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Updated: May 6, 2025
Near Monte Video, where the stratification, as it would be called, of the metamorphic series is, in most parts, particularly well developed, being as usual, parallel to the foliation, we have seen that a mass of chloritic schist, netted with quartz-veins, is entangled in gneiss, in such a manner as to show that it had certainly originated in some process of segregation: again, in another spot, the gneiss tended to pass into hornblendic schist by alternating with layers of quartz; but these layers of quartz almost certainly had never been separately deposited, for they were absolutely continuous with the numerous intersecting veins of quartz.
Two or three hours' railway travel through vertical cuttings in metamorphic rock, through oak copses rich and green, stretching over slopes and down delightful valleys, glens, and ravines, sparkling with water like many-rilled Ida, and he plunged amid the hundred and fifty thousand people composing the town of Plymouth.
Tertiary strata, such as here described, appear to extend along the whole coast between Rio Chupat and Port Desire, except where interrupted by the underlying claystone porphyry, and by some metamorphic rocks; these hard rocks, I may add, are found at intervals over a space of about five degrees of latitude, from Point Union to a point between Port S. Julian and S. Cruz, and will be described in the ensuing chapter.
From this point the canyon bed and lower walls are granite, but the highest peaks are still a dark, splintery, metamorphic slate. The glacial erosion has here cut through the slate and bitten deep into the underlying granite.
The valley, deepening and narrowing, became a gorge, the beginning of that long series of fissures in the metamorphic and secondary rocks which, crossing an extensive tract of Languedoc and Guyenne, leads the traveller up to the Cevennes Mountains, through scenery as wild and beautiful as any that can be found in France, and perhaps in Europe.
Foliation may be used for those alternating layers or plates of different mineralogical nature of which gneiss and other metamorphic schists are composed. That the planes of foliation of the crystalline schists in Norway accord very generally with those of original stratification is a conclusion long since espoused by Keilhau. In Scotland, also, Mr.
Tierra del Fuego, clay-slate formation, cretaceous fossils of; cleavage and foliation; form of land. Chonos Archipelago, mica-schists, foliation disturbed by granitic axis; dikes. Chiloe. Concepcion, dikes, successive formation of. Central and Northern Chile. Concluding remarks on cleavage and foliation. Their close analogy and similar origin. Stratification of metamorphic schists.
Curiously enough he imagined fire to possess a solidifying power, and therefore attributed to it the solidity of the earth and the hardness of the rocks. No doubt he had observed some effects of fire in 'metamorphic' formations in his own vicinity.
It is not true, as was formerly supposed, that all granites, together with the crystalline or metamorphic strata, were first formed, and therefore entitled to be called "primitive," and that the aqueous and volcanic rocks were afterwards superimposed, and should, therefore, rank as secondary in the order of time.
This is now generally believed to have been the case with the Silurian, Devonian, Carboniferous, Oolitic, and Cretaceous limestones and those nummulitic rocks of tertiary date which bear the closest affinity to the Eozoon reefs of the Lower Laurentian. It has a strike from north-west to south-east, nearly at right angles to the metamorphic strata of the Grampians.
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