Page:Popular Science Monthly Volume 4.djvu/51

Rh other distances of the same class. Let it be noticed, then, that Saturn's mean distance from the sun exceeds the earth's more than nine and a half times. Now, Jupiter's distance exceeds the earth's rather more than five times (five and a fifth is very nearly the true proportion); so that between Jupiter's path and Saturn's there lies everywhere a span fully equal to four times the earth's distance from the sun. So much for Saturn's nearest neighbor on that side. But on the farthest side lies Uranus, more than nineteen times as far away from the sun as our earth is; so that between the paths of Saturn and Uranus there lies everywhere a span equal to Saturn's own distance from the sun. Now, all this is not intended as a mere display of wonderful distances. So far as mere dimensions are concerned, these arrays of figures are more imposing than impressive. But, so soon as we take into account the circumstance that a planet is in some sense ruler over the spaces through which its course carries it, those spaces being by no means tenantless, we see that, cæteris paribus, the dignity of a planet is enhanced by the extent of the space separating its orbit from the orbits of its neighbors on either side. Now, the space between the paths of Saturn and Jupiter exceeds the space inclosed by the earth's orbit no less than 63 times, while the space between the paths of Saturn and Uranus exceeds the space inclosed by the earth's orbit 270 times! Assuming (as we seem compelled to do by continually-growing evidence) that Saturn and his system were formed by the gathering in of matter from the region over which Saturn now bears sway, we cannot wonder that the planet is a giant, and his system wonderful in extent and complexity of structure. It is true that Jupiter on one side, and Uranus on the other, share Saturn's rule over the vast space, 330 times the whole space circled round by the earth, which lies between the orbits of his neighbor planets. But Saturn's rule is almost supreme over the greater part of that enormous space. Combining the vastness of the space with its position—not so near to the sun that solar influence can greatly interfere with Saturn's, nor so far away as to approach the relatively-barren outskirts of the solar system—we seem to find a sufficient explanation of Saturn's high position in the scheme of the planets as respects volume and mass, and his foremost position as respects the complexity of the system over which he bears sway.

Briefly, then, to indicate his proportions, and the dimensions of his system:

Saturn has a globe considerably flattened, his equatorial diameter being about 70,000 miles, while his polar axis is nearly 7,000 miles shorter. Thus in volume he exceeds the earth nearly 700 times, and all the four terrestrial planets––Mercury, Venus, the Earth, and Mars—taken together, more than 336 times. In mass he does not exceed the earth and these other smaller planets so enormously, because his density (regarding him as a whole) is much less than the earth's. In fact, his density is less than that of any other known body (comets,