154. In the Neptunian system, as improved by WERNER, an attempt is made to take off the force of such instances as are produced in § 8, 9, and 152, &c. by distinguishing rocks, as to their formation, into three different orders, the primitive, the intermediate, and the secondary, or, to speak more properly, into primary, secondary, and tertiary. The same mineralogist distinguishes, among the materials of these rocks, between what he terms chemical and mechanical deposits. By mechanical deposits, are understood sand, gravel, and whatever bears the mark of fracture and attrition; by chemical deposits, those which are regularly crystallized, or which have a tendency to crystallization, and in which the action of mechanical causes cannot be traced. This distinction is founded in nature, and proceeds on real and palpable differences; but the application made of it to the three kinds of strata just enumerated, seems by no means entitled to the same praise. The primitive rocks contain, it is said, none but chemical deposits, and are entirely composed of them: the intermediate contain a mixture of both, and also some vestiges of organized bodies: the secondary consist almost entirely of the mechanical, or of the remains of such bodies, with little of the chemical. The first of these, then, are held to contain no mark or vestige whatsoever of any thing more ancient than themselves, and are, in the strictest sense, primeval, or formed of the first materials, deposited by the immense ocean which originally encompassed the globe. After them were formed the intermediate, mostly consisting of chemical deposits, but containing also some animal remains, and some spoils from the land, subjected to the various kinds of destruction, which even then made a part of the order of nature. These rocks, it is alleged, are chiefly argillaceous, are less indurated than the primary, and not intersected by veins of quartz. The secondary were formed from the remains of the other two, and contain more mechanical deposits than any other. This sketch of what I understand to be Werner's opinion concerning the different formation of the strata, is chiefly taken from a view of his system, in the _Journal de Physique_ for 1800.