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almost exclusively from strata of the Transition series. Examples of Coal in any of the Secondary strata are few and insignificant; whilst the Lignites of the Tertiary formations, although they occasionally present small deposites of compact and useful fuel, exert no important influence on the economical condition of mankind.*
It remains to consider some of the physical operations on the surface of the Globe, to which we owe the disposition of these precious Relics of a former world, in a state that affords us access to inestimable treasures of mineral Coal.
We have examined the nature of the ancient vegetables from which Coal derives its origin, and some of the processes through which they passed in their progress towards their mineral state. Let us now review some farther important geological phenomena of the carboniferous strata, and see how far the utility arising from the actual condition of this portion of the crust of the globe, may afford probable evidence that it is the result of Foresight and Design.
It was not enough that these vegetable remains should have been transported from their native forests, and buried at the bottom of ancient lakes and estuaries, and seas, and there converted into coal; it was farther necessary that great and extensive changes of level should elevate, and convert into dry and habitable land, strata loaded with riches, that would for ever have remained useless, had they continued entirely submerged beneath the inaccessible depths, wherein they were formed; and it required the exercise of some of the most powerful machinery in the Dynamics of the terrestrial globe, to effect the changes that were requisite to render thase Elements of Art and Industry accessible to the labour and ingenuity of man. Let us briefly examine the results that have been accomplished.
* Before we had acquired by experiment some extensive knowledge of the contents of each series of formations which the Geologist can readily identify, there was no d priori reason to expect the presence of coal in any one Series of strata rather than another. Indiscriminate experiments in search of coal, in strata of every formation, were therefore desirable and proper, in an age when even the name of Geology was unknown; but the continuance of such Experiments in districts which are now ascertained to be composed of non-carboniferous strata of the Secondary and Tertiary Series, can no longer be justified, since the accumulated experience of many years has proved, that it is only in those strata of the Transition Series which have been designated as the Carboniferous Order, that productive Coal-mines on a large scale have ever been discovered.
The place of the great Coal formation, in relation to the other series of strata, is shown in our first section (PI. 1. Fig. 14.) This ideal section represents an Example of dispositions which are repeated over various areas upon the crust of the Globe.*
The surface of the Earth is found to be covered with a series of irregular depressions or Basins, divided from one another, and sometimes wholly surrounded by projecting portions of subjacent strata, or by unstratified crystalline rocks, which have been raised into hills and mountains, of various degrees of height, direction and continuity. On either side of these more elevated regions, the strata dip with more or less inclination, towards the lower spaces between one mountain range and another. (See PI . 1.)
This disposition in the form of Troughs or Basins, which is common to all formations, has been more particularly demonstrated in the Carboniferous Series, (See PI. 65. Fig. 1, 2, 3,) because the valuable nature of beds of Coal often causes them to be wrought throughout their whole extent.
One highly beneficial result of the basin-shaped disposition of the Carboniferous strata has been, to bring them all to the surface around the circumference of each Basin, and to render them accessible, by sinking mines in almost every part of their respective areas; (See PI, 65. Figs. 1, 2, 3.) An uninterrupted inclination in one direction only, would have soon plunged the lower strata to a depth inaccessible to man.
* The Coal Formation is here represented as having partaken of the same elevatory movements, which have raised the strata of all formations towards the mountain Ridges, that separate- one basin from another basin.
The Basin of London, (PI. 68.) affords an example of a similar disposition of the Tertiary strata reposing on the Chalk. The Basins of Paris, Vienna, and of Bohemia, afford other examples of the same kind. (See PI. 1. Figs. 24—28.)
The Secondary and Transition strata of the central and North Western districts of England, are marginal portions of the great geological Basin of Northern Europe; and their continuations are found in the plains, and on the flanks of mountain regions on the Continent.*
These general dispositions of all strata in the form of Troughs or Basins have resulted from two distinct systems of operations, in the economy of the terraqueous globe; the first producing sedimentary deposites, (derived from the materials of older rocks, and from chemical precipitates,) on those lower spaces into which the detritus of ancient elevated regions was transported by the force of water; the second raising these strata from the sub-aqueous regions in which they were deposited, by forces analogous to those whose effect we occasionally witness in the tremendous movements of land, that form one of the phenomena of modern Earthquakes.
* The section (PI. 66. Fig. 1.) shows the manner in which the Strata of the Transition Series are continued downwards between the Coal formation and the older members of the Grauwacke formation through a series of deposites, to which, Mr. Murchison has recently assigned the name of the "Silurian system." This Silurian System is represented by No. 11, in our Section, Fig. 1. The recent labours of Mr. Murchison in the border counties of England and Wales have ably filled up what has hitherto been a blank page, in the history of this portion of the vast and important Systems of rocks, included under the Transition series; and have shown us the links which connect the Carboniferous system with the older Slaty rocks. The large group of deposites to which he has given the appropriate name of Silurian system, (as they occupy much of the Territory of the ancient Silures,) admits of a four-fold division, which is expressed in the section PI. 66. Fig. 1. This section represents the exact order of succession of these Strata in a district, which must henceforth be classic in the Annals of Geology.
In September, 1835,1 found the three uppermost divisions of this system, largely developed in the same relative order of succession on the south frontier of the Ardennes, between the great Coal formation and the Grauwacke. See Proceedings of the Meeting of the Geological Society of France at Mezieres and Namur, Sep. 1835, Bulletin de la Sociitc Giologique de France, Tom VIL) The same subdivisions of the Silurian system, maintain their relative place and importance over a large extent of the mountainous district of the Eifel, between the Ardennes and the Valley of the Rhine; and are continued East of the Rhine through great part of the duchy of Nassau. (Stints Gebirgs-Karte, von dem Herzogthura-Nassau. Wiesbaden,
I am relieved from the necessity of entering into details respecting the history of the Coal Fields of our own country, by the excellent summary of what is known upon this interesting subject, which has recently been given in a judicious and well selected anonymous publication, entitled The History and Description of Fossil Fuel, the Collieries, and Coal Trade of Great Britain. London, 1835.
The most remarkable accumulations of this important vegetable production in England are in the Wolverhampton and Dudley Coal Field, (PI. 65, Fig. 1,) where there is a bed of coal, ten yards in thickness. The Scotch Coal field near Paisley presents ten beds, whose united thickness is one hundred feet. And the South Welsh Coal Basin (PI. 65, Fig. 2,) contains, near Pontypool, twenty-three beds of coal, amounting together to ninety-three feet.
In many Coal fields, the occurrence of rich beds of iron ore in the strata of slaty clay, that alternate with the beds of coal, has rendered the adjacent districts remarkable as the site of most important Iron foundries; and these localities, as we have before stated, (p. 65,) usually present farther practical advantage, in having beneath the Coal and Iron ore, a substratum of Limestone, that supplies the third material required as a flux to reduce this ore to a metallic state.
Our section, PI. 65, Fig. 1, illustrates the result of these geological conditions in enriching an important district in the centre of England, near Birmingham, with a continuous succession of Coal mines, and Iron foundries. A similar result has followed from the same causes, on the north-east frontier of the enormous Coal basin of South Wales, in the well-known Iron foundries, near Pontypool and Merthyr Tydfil,* (See PI. 65, Fig. 2.) The beds of shale in the lower region of this coal field are abundantly loaded with nodules of argillaceous iron ore, and below these is a bed of millstone grit capable of enduring the fire, and used in constructing the furnaces; still lower is the limestone necessary to produce the fusion of the ore. PI. 65, Figs. 1, 2.
The great iron foundries of Derbyshire, Yorkshire, and the south of Scotland, afford other examples of the beneficial results of a similar juxtaposition, of rich argillaceous iron ore and coal.
"The occurrence of this most useful of metals," says Mr. Conybeare,f "in immediate connexion with the fuel requisite for its reduction, and the limestone which facili
* In the Transactions of the Natural History Society of Northumberland, Durham, and Newcastle, vol. i. p. 114, it is stated by Mr. Foster, that the quantity of iron annually manufactured in Wales is about 270,000 tons, of which about three-fourths are made into bars, and one-fourth sold as pigs and castings. The quantity of coal required for its manufacture will be about five tons and a half, for each ton of iron. The annual consumption of coals by the iron works will therefore be about 1,500,000 tons. The quantity used in the smelting of copper ore imported from Cornwall, in the manufacture of tin plate, forging of iron for various purposes, and for domestic uses, may be calculated at 350,000 tons, which makes altogether the annual consumption of coal in Wales, 1,850,000 tons. The quantity of iron manufactured in Great Britain in the year 1827 was 690,000 tons. The production of this immense quantity was thus distributed,