operations which must have taken place in the long period necessary for the production of the latter? We have no formation older than the carboniferous sandstone, from Newcastle to the Grampian mountains of Scotland, with the exception of a few local patches of new red sandstone. The strata of the coal measures are seen tilted up to the surface; a few feet of diluvial gravel and clay are superimposed, but from the period when the matter forming the carboniferous series ceased to be deposited, till the commencement of the system of vegetation which at present exists on the surface, there are no geological records to mark the lapse of any considerable period of time.* That the superimposed diluvial matter was deposited at the period of the elevation of the sandstone rocks, and could not be of a more recent era, is also demonstrable from its containing the same coprolites as the shale of the inferior strata. These clay ironstone nodules are found among this diluvium in all parts of the country, and lying immediately above the tilted up strata of the carboniferous limestone, as well as the various beds of the coal measures; and though they are in composition exactly the same, and contain the same coprolites and portions of fishes and plants, yet many of them have a less compact structure, and are of a lighter ochrey appearance, than

* See Section and Note I.

C

those found in the shale,-a proof that they are not part of those latter broken up, and scattered by a more recent denudatory process, but originally from one common source, part having been enveloped in the shale and part in the diluvial detritus. It may be asserted, that denudation may have swept away any newer formations; but the sharp and unworn edges of the sandstone, the total absence of all traces of a newer formation, while the cracks and fissures of the strata are universally filled with the matter of the superimposed diluvium, in which are mingled portions of the trap rocks, which were the elevating agents indicate the total improbability of the existence of any such newer strata. To the north of the Grampians, again, where the coal series is wanting, we find small patches of the lias formation, accompanied by the new red sandstone, both lying immediately above the old red sandstone conglomerate. Now, as regards the older or primary strata, the south and north sides of the Grampians exhibit an exact similarity, the same central granitic ridge having elevated both at the same period; but on the south of the Tay and Frith of Forth, the carboniferous limestone and sandstone have been largely deposited, while on the north no such deposit has taken place; but instead of it is found a noncarboniferous sandstone in extensive beds, above which are traces of the lias limestone, with its peculiar fossils. Now, the question is, when was this

lias deposited, if not during some part of the era of the coal deposition?

If, then, the northern part of England became dry land at the same period as the south-western, the deposition of part at least of the carboniferous strata must have been contemporary with that of the lias and oolite.

If, on the other hand, the reverse be maintained, that while the south of England was dry land, the northern portions of the island were covered by the ocean, the same arguments apply. For either the deposition of the coal strata was going on contemporaneously with the formation of the oolitic beds, or some equivalent system of operations must have been apparent above the coal measures.

36

SECTION IV.

SOME FORMATIONS HAVE BEEN SUDDENLY

DEPOSITED.

THERE are facts which indicate, that in many situations the deposition of the sedimentary strata was not a gradual and uniform process, the result of successive years or of ages, but that masses of some hundreds of feet in depth were accumulated in a very short space of time, by causes similar

to sudden floods or inundations of rivers. Thus, in the coal strata, trees of from thirty to forty feet in length are found lying very slightly inclined from the vertical position, and crossing numerous beds or layers of strata, among which they are enveloped. This is well displayed in Craigleith Quarry, near Edinburgh, which consists of a mass of sandstone and shale, the depth of which, so far as at present explored, is about two hundred feet. This sandstone, in many places, bears evident marks of having been drifted by some impetuous current of water; and, besides the trunks of trees already mentioned,

3

contains, especially in its superficial layers, immense quantities of the stems of equisetæ, stigmariæ, and other buoyant plants, which appear from their lightness to have floated on the sedimentary mass, and to have thus been deposited near the top; while the heavier trunks of solid wood, after having been saturated with water, and rendered specifically heavier than the surrounding mass, have sunk and become entangled in the consolidating materials. It is impossible to conceive that these trees could have been preserved as they are, with their internal structure so accurately portrayed, had the upper portions been exposed for even a few months to the action of the air. The same remark applies to the trees found in the Newcastle coal fields, and other situations, with their roots, and apparently portions of soil attached to them: these must have been suddenly overturned in the spot where they grew, or, what is more probable, they have been uprooted and drifted by the current; but, in either case, rapidly covered over with the enveloping sand and mud. If we thus, then, have proofs of strata, two hundred feet in depth, having been formed suddenly, may we not apply the same analogy to other strata, where proofs of the fact are not now so evident ?*

But besides mechanical disintegration and accumulation, there are also circumstances in the

* Note II.