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Extent of the Province of Geology.
If a stranger, landing at the extremity of England, were to traverse the whole of Cornwall and the North of Devonshire; and crossing to St. David's, should make the tour of all North Wales; and passing thence through Cumberland, by the Isle of Man, to the south-western shore of Scotland should proceed either through the hilly region of the Border Counties, or, along the Grampians, to the German Ocean; he would conclude from such a journey of many hundred miles, that Britain was a thinly peopled sterile region, whose principal inhabitants were miners and mountaineers.
Another foreigner, arriving on the coast of Devon, and crossing the Midland Counties, from the mouth of the Exe, to that of the Tyne, would find a continued succession of fertile hills and valleys, thickly overspread with towns and cities, and in many parts crowded with a manufacturing population, whose industry is maintained by the coal with which the strata of these districts are abundantly inter spersed.*
* It may seen, in any correct geological map of England, that the following important and populous towns are placed upon strata belonging to the single geological formation of the new red sandstone:—Exeter, Bristol, Worcester, Warwick, Birmingham, Lichfield, Coventry, Leicester, Nottingham, Derby, Stafford, Shrewsbury, Chester, Liverpool, Warrington, Manchester, Preston, York, and Carlisle. The population of these nineteen towns, by the census of 1830, exceeded a million.
The most convenient small map to which I can refer my readers, in illustration of this and other parts of the present essay, is the single sheet, re
A third foreigner might travel from the coast of Dorset to the coast of Yorkshire, over elevated plains of oolitic limestone, or of chalk; without a single mountain, or mine, or coal-pit, or any important manufactory, and occupied by a population almost exclusively agricultural.
Let us suppose these three strangers to meet at the termination of their journeys, and to compare their respective observations; how different would be the results to which each would have arrived, respecting the actual condition of Great Britain. The first would represent it as a thinly peopled region of barren mountains; the second, as a land of rich pastures, crowded with a flourishing population of manufacturers; the third, as a great corn-field, occupied by persons almost exclusively engaged in the pursuits of husbandry.
These dissimilar conditions of three great divisions of our country, result from differences in the geological structure of the districts through which our three travellers have been conducted. The first will have seen only those northwestern portions of Britain, that are composed of rocks belonging to the primary and transition series: the second will have traversed those fertile portions of the new red sandstone formation which are made up of the detritus of more ancient rocks, and have beneath and near them, inestimable treasures of mineral coal: the third will have confined his route to wolds of limestone, and downs of chalk, which are best adapted for sheep-walks, and the production of corn.*
duced by Gardner from Mr. Greenough's large map of England, published by the Geological Society of London.
* The road from Bath through Cirencester and Oxford to Buckingham, and thence by Kettering and Stamford to Lincoln, affords a good example of the unvaried sameness in the features and culture of the soil, and in the occupations of the people, that attends the line of direction, in which the oolite formation crosses England from Weymouth to Scarborough.
The road from Dorchester, by Blandford and Salisbury, to Andover and Basingstoke, or from Dunstable to Royston, Cambridge, and Newmarket, affords similar examples of the dull uniformity that we observe in a journey along the line of bearing of the chalk, from near Bridport on the coast of Dorset, to Flamborough Head on the coast of Yorkshire.
Hence it appears that the numerical amount of our population, their varied occupations, and the fundamental sources of their industry and wealth, depend, in a great degree, upon the geological character of the strata on which they live. Their physical condition also, as indicated by the duration of life and health, depending on the more or less salubrious nature of their employments; and their moral condition, as far as it is connected with these employments, are directly affected by the geological causes in which their various occupations originate.
From this example of our own country, we learn that the same constituent materials of the earth are not uniformly continuous in all directions over large superficial areas. In one district we trace the course of crystalline and granitie rocks; in another we find mountains of slate; in a third, alternating strata of sandstone, shale, and limestone; in a fourth, beds of conglomerate rock; in a fifth, strata of marl and clay; in a sixth, gravel, loose sand, and silt. The subordinate mineral contents of these various formations are also different; in the more ancient, are veins of gold and silver, tin, copper, lead, and zinc; in another series, we find beds of coal; in others salt and gypsum; many are composed of freestone, fit for the purpose of architecture; or of limestone, useful both for building and cement; others of clay, convertible by fire into materials of building, and pottery: in almost all we find that most important of mineral productions, iron.
In the same line of direction, or line of bearing of the strata across England, a journey might be made from Lyme Regis to Whitby, almost entirely upon the lias formation? and from Weymouth to the Humber, without onco leaving the Oxford clay. Indeed almost any route, taking a north-east and south-west direction across England, will for the most part pass continuously along the same formation; whilst a line from south-east to north-west, at right angles to the former, will no where continue on the same stratum beyond a few miles. Such a line will give the best information of the order of superposition, and various conditions of the very numerous strata, that traverse our island in a succession of narrow belts, the main direction of which is nearly north-east and south-west. This line has afforded to Mr. Conybeare the instructive section, from Newhaven near Brighton, to Whitehaven, published in his Geology of England and Wales; along which nearly seventy changes in the character of the strata take place.
Again, if we look to the great phenomena of physical geography, the grand distributions of the solids of the globe; the disposition of continents and islands above and amidst the waters; the depth and extent of seas, and lakes, and rivers; the elevation of hills and mountains; the extension of plains; and the excavation, depression, and fractures of valleys; we find them all originating in causes which it is the province of Geology to investigate.
A more minute examination traces the progress of the mineral materials of the earth, through various stages of change and revolution, affecting the strata which compose its surface; and discloses a regular order in the superposition of these strata; recurring at distant intervals, and accompanied by a corresponding regularity in the order of succession of many extinct races of animals and vegetables, that have followed one after another during the progress of these mineral formations; arrangements like these could not have originated in chance, since they afford evidence of law and method in the disposition of mineral matter; and still stronger evidence of design in the structure of the organic remains with which the strata are interspersed.
How then has it happened that a science thus important, comprehending no less than the entire physical history of our planet, and whose documents are co-extensive with the globe, should have been so little regarded, and almost without a name, until the commencement of the present century?
Attempts have been made at various periods, both by practical observers and by ingenious speculators, to estaWish theories respecting the formation of the earth; these have in great part failed, in consequence of the then imperfect state of those subsidiary sciences, which, within the last half century, have enabled the geologist to return from the region of fancy to that of facts, and to establish his conclusions on the firm basis of philosophical induction. We now approach the study of the natural history of the globe, aided not only by the higher branches of physics, but by still more essential recent discoveries, in Mineralogy, and Chemistry, in Botany, Zoology, and comparative Anatomy, By the help of these sciences we are enabled to extract from the archives of the interior of the earth, intelligible records of former conditions of our planet, and to decipher documents, which were a sealed book to our predecessors in the attempt to illustrate subterranean history. Thus enlarged in its views, and provided with fit means of pursuing them Geology extends its researches into regions more vast and remote, than come within the scope of any other physical science except Astronomy. It not only comprehends the entire range of the mineral kingdom, but includes also the history of innumerable extinct races of animals and vegetables; in each of which it exhibits evidences of design and contrivance, and of adaptations to the varying condition of the lands and waters on which they were placed; and besides all these, it discloses an ulterior prospective accommodation of the mineral elements, to existing tribes of plants and animals, and more especially to the uses of man. Evidences like these make up a history of a high and ancient order, unfolding records of the operations of the Almighty Author of the Universe, written by the finger of God himself, upon the foundations of the everlasting hills.