The World Before the Deluge

We thus see that the United States holds a secondary place as a coal-producing country; raising one-eleventh part of the out-put of the whole of Europe, and about one-eighth part of the quantity produced by Great Britain.

The Coal-measures of England and Scotland cover a large area; and attempts have been made to estimate the quantity of fuel they contain. The estimate made by the Royal Commission on the coal in the United Kingdom may be considered as the nearest; and,

QUANTITY OF COAL IN UNITED KINGDOM,

in this Report, lately published, it is stated that in the ascertained coal-fields of the United /Kingdom there is an aggregate quantity of 146,480,000,000 tons of coal, which may be reasonably expected to be available for use. In the coal-field of South Wales, ascertained by actual measurement to attain the extraordinaiy thickness of i i.ooo feet of Coal-measures, there are 100 different seams of coal, affording an aggregate thickness of 120 feet, mostly in thin beds, but varying from six inches to more than ten feet. Professor J. Phillips

Fig. 71. — Contortions of Coal-beds.

estimates the thickness of the coal-bearing strata ot the north of England at 3,000 feet; but these, in common with all other coal-fields, contain, along with many beds of the mineral in a more or less pure state, interstratified beds of sandstones, shales, and limestone; the real coal-seams, to the number of twenty or thirty, not exceeding sixty feet in thickness in the aggregate. The Scottish Coal-measures have a thickness of 3,000 feet, with similar intercalations of other carboniferous rocks. The coal-basin of Belgium and of the north of France forms a nearly continuous zone from Liege, Namur, Charleroi, and Mons, to Valenciennes, Douai, and Bethune. The beds of coal there are from fifty to one hundred and ten in number, and their thickness varies from ten inches to six feet. Some coal-fields which are situated beneath the Secondary formations of the centre and south of France

possess beds fewer in number, but individually thicker and less regularly stratified. The two basins of the Saone-et-Loire, the

Fig. 72. — Cycas circinalis (living form).

principal mines of which are at Creuzot, Blanzy, Montchanin, and Epinac, only contain ten beds; but some of these (as at Montchanin) attain 30, 100, and even 130 feet in thickness. The coal-basin of

the Loire is that which contains the greatest total thickness of coal-beds: the seams there are twenty-five in number. After those of the North — of the Saone-et-Loire and of the Loire — the principal basins in France are those of the Allier, where very imj)ortant beds are worked at Commentry and Bezenet; the basin of Brassac, which commences at the confluence of the Allier and the Alagnon; the basin of the Aveyron, known by the collieries of Decazeville and Aubin; the basin of the Gard, and of Grand'-Combe. Besides these principal basins, there are a great many others of scarcely less importance, which yield annually to France from six to seven million tons of coal. The seams of coal are rarely found in the horizontal position in ^rhich their original formation took place. They have been since much crumpled and distorted, forced into basin-shaped cavities, with minor undulations, and affected by numerous flexures and other disturbances. They are frequently found broken up and distorted by faults, and even folded back on themselves into zigzag forms, as represented in the engraying (Fig. 71, p. 167), which is a mode of occurrence common in all the Coal-measures of Somersetshire and in the basins of Belgium and the north of France. Vertical pits, sunk on coal which has been subjected to this kind of contortion and disturbance, sometimes traverse the same beds many times.

I/O

PERMIAN PERIOD.

The name "Permian" was proposed by Sir Roderick I. Murchison^ in the year 1841, for certain deposits which are now known to terminate upwards the great primeval or Palasozoic Series.*

This natural group consists, in descending order, in Germany, of the Zechstein, the Kupfer-schiefer, Roth-liegende, &c. In England it is usually divided into Magnesian Limestone or Zechstein, with subordinate Marl-slate or Kupfer-schiefer, and Rothliegende. The chief calcareous member of this group of strata is termed in Germany the " Zechstein," in England the " Magnesian Limestone;" but, as magnesian limestones have been produced at many geological periods, and as the German Zechstein is only a part of a group, the other members of which are known as " Kupfer-schiefer" (" copper-slate"), " Roth-todt-liegende " (the "Lower New Red" of English geologists), &c., it was manifest that a single name for the whole was much needed. Finding, in his examination of Russia in Europe, that this group was a great and united physical series of marls, limestones, sandstones, and conglomerates, occupying a region much larger than France, and of which the Government of Perm formed a central part. Sir Roderick proposed that the name of Permian, now in general use, should be thereto applied.

Extended researches have shown, from the character of its embedded organic remains, that it is closely allied to, but distinct from, the carboniferous strata below it, and is entirely distinct from the overlying Trias, or New Red Sandstone, which forms the base of the great series of the Secondary rocks.

Geology is, however, not only indebted to Sir Roderick Murchison for this classification and nomenclature, but also to him,

in conjunction with Professor Sedgwick, for the name " Devonian^' as an equivalent to " Old Red Sandstone;" whilst every geologistknows that Sir R. Murchison is the sole author of the Silurian System.

♦ See "Siluria," p. 14. Philosophical Mag, ^ Srd series, vol. xix., p. 419.

XII.—Ideal landscape of the Permian Period.

The Permian rocks have of late years assumed great interest, particularly in England, in consequence of the evidence their correct determination affords with regard to the probable extent, beneath them, of the coal-bearing strata which they overlie and conceal; thus tending to throw a light upon the duration of our coal-fields, one of the most important questions of the day in connection with our industrial resources and national prosperity.

On the opposite page an ideal view of the earth during the Permian period is represented (Pl. XIL). In the background, on the right, is seen a series of syenitic and porphyritic domes, recently thrown up; while a mass of steam and vapour rises in columns from the midst of the sea, resulting from the heat given out by the porphyries and syenites. Having attained a certain height in the cooler atmosphere, the columns of steam become condensed and fall in torrents of rain. The evaporation of water in such vast masses being necessarily accompanied by an enormous disengagement of electricity, this imposing scene of the primitive world is illuminated by brilliant flashes of lightning, accompanied by reverberating peals of thunder. In the foreground, on the right, rise groups of Tree-ferns,. Lepidodendra, and Walchias, of the preceding period. On the seashore, and left exposed by the retiring tide, are Molluscs and Zoophytes peculiar to the period, such as Producfa, Spirifera, and Encrinites; pretty plants — the Astcrophyllitcs — which we have noticed in our description of the Carboniferous age, are growing at the water's edge, not far from the shore.

During the Permian period the species of plants and animals were nearly the same as those already described as belonging to the Carboniferous period. Footprints of reptilian animals have been found in the Permian beds near Kenilworth, in the red sandstones of that age in the Vale of Eden, and in the sandstones of Corncockle Moor, and other parts of Dumfriesshire. These footprints, together with the occurrence of current-markings or ripplings, sun-cracks, and the pittings of rain-drops impressed on the surfaces of the beds, indicate that they were made upon damp surfaces, which afterwards became dried by the sun before the flooded waters covered them with fresh deposits of sediment, in the way that now happens during variations of the seasons in many salt lakes.* M. Ad. Brongniart has described the forms of the Permian flora as being intermediate between those of the Carboniferous period and of that which succeeds it.

• A. C. Ramsay, *'0n the Red Rocks of England." Quart. Jour, Ceol Soc.^ Tol. xxvii., p. 246.

Although the Permian flora indicates a dimate similar to that which prevailed during the Carboniferous period, it has been pointed out by Professor Ramsay, as long ago as 1855, that the Permian breccia of Shropshire, Worcestershire, &c., affords strong proofs of being the result of direct glacial action, and of the consequent existence at the period of glaciers and icebergs.

That such a state of things is not inconsistent with the prevalence of a moist, equable, and temperate climate, necessary for the preservation of a luxuriant flora like that of the period in question, is shown in New Zealand; where, with a climate and vegetation approximating to those of the Carboniferous period, there are also glaciers at the present day in the southern island.

Professor King has published a valuable memoir on the Permian fossils of England, in the Proceedings of the Palasontographical Society, in which the following Table is given (in descending order) of the Permian system of the North of England, as compared with that of Thuringia:—

North of England. Thuringia. Mineral Character.

I. Crystalline, earthy, 1 compact, and oolitic [• I. Stinkstein. i. Oolitic limestones, limestones. )

" ^bTeSS&ot ] - R^-chwacke,... Conglcnera.es.

3. FossiliferousUmestone ( 3- UpP^r^.^t^JSn" ] 3- Marlstones. 4. Compact limestone 4. Lower Zechstein. 4. Magnesian limestones. j 5. Mergel-Schiefer or ) 5. Red and green grits 5. Marl-slate. j Kupferschiefer. ] with copper-ore. 6. sandsofvariouscoloursLower sandstones, and ') ^'^ ^^, odteliegende',. ^. j(.C ^- ^"^^^^^gypsumsalt. limestoneand whitewith

At the base of the system lies a band oilower sandstone {^o. 6) of various colours, separating the Magnesian Limestone from the coal in Yorkshire and Durham; sometimes associated with red marl and gypsum, but with the same obscure relations in all these beds which usually attend the close of one series and the commencement of another; the imbedded plants being, in some cases, stated to be identical with those of the Carboniferous series. In Thuringia the Rothliegende^ or red-Iyer, a great deposit of red sandstone and conglomerate, associated with • porphyry, basaltic trap, and am)^gdaloid, lies at the base of the system. Among the fossils of this age are the sihcified trunks of Tree-ferns {Psaro7iiiis), the bark of which is sur-

PERMIAN PERIOD.

175

rounded by dense masses of air-roots, which often double or quadruple the diameter of the original stem; in this respect bearing a strong resemblance to the living arborescent ferns of New Zealand.

The marl-slate (No. 5) consists of hard calcareous shales, marl-slates, and thin-bedded limestone, the whole nearly thirty feet thick in Durham, and yielding many fine specimens of Ganoid and Placoid fishes—Palæoniscus, Pygopterus, Cœlacanthus, and Platysomus—genera which all belong to the Carboniferous system, and which Professor King thinks probably lived at no great distance from the shore; but the Permian species of the marl-slate of England are identical with those of the copper-slate of Thuringia. Agassiz was the first to point out a remarkable peculiarity in the forms of the fishes which lived before and after this period. In most living fishes the trunk seems to terminate in the middle of the root of the tail, whose free margin is “homocercal” (even-tail), that is, either rounded, or, if forked, divided into two equal lobes. In Palæoniscus, and most Palæozoic fishes, the axis of the body is continued into the upper lobe of the tail, which is thus rendered unsymmetrical, as in the living sharks and sturgeons. The latter form, which Agassiz termed “heterocercal” (unequal-tail) is only in a very general way distinctive of Palæozoic fishes, since this asymmetry exists, though in a minor degree, in many living genera besides those just mentioned. The compact limestone (No. 4) is rich in Polyzoa. The fossiliferous limestone (No. 3), Mr. King considers, is a deep-water formation, from the numerous Polyzoa which it contains. One of these, Fenestella retiformis, found in the Permian rocks of England and Germany, sometimes measures eight inches in width.