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From the shortness of our visit, I did not examine these beds with care; some of them, especially those of the white, yellow, and brown shades, originally existed as streams of lava, but the greater number were probably ejected in the form of scoriae and ashes: other beds of a purple tint, porphyritic with crystal- shaped patches of a white, soft substance, which are now unctuous, and yield, like wax, a polished streak to the nail, seem once to have existed as solid claystone-porphyries: the red argillaceous beds generally have a brecciated structure, and no doubt have been formed by the decomposition of scoriae.
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