strata, locally interbedded with shales, sandstones, ironstone, and coaly beds (Mountain-limestone); 2nd, a group of gritty and sandy beds, also with some coal (Millstone-grit); 3rd, an argillaceous and sandy group, with little limestone, but much ironstone and bituminous shale, and with numerous intercalated seams and thick beds of the carbonized vegetable matter termed Coal.* Independently of the interest attached to these deposits from the immense accumulation of fossil plants of which many of them are wholly composed, this series involves the consideration of some very remarkable geological phenomena; for the manner in which such extensive layers of carbonized vegetable substances (like the intercalated masses of rock-salt in the red marls of the Trias, p. 541), unmixed with extraneous matter, were produced, is a problem difficult of solution, under certain conditions in which it is presented to our examination. The deposition of coal appears, as we shall presently show, to have taken place under various circumstances; the coal being in some cases associated with fresh-water, and in others with marine organic remains. But, though from the vast importance of mineral fuel in an economical point of view to nations in an advanced state of civilization, and the botanical interest with which such extensive natural herbaria of the paleozoic ages are invested, the coal is generally regarded as constituting the essential feature of this epoch, yet it would be more philosophical to consider these intercalations of carbonized vegetables, like beds of shells, &c., as extraneous and accidental. We have already seen, that the formation of coal was not * In the Crystal Palace Gardens has been constructed a section of the coal-measures, the natural rocks being used as the constituents. In Germany, Dr. Beinert has formed, in his beautiful gardens at Charlottenbrunn, a highly interesting artificial section of the coal-beds, with fine specimens of the fossil plants in place; and Prof. Goeppert has erected a still larger section in the Royal Botanic Gardens at Breslau. See H. R. Goeppert's Der König!. Botan. Garten der Univ. Breslau, 8vo, 1857. confined to the carboniferous system ; * but that beds of this substance (under the various forms of peat, brown-coal, lignite, jet, pitch-coal, cannel-coal, bituminous shale, slate-coal, anthracite, glance-coal, and common coal) have been and will be produced, wherever trees and plants are accumulated in sufficient quantity and under the requisite conditions. The peculiar types of vegetable organization comprised in the flora of this period afford the only distinguishing characters of the beds of coal interpolated in the strata that were deposited during the ages intervening between the close of the Devonian epoch and the commencement of the Permian.t The strata comprised in the Carboniferous series form two natural groups, as shown in the following table; and I propose to consider, in the first place, the general features of the deposits, and their geographical distribution; secondly, the nature and formation of coal, and the characters of the fossil plants of which it is composed; and, lastly, to notice the animal remains, and take a retrospective view of the successive floras which have prevailed on the surface of the earth during the periods embraced by our geological investigations. 2. THE CARBONIFEROUS SERIES.-Though in England simply divisible into a threefold series of calcareous, aren : * See Dr. F. Senft's "Classification and Beschreibung der Felsarten," 8vo, 1857 also Dr. Geinitz's "Steinkohlen-Formation in Sachsen," fol. 1856. A resume of the latter of these valuable works is given by Col. Portlock in his Presidential Address to the Geological Society in 1857 (p. cxxv.). See also Sir R. Murchison's "Siluria.” See remarks on the Coal of the Oolite, p. 513; of the Wealden, p. 405; of the Tertiary, p. 283; and in peat, p. 66. It should be remembered that coal occurs also in the Cretaceous Series (in Saxony and elsewhere), in the Oolitic and Liassic series (at Boll in Wirtemberg, at Seefeld in the Tyrol, and at Walgau in Bavaria, and in Banat, &c.), in the Triassic series of Germany, and in the Permian series of Saxony; also occasionally in the Devonian series: nor are the Silurian and Cambrian, and even the hypogene rocks, without their carbonaceous contents. aceous, and argillaceous beds, the carboniferous system, even in the British Islands, becomes far more complicated in the details of its stratification. In Ireland it commences with an important division, comprising sandy and shaly beds (Yellow Sandstone"* and "Carboniferous Slate," of Griffith), 2000 feet thick; and the limestone itself (5000 feet thick) is there separable into three great divisions. In the western counties of England, and in South Wales, these lowest sandstones, shales, and thin limestones are represented by from 100 to nearly 600 feet of laminated beds, with marine shells, fishes, and terrestrial plants; and in Fifeshire there is a thickness of 1500 feet of equivalent beds. In its extension northward of Derbyshire the Mountain- or Scar-limestone becomes more and more interstrati fied, in its higher portion, with shaly beds; and in the northern counties and in Scotland the great bulk of this characteristic limestone-formation is not only replaced by clays, sands, and calcareous shales, but these are intercalated with numerous coal-beds, often of considerable thickness; thus forming an important series of lower coal-measures, the representatives of which exist also in Europe and in Nova Scotia. The following tabular arrangement exhibits the lithological characters and relations of the carboniferous deposits. * Brit. Assoc. Report, 1852, Sect. p. 43. The "Yellow Sandstone' is correlated by Godwin-Austen (Geol. Quart. Journ. vol. ix. p. 244) with the Pilton and Petherwin beds of North Devon, and referred by him, with the Yellow Sandstones of the Boulonnais and the Cypridina-schists of Germany, to the Upper Devonian. To this member of the Paleozoic series Sedgwick has also provisionally referred it (Phil. Mag. 1854, vol. viii. p. 364, and Geol. Journ. vol. viii. p. 8). Dr. Sharpe, however, inclined to the collocation of the Petherwin group with the Carboniferous system (Geol. Quart. Journ. vol. ix. p. 247). It may therefore be said of these beds of passage from the Devonian to the Carboniferous system, as of the transitional beds between the Silurian and Devonian, the Carboniferous and Permian, the Trias and Lias, the Lias and Oolite, &c., that much exact observation has still to be made in these and other closely related instances. CARBONIFEROUS SYSTEM. UPPER. LOWER. (Lower coalmeasures, or themountainlimestone group.) 1. COAL-MEASURES; -divisible into Upper, 2. MILLSTONE-GRIT.-Coarse quartzose sand- 4. MOUNTAIN-LIMESTONE or SCAR-LIMESTONE. This • In the southern coal-fields two divisions only are apparent: Mur chison's "Silurian System," chap. 6. 3. THE COAL-MEASURES. The bituminous substance termed coal is simply vegetable matter altered by chemical changes, which will hereafter be considered. It occurs in beds that vary from a few inches to a fathom or more in thickness, and are interposed between strata of shale, clay, micaceous sandstone, limestone, and ironstone; alternations of this kind, occupying circumscribed areas, are termed coalbasins. Mr. Bakewell observes that the strata thus disposed may be imitated by a series of mussel-shells or saucers placed one within the other, and having layers of clay interposed. If one side of the series be raised to indicate the general rise of the strata in that direction, and the whole be dislocated by cracks, the general arrangement of the beds and the displacements which they have undergone will be represented; each shell representing a bed of coal, and the partitions of clay imitating the earthy strata which separate the carbonaceous layers. It is the association of iron-ore with the limestone that serves as a flux, and with the mineral fuel required for the reduction of the ore into a metallic state, that has given rise to the numerous iron-foundries established over the sites of our principal coal-fields. The usual characters of a Coalfield, as a series of strata of this kind is termed, are shown in the section of that of South Gloucestershire (Lign. 124, p. 522). Here we perceive that the Devonian or Old Red Sandstone has been elevated into a position almost vertical, and that the Mountain-limestone, which lies immediately upon it, partakes of the same inclination. This is succeeded by conformable beds of Millstone-grit, which are followed by alternations of Coal and shales; the Permian and Triassic |