proved to be a formation subsequent to the chalk itself; and appear, like all flints, to be the petrified calcareous fluids drained from the whole mass in the course of pressure. It is not easy to account for the manner in which the strata of the chalk were sustained, and kept asunder, whilst the petrifaction of this juice was going on; but this, like many other such difficulties in mineralogy, does not affect the general question; nor ought the dykes of the coal fields to be advanced in opposition to the general principle of formation which we have now been considering.

POSTSCRIPT NOTE TO CHAPTER VIII.

While these sheets are preparing for the press, and while an opportunity is still in my power, I cannot permit it to pass without a few remarks upon an important paper on the Coal Series, lately read before the Yorkshire Philosophical Society,* and which has now been published in the last number of the London and Edinburgh Philosophical Magazine, (for Dec.) This paper is upon the subject of "The Lower Coal Series of Yorkshire." presents one of the many steps in the received systems of Geology, which are slowly, but surely, advancing towards

* October 2d, 1832.

It

that very point for which I am now contending; and the few remarks I have to make upon it, will, I trust, go far to prove, that the hasty conclusions of the Continental Geology, on which our own Schools have all been founded, have led to much contradiction and error, on this highly important branch of our subject.

It has, for some time, been one of the well known facts of Geology, that, as trees and herbs could not, in any common circumstances, or by the common laws of nature, be deposited in a tranquil state in the bed of the sea, the extensive deposits we now discover in the form of repeated and alternating beds of coal, MUST have been deposited in fresh water; and, from this assumption, it has followed, that, wherever vegetable substances have been discovered, in the form of regular strata, even though occasionally accompanied with shells, such formations have received the geological name of LACUSTRINE deposits, as having resulted from the long-continued action of the laws of nature in inland lakes of fresh water.

This idea has, in a great measure, arisen, as I have elsewhere. had occasion to shew, from the deep-rooted error, that we are now inhabiting the same dry land which existed before the Mosaic Deluge; and so misled have we in general been, by this delusion, that, wherever shells have been found in the neighbourhood of the coal strata, it has been assumed, as a matter of course, that they had belonged to such animals as then inhabited the fresh water. It must, also, be kept in mind,. that, as there is often a separation of several hundred feet between the extreme limits of the beds of coal, and that, within that space, there are often many seams of that invaluable deposit, each assumed as having been the result of immense periods of time, as we may have naturally concluded, from the invisible (because visionary) progress of such deposits in the lakes of our own

country, or in the rest of Europe; we are unavoidably led, by the adoption of such a theory, to discard history, and to adopt hypothesis; laying ourselves open, in such instances as I am now about to quote, to the vacillating effects, arising from distinct contradiction.

Mr. John Phillips, the author of the interesting paper above alluded to, says: "The lowest portion of the York"shire coal strata, resting upon the mill-stone grit, pro"duces comparatively but a small quantity of coal; "and this, in general, not of a good quality. But no part of the coal-field is more curious in its geological relations, or more worthy of close study, by those who "desire to penetrate into the history of the production of "coal. We define this lowest coal series very simply,

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may

by saying, that it is included between the mill-stone grit "of Bromley, beneath, and the flag-stone of Elland, above,

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having a thickness of 120, or 150 yards, and inclosing,

near the bottom, two thin seams of coal, one, or both of "them, workable; and several other layers scattered through "its mass, too thin to be worth working. The most regu"lar and continuous of all these coal seams, reaches, in a "few places, to the thickness of 27 or 30 inches, but is generally only about 16. It is worked at various places, "near Leeds, Bradford, Halifax, and Sheffield.

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"It would have been impossible to have traced so thin

a seam of coal, along so extensive a range, without some "peculiar facilities-some points of reference more distinct "than the varying quality of the coal, and the still more

irregular fluctuations of the SANDSTONES and SHAles. "This coal seam is covered by a roof, unlike that of any "other coal bed, above the mountain limestone, in the British "Islands; for, instead of containing only the remains of plants, or FRESH WATER SHELLS, it is filled with a "considerable diversity of MARINE SHELLS, belonging to

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"the genera Pecten, and Ammonites; and, in one locality, near Halifax, specimens of Orthocera, Ostrea, and scaly fish, have been obtained from certain nodular argillo-calcareous concretions, called Baum Pots, lying over it. The uniform occurrence of the Pectens, and Ammonites, through so wide a range, over one parti"cular thin bed of coal, while they are not found in any "other part of the coal strata, is one of the most curious

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phænomena yet observed concerning the distribution of organic remains, and will, undoubtedly, be found of the highest importance in all deductions relating to the cir"cumstances which attended the PRODUCTION OF COAL."

Mr. Phillips then proceeds to give sections of the whole series, which, as in other coal fields, consists of alternating strata of sandy, and argillaceous deposits, exactly similar, in their general character, to what I have already had occasion to exhibit; and containing, in several instances, the fossil remains of shells and plants.

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He then continues: "In the upper coal series of Northumberland, Durham, Yorkshire, and Derbyshire, are “several most extensive layers of bivalve shells, commonly "called muscle-bands, and referred to the genus Unio, from which the FRESH-WATER origin of those coal de

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posits has been inferred. It was, therefore, with ex"treme gratification, that I found, in passing through "Mr. Rawson's colliery, at Swan Banks, in the midst of "the series above described, Two layers of these shells, "one of them about the middle of the series, considerably ABOVE THE PECTEN COAL; the other near the bottom, "and considerably BELOW that coal.”

Mr. Phillips then reasons upon the 66 PERIODICAL "return of the marine element into its ancient receptacle, after THAT had been, for some time, occupied by FRESH

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WATER, and its few inhabitants," in much the same

way by which the theories of Cuvier attempt to account for the stratifications in the Paris chalk basin.

After what has been already said on the more consistent and historical source of such deposits, it is only necessary, in this place, to add, that so unquestionable a proof of MARINE agency, in various parts of the coal basins of England, must shake to their foundations the theories of LACUSTRINE deposits; and, until it can be shewn in our own lakes, or in those of the European Continent, not only that such extensive ligneous deposits are now going on in their beds, but, also, that distinct STRATIFICATION can, under any circumstances, take place, without the action of the tides and currents, we must continue to look upon such vague and contradictory theories, as nothing better than empty dreams, which leave the mind in a confused and bewildered state, without the reason being able to attain any sound or solid ground upon which securely to repose.*

* For further most important evidence on this subject, see the Supplementary Note to Chapter XI.