And lastly, on this branch of evidence, we find Mr. Miller alluding to the same upheaving principle, when describing, with his wonted powers of imagery, some examples in point from the scenes of his geological labours: would that we had had the benefit of the same clear and comprehensive sketching applied to more extended fields of research.

"The natural boundaries of the geographer," says he, "are rarely described by right lines. Wherever these occur, however, the geologist may look for something remarkable. There is one very striking example furnished by the North of Scotland. The reader, in consulting a map of the kingdom, will find that the edge of a ruler laid athwart the country, in a direction from south-west to north-east, touches the whole northern side of the great Caledonian valley, with its long straight line of lakes; and onwards, beyond the valley's termination at both ends, the whole side of Loch Eil and Loch Linnhe, and the whole of the abrupt and precipitous northern shores of the Moray Frith, to the extreme point of Tarbat Ness; a right line of considerably more than a hundred miles. Nor does the geography of the globe furnish a line better defined by natural marks. There is both rampart and fosse. On the one hand we have the rectilinear lochs and lakes, with an average profundity of depth more than equal to that of the German Ocean, and, added to these, the rectilinear lines of frith; on the other hand, with but few interruptions, there is an inclined wall of rock, which rises at a steep angle in the interior to nearly two thousand feet over the level of the great canal, and overhangs the sea towards its northern termination, in precipices of more than a hundred yards.

"The direction of this rampart and fosse, this Roman wall of Scottish geological history, seems to have been that in which the volcanic agencies chiefly operated in upheaving the entire island from the abyss. The line survives as a sort of foot-track, hollowed by the frequent tread of earthquakes, to mark the course in which they journeyed. Like one of the great lines in a trigonometrical survey, it enables us, too, to describe the lesser lines, and to determine their average bearing. The volcanic agencies must have extended athwart the country from south-west to north-east. Mark in a map of the island, all the better if it be a geological one, the line in which most of our mountain ranges stretch across from the German Ocean to the Atlantic; the line, too, in which our friths, lochs, and bays, on both the eastern and western coasts, and especially those

of the latter, run into the interior. Mark, also, the line of the geological formations, where least broken by insulated groups of hills; the line, for instance, of the old red sandstone belt, which flanks the southern base of the Grampians; the nearly parallel line of our Scottish coalfield, in its course from sea to sea; the line of the grauwacke, which forms so large a portion of the South of Scotland; the line of the English coal-field, of the lias, of the oolite, of the chalk, and, how, in this process of diagonal lining, if I may so speak, the south-eastern portion of England comes to be cut off from the secondary formation altogether; and, but for the denudation of the Valley of the Weald, would have exhibited only tertiary depositions. In all these lines, whether of mountains, lakes, friths, or formations, there is an approximation to parallelism with the line of the great Caledonian Valley; proofs that the upheaving agency from beneath must have acted in this direction from some unknown cause, during all the immensely extended term of its operations, and along the entire length of the island. It is a fact, not unworthy of remark, that the profound depths of Loch Ness undulated in strange sympathy with the reeling towers and crashing walls of Lisbon, during the great earthquake of 1755; and that the impulse, true to its ancient direction, sent the waves in huge furrows to the north-east and the south-west."*

That mountains and mountainous chains are, generally, more elevated the nearer they are to the equatorial region, we advert to the testimony afforded by the various graduated scales, or synoptic views of the most noted mountains of the world, and, also, to the following more general evidence, which incidentally occur in scientific works.

"It is well known," says the accomplished author of the Connexion of the Sciences, "that the continents at the equator, are more elevated than they are in higher latitudes."†

Professor Phillips, when endeavouring to disprove the assumption, that the globe might, by natural changes, be worn down by rains and waves, from a perfect sphere to a spheroid of rotation, after showing what would, under such a state of matters have been the case near to the equator, goes on to say: "But nothing of the kind appears; on the contrary, the distribu† Page 56.

Old Red Sandstone, pp. 137-139.

tion of land and water is excessively irregular, &c.; and the equatorial regions include some of the highest mountains on the globe.'

What has hitherto been brought forward refers to external appearances only; endeavouring to prove by them, as far as they are available, that the mountain chains owe their elevations to the protorotation of the earth, and its dynamical consequences; and certainly, when the evidences which have been adduced from geological writers are compared with the effects which we anticipated would be produced by the dynamical forces, engendered by the first diurnal revolution of the earth, upon the concentric rocky masses of the primitive sphere, we are borne out in maintaining, that this external branch of the evidence goes a great way towards convincing us, that the peculiar structure of the mineral crust of the earth is due to the cause we anticipated, and which we have all along maintained it did. But we must now proceed, in further support of this position, to carry our investigations into the more intimate formation of those mountains, and into the mineralogical structure of the rocks which compose them. To effect this, we shall commence by adducing the reasons we have for supposing, that the rocks of which they are composed have been moved en masse from the positions wherein they were originally formed. In consequence of the simplicity and homogenity of the mineralogical composition, as well as the amorphous nature of the unstratified rocks, they do not, of themselves, present a sufficient prominency of character, on which to raise a conclusive chain of reasoning; but, fortunately, this difficulty is removed when we direct our enquiries to those stratified masses which immediately rest upon or overlie them; and with whose elevation they are so intimately associated that, by their means, we can reason regarding the primary rocks with a degree of certainty which banishes all doubt from the mind. We shall, therefore, pursue this method of argument.

By the fourteenth Theorem it will be seen, "That the stratified rocks afford sufficient evidence of having been formed in succession, horizontally and tranquilly by deposition from

* Treatise, pp. 7, 8, which please see.

water; although, in many instances, bearing marks of the water having been gently undulated. That they differ in many respects from the primary amorphous masses." The concluding term of this Theorem being irrelevant to our present subject, it is not recapitulated.

As the evidences on which these opinions rest are of importance to our future argument, we shall give several of them at some length.

"Stratified rocks," says Dr. M'Culloch, "have been deposited from water. They have been produced from fragments, or from dissolved substances, or from both. They have been consolidated by mechanical forces, or by chemical actions, or by both. They were once horizontal in position, or nearly so, and their positions are now various. They were once continuous and straight planes, or nearly so, as far as their extent; and they are now bent, fractured, and separated. They were once unmixed with stratified rocks, and they are now intermixed with them. They were once, or oftener, below water, and they are now above it. They are repeated in consecutive and parallel order of the same, or different kinds. With rare exceptions, every stratum is of later origin than the one next below it....

The term stratum, or bed, carries its own definition with it; its extent, according to the prolongation of its great opposing planes, being generally far greater than its thickness. A repetition of such beds forms a series of strata; and the term stratification implies the mode of their deposition, to whatever cause that may be attributed. The term stratification therefore implies a cause as well as a mode of form and disposition; and that cause is assumed or proved to consist in a deposition from water, of materials that have been suspended and dissolved in it."*

"The aqueous rocks," observes Mr. Lyell, "sometimes called the sedimentary, or fossiliferous, cover a larger part of the earth's surface than any others. These rocks are stratified, or divided into distinct layers or strata.

"Fossil shells of forms, such as now abound in the sea, are met with far inland, both near the surface and at a great depth below it. They occur at all heights above the level of the ocean, having been observed at an elevation of from 8,000 to 9,000 feet in the Alps and

* Geology, vol i. pp. 12, 67.

Pyrenees, of more than 13,000 feet in the Andes, and above 16,000 feet in the Himalayas. (Geogr. Journal, vol. iv. p. 64.) These shells belong mostly to marine testaceæ, but in some places exclusively to forms characteristic of lakes and rivers. Hence it is concluded that some ancient strata were deposited at the bottom of the sea, and others in lakes and estuaries. . . .

"We have now pointed out one great class of rocks, which, however they may vary in mineral composition, colour, grain, or other characters, external and internal, may, nevertheless, be grouped together as having a common origin. They have all been formed under water, in the same manner as accumulations of sand, mud, shingle, banks of shells, reefs of coral, and the like, and are all characterized by stratification or fossils, or by both."

And again

"Before entering into a more detailed investigation of the stratified rocks, it will be advisable to say something of the ordinary materials of which such strata are composed. These may be said to belong principally to three divisions, the arenaceous, the argillaceous, and the calcareous, which are formed respectively of sand, clay, and carbonate of lime. Of these, the sandy masses are chiefly made up of siliceous or flinty grains. The clayey, of a mixture of siliceous matter, with usually about one-fourth in weight of aluminous earth, and, lastly, the limestone or calcareous rocks consist of carbonic acid and lime.

"It has generally been said, that the upper and under surfaces of strata, or the planes of stratification are parallel. Although this is not strictly true, they make an approach to parallelism, for the same reason that sediment is usually deposited at first in nearly horizontal layers.

"The ripple mark so common on the surface of sandstones of all ages, seems to have originated in the drifting of materials along the bottom of the water in a manner very similar to that which may explain the inclined layers above described. This ripple is not entirely confined to the beach between high and low water marks, but is also produced on sands which are constantly covered by water."*

At another place he says

"In short, the universal fluidity of the crystalline formations of the earth's crust, can only be understood in the same sense as the

* Please refer to the diagram given at this place in Mr. Lyell's work.