we represent the velocity of light by that of an express train (reducing light's velocity in scale to about one-10,000,000th part of its real value), the velocity of the most swiftly-moving comet would be represented by that of a walk at the rate of one-eighth of a mile per hour,--a very slow walk indeed.