Passing on evolutionarily we reach more and more tolerable conditions and solid ground in fact, as well as theory. Thus the crust hardened and cooled, while the oceans still remained uncomfortably hot. For water requires much more heat to warm it to a given temperature than rock, about four and a half times as much. It has therefore by so much the more to lose, and is proportionally long in the losing. These hot seas must have produced a small universe of cloud, and as the conditions were the same all over the Earth, we can see easily with the mind’s eye that we could not have seen at all with the bodily one, had we occupied the land in those very early days. To be quite shut out from curious sight without, was hardly made up for by not being able to see more than dimly within. Any one who has stood on the edge of a not-extinct crater when the wind was blowing his way, will have as good a realization of the then state of things as he probably cares for. Now this astronomic drawing of the then Earth, which by its lack of detail allows of no doubt whatever, permits us to offer help in the elucidation of some of their phenomena to our geologic colleagues. We are the more emboldened to do so in that they have themselves appealed to astronomy for diagnosis, and accepted nostrums devised by themselves. It is always better in such cases to call in a regular practitioner. Not that he is necessarily more astute, but that he knows what will not work. It was in the matter of the paleologic climate that they were led to consult astronomy. The singular thing about paleologic times was the combination of much warmth with little light; and the not less singular fact that these conditions were roughly uniform over the whole Earth. From this universality it was clear, as De Lapparent, their chief spokesman, puts it, that nothing local could explain the fact. It was something which demanded a cause common to the globe. It thus fell properly within the province of astronomy. For if we are to draw any line between the spheres of influence of the two sciences, it would seem to lie where totality ends and provincialism begins. I use this not as a pejorative, but simply to part local color from one universal drab. In the Earth’s general attributes,—its size, shape, and weight,—we must have recourse to astronomy to learn the facts. Not less so for those principal causes which have shaped its general career; we surrender it only at the point where everyday interest begins, when those causes that led it through its uninviting youth give way to effects which in the least concern humanity at large.