THE POPULAR SCIENCE MONTHLY.
sion of the evidence already collected, or even a bare outline of it, would lead us far beyond the limits of this article, which is simply designed to show how much food for study even a feather will supply, and what broad questions it will lead us into.
|WHAT THE CHEMISTRY OF THE ROCKS TEACHES.|
IT is a general rule that substances can crystallize only while solidifying from the liquid state of either fusion or solution. The only exceptions are, that some few substances crystallize directly from their vapors without passing through the intermediate liquid form. Now, the older unstratified rocks of the geological formations, as the granites, are unquestionably fusible, are crystalline in their structure, and are practically insoluble. Therefore the evidence is conclusive that they were all at one time in a molten, fluid state.
Thus far, it would appear, geologists are agreed, since they have named these formations the igneous rocks. But, whether the melted minerals were ever heated to a higher degree than fusion—that is, to the condition of vaporized elements––is an inquiry either carefully avoided by the authorities in geology, or merely mentioned as pertaining to an ingenious hypothesis which, it is claimed, is unsustained by any sufficient proof. It remains to be seen, however, if this theory of the original gaseous form of the material elements does not follow as a necessary consequence from the chemical constitution of the rocks themselves; and if it does not explain and bear testimony in geological and cosmical sciences to such an extent as to make it absolutely essential to them.
The question here presented resolves itself into two alternatives: Either the materials of the earth's crust were formed, according to chemical laws, out of the simple elements preëxisting in liquid or gaseous form, or they were created in the condition of melted and oxidized masses ready to cool into granite and limestone. The latter supposition will hardly be seriously entertained in these days of free inquiry into the natural causes of things. It is now not only conceded, but expected, that science shall have sole jurisdiction in every case where compound bodies are the subject of investigation. To follow them back to the primal laws and elements of their being—to reveal the cause and manner of their birth among the atoms—is now the highest aim of inductive research. On this borderline of inquiry, where the known shades off into the unknown, and the finite into the infinite, science has of late gained its most signal triumphs. And it scarcely requires a prophetic sense to discern that the groundwork of