THE REIGN OF FIRE. 51 



and float upon the liquid portions. This apparent excep- 

 tion 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 refrigera- 

 tion 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 ac- 

 counting 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 jos- 

 tling 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 



