624. All the Earthy could not have been separated from the water by the first storm of precipitation. For the water now rested very much collapsed upon the earth's nucleus, and could no longer therefore assume the form of rain. That therefore which was now precipitated could no longer be thoroughly crystallized, but must follow the current and disquietude of the water, and thus emerge from it in a slaty or massive condition.
625. The quartz of the granite endeavours to set itself free from the clay and talc, or it becomes freed by the latter removing from it in virtue of its polar behaviour. There is therefore one series of rocks, in which the granite is constantly rejecting the feldspar and mica more and more, and at last subsists as quartz simply, which _quartzose rocks_ as forming entire mountains are for intelligible reasons not of frequent occurrence.
626. The completion of the gneiss in its entire separation from the granite, and the evolution of feldspar upon a large scale constitutes the _clay-slate_, and finally clay-stone and clay-porphyry. This yields us a new series of formations, in which the gneiss gradually attains to being divested of quartz and mica and to a pure position as feldspar. The clay-slate is a true gneiss, that has lost the definite particles of quartz and mica.
627. The position of mica-schist constitutes in its purity the talc-formation, talc-slate, chlorite-slate, hornblende-slate.
628. After these several precipitations, the calcareous mass remains behind in the water, and now, as in the first periods of crystallization, is charged with carbonic acid, and is precipitated as transitionary calx under the form of _mountain limestone_.
629. These formations are found upon the whole to be arranged on the earth, in the order of time at which they were precipitated from the water. In the middle of the loftiest mountains is granite, then gneiss and mica-schist; then follow quartzose rocks, clay-slate or porphyry, talcose rocks, and lastly on the edge of all these runs the chain of alpine or mountain limestone. In the last of these formations are found fossil remains of corals and molluscous animals. For these formations fell first of all after the water had a solid bottom, and the granitic mountains projected above it.