Suppose the sun to be represented by a radiant little orb two feet in diameter, in order to bring it within the measure of our eye; then this great globe of ours, with all its stupendous histories, is no bigger than a full-sized pea in proportion, revolving at the distance of 215 feet. Neptune, the outermost and last discovered of the planets, would stand at the distance of a mile and a quarter from a sun of that imaginary size, and it would be no larger than a cherry. Another cherry at the distance of three-quarters of a mile would stand for Uranus. Saturn would be a small orange at two-fifths of a mile from our two-feet solar body. A middle-sized orange, at the distance of a quarter of a mile, would be his Jupiter. At some 500 feet the nine little planets, commonly called asteroids, probably enough the fragments of an exploded orb, and now moving in a sort of group, would be represented by as many grains of sand. A pin-head, at 327 feet, would do for Mars. Then comes the earth. Still nearer the sun, namely at 142 feet from our present model, revolves Venus, of the dimensions of a pea. And finally little Mercury wheels along his orbit, with a radius of 82 feet, and the dimensions of a mustard seed. Add the terrestrial moon, the four moons of Jupiter, the ring within ring that whirls round Saturn like an endless moon, the eight ordinary moons of that extraordinary planet, the moons of Uranus and Neptune (yet uncertain in their number), and it is impossible to say how many comets, not to forget the enormous groups or hosts of comparatively small stones or meteors, which are believed to be revolving round the solar centre like pigmy asteroids; and the Copernican conception of the mere constitution of the solar system, as developed by time and toil, is completed. The sun is 882,000 miles in diameter; the earth is 7926; Juno is 79; Saturn, 79,160, and so forth. The earth is more than five times as heavy as water; Saturn is as light as cork. The earth rotates in twenty-four hours; Jupiter in ten. The earth revolves in a year; Mars in a year and ten months; Mercury in about three months; Venus in seven and a half months; Jupiter in eleven years; Saturn in twenty-nine; Uranus in eighty-four; Neptune in a hundred and sixty-four. A summer in Mercury lasts some three weeks; in Neptune forty-one years. Light leaps from the sun to the earth in eight minutes; to Neptune in four hours. In short, the reader has to consider thousands of discovered facts, to carry with him a whole world of indubitable inference, and to study a truly wonderful bringing of the whole machinery, or rather organization, to geometrical law, before he can apprehend how glorious a whole the Copernican astronomy has become. THE CONVICT'S TALE.