Page:The evolution of worlds - Lowell.djvu/167

Rh etiquette with reference to the Sun. And it will be noticed that they stand to him the nearest of his court. Here, then, is a law of proximity which points conclusively to some well-established force.

Last is a remarkable congruity which study disclosed to me likewise some years ago, and which has received corroboration in discoveries since. This congruity is the peculiar arrangement of the masses in the solar system.

Consider first the way in which the several planets, as respects size, stand ordered in distance from the sun. Nearest to him is Mercury, the smallest of all the principal ones. Venus and the Earth follow, each larger than the last; then comes Mars, of distinctly less bulk, and so to the asteroids, of almost none. After this the mass rises again to its maximum in Jupiter, and then subsequently falls through Saturn to Uranus and Neptune. Here we mark a more or less regular gradation between mass and position, a curve in which there are two ups and downs, the outer swell being much the larger, though the inner, too, is sufficiently pronounced.

Now turn to Saturn and his family, which is the most numerous of the secondary systems and that having the greatest span. Under Saturn's wing, as it were, is the ring, itself a congeries of tiny satellites. Then comes Mimas, the smallest of the principal ones; then Enceladus, a little larger; then Tethys, the biggest