638. The silicious formation returning in the stratified periods is chiefly under the condition of _sandstone_. Apart from that, which has originated through the detritus of the older kinds of rocks, it may be assumed, that the prevailing lime still held some silicious earth in a state of moisture within itself, and that this during its separation was precipitated as a fine alcohol, namely, as sand. If, however, sand fell, so also must a proportionate quantity of lime fall, by combining itself with an acid. Sand and lime therefore usually accompany each other. If the two be regarded also as only floated freely and suspended in water, still the chemical antagonism manifests itself between them as if they were in a mortar, and they have been precipitated in layers alternating with each other. The sandstone is as a rule therefore imbedded in the lime; it is a mortar containing but little lime. The mechanical silicious deposits are exemplified in the Nagelfluh, old red sandstone, Grauwacke, sandstone and drift-sand. 639. The stratified clay appears to have been deposited as clay-stone; it passes over into slate and potters' clay. The talcose strata pass by serpentine and potters' stone into steatite and meerschaum. STRATIFIED LIMESTONE. 640. The pole which had operated continuously from the fundamental earths contained in the Earthy has now separated from it, and the tension is again extinguished. The Earthy is now contained in a pure state in water without continuance of the silicious pole; the influx of water has now obtained the preponderance. So soon, however, as the antagonism of this water to the stratified silex, clay and talc ceases, the more internal, hitherto restrained by the feebler antagonism, becomes awakened, as it did after the precipitation of the fundamental earths. 641. The principles are necessarily combined more firmly in the fundamental than in the calcareous earths. In this both the oxygenic and basic earth-principle must each attain for itself completion, and represent the two primary bodies in the earth with the same capacity for separation and activity. 642. The production of earths results from a constant antagonism subsisting between them and water. The more the Basic is thrown down, by so much does the Oxygenous preponderate to a greater degree in water. The water becomes oxydized and seeks to divide into its two principles, into oxygen and hydrogen. 643. By this contest tension is also excited in the earth-principles, namely, oxygen and carbon, and they begin in themselves to separate. The metallic basis of the earths strives to become free. During the separation, however, the oxygen snatches as it were some carbon along with it and appears as carbonic acid; but the carbon of the earthy lays claim to some of the hydrogen and oxygen to combine with it and appears as corrosive or calcareous earth.