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HORNBLENDE SCHIST. beds of various dimensions, and under all the usual va riations. When intermixed with gneiss, which is its predominant association, for reasons already apparent, it follows the contortions of that rock; affording, by its contrast of colour, the most perfect indications of those; and, as already remarked, it is traversed hv the same granite veins. 11 ence, it has been called subor dinate ; but, as already said, this only proves that the intrusion of the veins was posterior to the deposition of the compound mass. Wherever, like the gneiss it self, it is unaffected by these veins, all that follows is, that no intrusion of granite has there taken place since its deposition, it is occasionally found among the greater masses of micaceous schist ; while hornblende then sometimes enters into the composition of that rock, so as to produce an intermediate substance. In these cases, other compound and anomalous strata are often present; chlorite schist being frequently among the number. Its peculiar association with this rock has just been described. It is occasionally found accompanying argillaceous schist; appearing to pass into the finer clay-slate by an insensible gradation. I have already shown the peculiar interest attached to this transition at the con tact with granite; particularly remarkable where its veins traverse clay-slate, or whese fragments of the latter are entangled in it. From tin's fact, and the pa rallel ones at the contact of shales and trap, it would appear, that the fusion of clay-slate, whether primary or secondary, is, under various circumstances, ca pable of generating, either the common trap rocks, or the hornblende schists : nor is it perhaps difficult to explain, by a more gradual cooling, and consequently, a slower crystallization, the particular causes which may have determined the latter rather than the former effect. Instructive examples of this transition occur