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XIV OF THE OBJECTS OF MINERALOGY. posed of crystals deposited in a confused manner, as in granite; or of crystals imbedded in some other substance, as in porphyry. These crystalline rocks contain no organic remains; and, as they are always found beneath, never above, those which do contain them, they are considered to have been of earlier for mation, and therefore have been termed Primitive rocks. Other mountain rocks have no appearance of crystallization ; but, on the contrary, seem rather to have been formed by the mere falling down, or settlement, of the substances of which they are composed, from the solution which contained them. These are always found above, never beneath, the crystalline rocks; and often include abundance of organic remains, both animal and vegetable. The more ancient of these, or such as contain the remains of animals of which the genera and species are extinct, are called Transition rocks; the more recent, or such as contain the remains of animals most nearly resem bling those now inhabiting our oceans, are called Flwtz or Flat rocks, because their position is considerably or perfectly horizontal; the former have received the name of transition, as connecting the primitive with the flcetz rocks. 15y most geo logists the transition and the floetz are classed together under the name of Secondary rocks. Primitive and secondary rocks have suffered considerable change and ruin from causes which it is not our present object to notice ; and their disintegrated portions, having beer, formed anew, now constitute that peculiar description of deposit which is termed alluvial, or diluvial, and which therefore consists of the debris of rocks. Such are some clays, gravel, sand, &c. and these often contain the remains of land and amphibious animals, and of fish ; they are found above the preceding, or sometimes rest ing immediately upon primitive rocks. But there is still another and a very different kind of rock, abundantly found in certain countries, which may in great mea sure be considered, like the preceding, as resulting from the ruin of rocks, but from an opposite cause, or by an agent di rectly the reverse, viz. by fire ; constituting those known by the name of Volcanic rocks. Many of these strongly bear the marks of heat, and even of fusion ; some, on the contrary, oiler no evi dence of their having been subjected to heat. Lofty mountains composed of primitive rocks usually present rugged and uneven summits, and steep acclivities on the sides, as though they had suffered by convulsion. 8uch as are wholly or externally composed of secondary beds or strata are less rugged, their summits are flattish or somewhat rounded, and their sides present acclivities more easily accessible. Both primitive and secondary mountains, more particularly the former, are traversed in various directions by fissures of