Page:The evolution of worlds - Lowell.djvu/180

148 and Venus to the Sun; and, thirdly, that the orbits of the satellites of all the planets are themselves tilted in accordance with what it would require.$7$

After the axial spins have been made over to the same sense, the second consequence of tidal action in the case of two bodies revolving about their common centre of gravity is to slow down both spins until first the smaller and then the larger turn the same face to each other and remain thus constant ever after. Now such is precisely the pass to which we observe the satellites of the planets have come. All that we can be sure of now turn the same face always to their primary. The Moon was the first to betray her attitude, because the one we can best note. On scrutiny, however, Jupiter's satellites, so far as we can make out, do the like; and Saturn's, too. And a very proper attitude it is, this regard paid to compelling attraction. Thus one of the congruities we noticed stands accounted for. The satellites could hardly have been at first so observant; time has brought about this unfailing recognition of their lords.

Of the peculiar massing of the bodies in the family of the Sun, and the still stranger copying of it in their own domestic circles, little can as yet be said in interpretation. That the planetary families and their ancestral group should agree is not the least strange part of the affair. It shows that none of them was fortuitous,