Page:The Solar System - Six Lectures - Lowell.djvu/115



The same is the case with Saturn. Stanley Williams, in 1893, found for the Saturnian regions between 6° N. and 2° S., 10h13m, and for those between 17° N. and 27° N., 10h15m. Not only did latitudes differ in rate, but different longitudes went each at its own pace.

Something similar is true of the Sun. At the Sun's solar equator the spin is swifter than on either side of it; and the rate decreases steadily from the equator towards the poles. Spots near the equator go round in 25 days (25.23 days), spots in latitude 30° in 26½ days, in latitude 40°, 27 days, while in latitude 45° they take fully two days longer than in 0°. Now Willsing and Professor Sampson, of Durham University, have shown that such a state of things should result in the process of condensing from nebula to star. In the nebula, if the density varied from place to place, which, on the doctrine of chances, would certainly be the case, the several parts would revolve round their common centre of gravity at various rates. As the nebula condensed, such parts as held together would tend to equalize their individual motions through friction, until a common rotation was brought about. But this would consume a long time; in the mean while, the equatorial parts would outstrip the others. In the midst of the