A

COMPARATIVE ESTIMATE

OF THE

MINERAL AND MOSAICAL

GEOLOGIES.

CHAPTER I.

THE characters which unfold themselves to our view in examining the substances of which this Globe consists, point out to us some period, or periods, when the order of its structure sustained violent agitation and alteration. In every part of the earth, we encounter unequivocal evidences of disruption, dislocation, and subversion, of its hardest and most solid materials; and we discover remains, equally unequivocal, of organic matter, both animal and vegetable, involved and deeply imbedded in other of its materials, which are soft, or which must have been so at the time when those foreign substances were imbedded within them. Monuments so wonderful, and at the same time universal, naturally stimulated the curiosity of man

to inquire, and to endeavour to ascertain, How, and WHEN, those amazing effects were wrought in the substance of our Globe?

An extended investigation of the same characters, led to this further observation: that the organic substances, are not found indiscriminately in all the materials of which our earth is composed; that they are found only in one order of them, whilst in another order they are never found at all. This remarkable fact, well established, gave occasion to a division of the materials of the earth into two general classes, distinguished chiefly by the presence and the absence of organic remains; and, since it was observed that the materials in which those remains occur, bear in general the appearance of sediment deposited in water, whereas those in which they never occur, wear a crystalline appearance; their respective actual formations were reasonably ascribed to different immediate causes. And, because those which appear to be sedimentary, are observed to be deposited upon those which appear to be crystalline, the latter, which sustain the former, were with equal reason assumed to be of a more ancient date; and, from thence, all the mineral matter of this globe was, for a long time, contemplated scientifically under two principal divisions, entitled primary and secondary; the first of which comprised the crystalline siliceous matter, containing no organic remains, of which kind are granitic rocks; the second comprehended the sedimentary matter, in which alone those re

mains are contained; such are, calcareous, and other earths, containing sea-shells.

But, an intermediary or transition class, of fundamental importance to these inquiries, called also with more propriety and pertinence fragmentary, was afterwards recognised, with great sagacity, and has of late years been introduced between the two; consisting of a modification of the primary class, and comprising the mineral masses formed of aggregated and conglutinated fragments of different primary rocks, but rarely inclosing any organic remains; such is, the coarse sandstone denominated millstone-grit, and that species of compound rock which is called pudding-stone.

Lastly, the accuracy and minuteness of research, has recently superadded to the secondary division a tertiary class, more correctly termed upper-secondary; consisting of superficial detritus, (as gravel beds), and containing relics of terrestrial organic substances.

Thus, the materials of our globe, or more properly of that portion of its superficial crust which the research of man has been able to penetrate, exhibit, in the order of their descending series, the following general characters; distinguished according to the different ages, and the refining progress, of mineralogical investigation: viz.

In this last fourfold distribution of terrestrial matter, the primary class exhibits to us a part of the mineral matter of the globe in its primitive

"The distinction between the four formations, or great divisions "known by the names of primary, intermediary, secondary, and tertiary, appear worthy to be preserved (says M. Humboldt).-The classification "of formations marks the great epochas of nature.-Werner, in creating "geognostic science, has perceived with admirable sagacity, all the rela"tions under which we should view the independence of the primitive, "transition, and secondary formations." (Geog. Essay on the Superp. of Rocks, p. 28, 30, and 80.)

I have not here adopted Mr. Conybeare's ingenious innovation of these long considered and well established arrangements, which innovation increases the number of classes to five, because it excludes all monumental character of epochas, which is of chief importance in Geology, substituting for that of fragmentary, which is historical, that of " roofing slate, &c. &c.,” which is purely economical; and, because it is entirely founded on the positions of the different mineral masses relatively to the great deposit of COAL: a point of reference, which, however advantageous in many prac¬ tical respects it unquestionably is, pertains to geographical and tabular