Volltext Seite (XML)
f)0 CHAP. VI. On the general Distribution of the Materials which constitute the Earth. The superficial parts of the earth, which are all to which we can have access, whether by observation or inference, are formed of indurated and of loose ma terials; the first constituting rocks, and the latter being the various alluvial substances which, no less than the former, are objects of geological investigation. In the following chapters, thevarious details,whether of a general or of a particular nature, namely, those which relate to the substances themselves, and those which have a reference to the constitution of the globe, the origin of these materials, and the various revolutions they have undergone, will be considered in the several points of view which may appear necessary. The object of the present is to give a sketch of the most remarkable distinctions among rocks, and of their general distri bution as constituent parts of the earth. Observation has shown that rocks may be divided into unstratified and stratified: or into those, of which the forms arc irregular, and those which are disposed in successive beds, maintaining a general parallelism, for, at least, certain spaces. To these must be added, veins, which intersect all rocks; and those repositories of earthy and metallic minerals in a mixed or confused state, which occupy similar situations. The unstratified rocks often form the highest ridges and summits of mountains, constituting the apparent