and float upon the liquid portions. This apparent exception to the law of expansion by heat is accounted for by supposing that, when the molecules of a solidifying fluid arrange themselves in a regular crystalline manner, they inclose certain minute spaces, so that the resulting crystal is a little more bulky than the unarranged molecules from which it was constructed. And this may be the case, even though a cooler temperature has caused them to shrink into closer proximity (for they are never in contact) than before crystallization. If this law applies to the refrigeration of water, type-metal, iron, and other substances, we may reasonably infer it to be a general law of matter. We should expect, then, that crystals of quartz would float upon molten quartz, or solid trap upon molten trap, just as solid iron floats upon molten iron, or solid ice upon molten ice. We have, therefore, not only evidences of the fact of a forming crust, but also a probable means of accounting for it.

We may conclude, then, that a solid film began to form over the surface of the molten sea. But the earth was even then, as from the beginning, obedient to the law of axial rotation; and the sun and moon reached forth, with their attractive influences, to solicit the mobile rocks into tidal elevations. As the wave pursued the moon around the earth, it daily ruptured the forming film, and only a wilderness of floating fragments remained, strewn over the surface of the fiery abyss. In due time, however-let us be liberal in our concessions of time-the rocking and jostling fragments became permanently frozen together, as the broken ice of Arctic seas, after being worried by winds and currents, seizes an interval of calm to consolidate into a vast and rugged floe. So the rock-floe of this fiery ocean formed, at length, a bridge of rough and sturdy strength. It was a mixed conglomerate of crystalline fragments, such

cools into a cloud of visible mist. An intelligence located upon our earth at this epoch would have seen the dusky atmosphere begin to thicken. In the far-off regions, wisps of vapor crept along the sky, as cirrhi in our day foretoken the gathering storm. They grew, and thickened, and darkened till a pall of impending clouds enwrapped the earth, and the light of sun, and moon, and star was shut out for a geological age.

Particle drew particle to itself, and rain-drops began to precipitate themselves through the lower strata of the fervid atmosphere. In their descent they were scorched to evaporation, as the meteor's light vanishes in mid-heaven. The vapors, hurrying back to the bosom of the cloud, were again sent forth, again to be consumed. At length they reached the fervid crust, but only to be exploded into vapor and driven back to the overburdened cloud, which had an ocean to transfer to the earth. The clouds poured the ocean continually forth, and the seething crust continually rejected the offering. The field between the cloud and the earth was one stupendous scene of ebullition.*

But the descent of rains and the ascent of vapors disturbed the electricities of the elements. In the midst of this cosmical contest between fire and water, the voices of heaven's artillery were heard. Lightnings darted through the Cimmerian gloom, and world-convulsing thunders echoed through the universe.

"The sky is changed! and such a change! Oh, night,

And storm and darkness!"

*Those who are acquainted with Figuier's interesting works will note a remarkable correspondence between his treatment of this subject and my own. It is but justice, therefore, to state that these chapters were drawn up long before the work of Figuier appeared. This, indeed, has been my conception of these primeval scenes since 1856; and it was in print in 1857.