But the most important observations, we think beyond comparison, that have ever yet appeared on the subject of Stratification, are those of the Reverend JOHN MICHELL, in a paper' On the Cause and Phenomena of Earthquakes,' published in the Philosophical Transactions of 1760.* In this most ingenious production, the author not only states the general appearances of strata, their identity of character, continuity, and uniform thickness, in length and breadth, for many miles, '-the great inclination of the beds in mountainous countries, and their approach to the horizontal position in flat ones; but he explains, most clearly, the arrangement of the strata in England; and this, not as confined to Britain, but as exemplifying a general and beautiful law, which, he asserts, holds universally in all parts of the globe. The situation, he tells us, of the strata, may not unaptly be represented in the following manner.Let a number of leaves of paper, of several different sorts or colours, be pasted upon one another; then bending them up together into a ridge in the middle; conceive them to be reduced again to a level surface, by a plane so passing through them as to cut off all the part that had been raised; let the middle now be again raised a little, and this will be a good general representation of most, if not all large tracts of mountainous countries, together with the parts adjacent, throughout the whole world. From this formation of the earth it will follow, that we ought to meet with the same kinds of earths, stones and minerals, appearing at the surface, in long narrow slips, and lying parallel to the greatest rise of any long ridge of mountains; and so in fact we find them. '—' The Andes of S. America,' he adds, ́ exemplify this structure;' and, in N. America, the great lakes, which give rise to the river St Lawrence, are kept up by a long ridge of mountains, that run nearly parallel to the Eastern coast; and, in descending from them towards the sea, the same sets of strata, in the same order, are generally met with throughout the greatest part of their length. In Great Britain,' he continues, we have another in 6 stance to the same purpose; where the direction of the ridge varies about a point from N. by E. to S. by W.'-' Of which, he subjoins in a note, I could give many undoubted proofs, if it would not too far exceed the limits of my present design. And he further mentions, as an example of the great extent of strata in level tracts the chalky and flinty countries of England and France; which (excepting the interruption of the Channel and the clays, sands, &c. of a few counties) compose a tract of about 300 miles each way.' But he states also, that the highest rise of the ridge, and the inclination of the strata, have very considerable irregularities :--and this often makes it difficult to trace the appearances I have been relating; which, without a general knowledge of the fossil bodies of a large tract of country, it is hardly possible to do." * Vol. LI. Part II. p. 566. Sect. 37 to 49. We know not whether the structure of the districts in America, above referred to, has been confirmed by more recent observations; nor whether by fossil bodies,' in the passage last quoted, the author intended to signify organized remains, as well as mineral productions: But nothing, we think, can be more clear than his exposition of the principle of the stratification of England: And, that he was also acquainted with the detail, is proved, not only by his intimation in the note above alluded to, but by a very interesting document, discovered a few years since among the papers of Mr Smeaton, in the possession of Sir Joseph Banks; in which Mr Smeaton has enumerated, as Mr Michell's account of the south of England strata, veral of the principal beds, with their respective thickness, from the chalk down to the coal, associating as parts of the same stratum, detached portions several miles distant from each other. se The next author of note is WHITEHURST, whose Inquiry into the Original State and Formation of the Earth' was first published in the year 1778, and reprinted, with considerable improvements, in 1786. A great part of this book is infected with that taste for cosmogony which had misled many of the author's predecessors: But if the reader be not repelled by the formidable chapters of the component parts of chaos, whether homogeneous or heterogeneous,' and of the period of human life. • before and after the flood,' he will find some excellent remarks on the organized fossils; and in the latter part of the volume, especially the chapter on the Structure of Derbyshire and other parts of England,' abundant proofs of the acuteness and fidelity of the author's observations. His statements, indeed, concur precisely with those of Mr Michell; the arrangement of the strata being such,' he tells us, that they invariably follow each other as it were in alphabetical order, or as a series of numbers. I do not mean to insinuate, that the strata are alike in all the different regions of the earth, with respect to thickness or quality--for experience shows the contrary; but that in each particular part, how much soever they may differ, yet they follow each other in a regular succession.' p. 178-9. 2d edition. It was my intention,' he says in another place, to have deposited specimens of each stratum, with its productions, in the British Museum, arranged in the same order above each other as they are in the earth; being persuaded, that such a plan would convey a more perfect idea of subterraneous geography, and of the various bodies enclosed in the earth, than words or lines can possibly * This document is so interesting, that we shall insert it in a subsequent page of this article, after the detail of Mr Smith's enumeration. (See hereafter, pp. 332–3.) express;' (p. 204, 205)-a project which has since been executed by Mr Smith. But it is remarkable, that, at the close of his work, the author dwells with much more apparent pleasure on that part which relates to the early ages of the world, and the condition of its Antediluvian inhabitants, who slept away their ⚫ time in sweet repose upon the ever werdant turf,' than upon the truly important and substantial part of his performance. It is difficult to trace the history of WERNER's doctrines, his printed publications being few, and the most important of his tenets having been delivered only in the form of lectures. His Kurze Klassifikation,' a brief but valuable arrangement and description of rocks, published in 1787, has no allusion nor hint at the doctrine of Formations, of which we have given an outline in the preceding Number of this volume, (p. 71.), that term not once occurring in the tract in question. Nor was the distinction of the transition from the floetz class introduced into his arrangement for some years afterwards, grey wacke being placed, in the list of 1787, among the floetz sandstones. The opinions of Werner, as to the origin of the basaltic rocks, were formed after the examination of the Scheibenberg in 1787. The doctrine of formations was delivered in his lectures only, and may be dated as of 1790 or 1791; that of the transition class not until 1795 or 1796. But his theoretic views, as to the deposition of rocks in general, and the configuration of the earth's surface, which, after all, if what relates to the overlying formations be excepted, are little more than a selection from the doctrines of preceding writers, may be collected from his work on Veins, first published in November 1791; at which time it is certain that he was acquainted with the works of Whitehurst, for he has quoted them in the book last mentioned. Mr Jameson has informed us †, that the structure of geological maps, upon *We regret that we have not found, in the scientific journals, any biographical memorial of this distinguished naturalist; but the last public action of his life deserves to be specially recorded. His collection of minerals was singularly rich in valuable and instructive specimens, the accumulation, in fact, of a life devoted solely to mineralogy; yet he surrendered the whole to the School of Mines at Freyberg at a price considerably below the valuation: And, in consequence of the distressed state of Saxony at that period, he accepted only a small part of the reduced sum, reserving a moderate interest upon the remainder, under the form of an annuity, and bequeathing the capital, after his death, to the academy, in which he had been for more than forty years the most distinguished professor. Bergmannisches Journal, 1788, Vol. II. P. 845. the plan of representing by colours the succession of the strata or formations, was also devised by Werner; so that it would seem, upon the whole, that a system coincident with the principles of Mr Smith, so far as they extend, had been delivered in the publications and lectures of Werner (mixed, it is true, with a great alloy of theory) before the period when the latter began his investigation of the neighbourhood of Bath. Since the date of Lister's project for a soil, or mineral map,' there have been published, we believe, some attempts at a geological map of England,-but we have not been so fortunate as to see them; and of the numerous continental maps, those of the older German writers, of Guettard in France, and the recent publications of the Wernerian school, are the only ones that have fallen within our examination. The maps which Buache published between 1745 and 1761, are described as relating more properly to physical geography than to geology; and they proceed upon a visionary hypothesis, about a certain frame-work or skeleton of the earth, which the author imagines to consist in chains of mountains, traversing the islands as well as continents. throughout the face of the globe. The object of Guettard, in his improved collection of 1775, was merely to mark upon ordinary maps, in the characters employed by chemists, the several mineral substances found at each place; a plan obviously very defective, and radically different from that which expresses the order of the strata, by colours. The maps referred to by the late M. Desmarest, as annexed to the Encyclopedie Methodique, have not yet appeared. But that author judiciously insists upon the great instruction to be derived from combining vertical sections, with horizontal maps, and the benefit arising, in general, from even the attempt to reduce to maps, the results of geological investigation. But it is full time to close these prolegomena; for the length To LY of which it might be necessary to apologize, if the increasing q importance of the subject did not render the history of its earlier progress an object of great interest. It is not very easy to give, in a small compass, a correct notion of a performance expressly directed to the eye; but, with the assistance of an ordinary map of England, our readers may probably be enabled to follow us, while we attempt to convey a general idea of what is represented in Mr Smith's Coloured Map and Section, which are now expanded before us, and which have certainly a very striking appearance.-The whole Y VOL. XXIX. NO, 58. of England may be considered as composed of a series of flat or undulating beds, placed one above another, and sloping very gently upwards, from S. E. to N. W.; the general surface, also, of the island, rising pretty uniformly from the east and southern shores, to the mountainous districts of the west, and the beds emerging from beneath each other in succession; so that a traveller from London to North Wales would pass over the out-crop,' as it is colled, or the terminating edge of every stratum in the series.* This accordingly is the course of Mr Smith's vertical section; and in his horizontal map,' the portions of the strata which successively appear at the surface, are marked throughout the whole of their course in different colours. If a line be drawn from Eyemouth, on the coast of Berwickshire, to Liverpool, and through Montgomery in North Wales, Ludlow east of Hereford, and thence to the sea at Teignmouth, on the coast of Devon, (a course sufficiently accurate for this very general view), it will leave to the west the mountainous tracts of Cornwall and Devonshire, Wales, Cumberland and Westmoreland, and Scotland; and after tracing the margin of the range of Transition mountains, which traverses the south of Scotland, from St Abb's head to Solway Firth, it will, in England, mark the boundary between the Primary and Transition rocks to the west, and the more regularly stratified and newer depositions to the eastward. This line coincides, we believe, in its direction, with that of the ridge pointed out by Mr Michell; and we shall find that the structure of England in other respects accords with his description. · If, again, a line be drawn northwards, from Exmouth through Taunton to Tewksbury, and thence, with a moderate curvature, to the east, through Stratford upon Avon, Leicester eastward of Nottingham, Newark, Gainsborough and York, to the mouth of the Tees, it also will divide the island into two portions; of which the western will now include, besides the mountainous regions above mentioned, the remaining metalliferous tract, and all the coal districts; that to the eastward being composed entirely of the more recent stratified rocks; a division, which is attended with a corresponding difference in the pursuits of a proportion of the inhabitants of the two tracts, --and constitutes, in fact, a sort of natural boundary between the agricultural and manufacturing population. This concurrence, throughout so large a part of the island, of the metallic minerals with the coal, which is indispensable to the extraction of * Kidd's Geol. Essay, p. 24. |