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Malvern hills,' 1811;* Mr Weaver, on part of Gloucestershire,' 1819;† and Mr James Yates, 1825, 'on the structure of the Border Country,' &c.‡

The AUTHOR of this volume, whose acquaintance with geology began, we believe, about 1825, applied himself with great energy to his new pursuit; and his progress may be traced in the proceedings of the Geological Society, of which he soon became an active member. One of his first papers-on the existence of coal in the oolitic series, at Brora on the coast of Scotland, was produced in 1827; and Professor Sedgwick having afterwards joined him in that district, their enquiries were extended to the Isle of Arran,§ and to an examination of the old conglomerates and other strata, between the primary and the oolitic series of the north of Scotland;¶-a task which greatly contributed to their correct acquaintance with the ancient rocks, especially the old red sandstone, and to extended views of the phenomena produced by igneous action, and the intrusion of plutonic masses among the sedimentary deposits. The result of these various researches appears in the 'Geological Transactions.'

The author's knowledge of the igneous rocks was enlarged by an expedition, with Mr Lyell, to the volcanic regions of central France, in the summer of 1822; the results of which also have been printed.** In the course of 1829, he read separate papers on the vicinity of Bassano, and on the schist and fossil fishes of Seefeld; and again joined Professor Sedgwick in an elaborate examination of part of the Tyrol, the Bavarian Alps, and Styria; the fruits of which were, a map and description of the Austrian Alps; with other papers read in 1830 and 1831.†† In the latter year, Mr Murchison was chosen President of the Geological Society for the customary period of two years; and soon after

* Geol. Trans., 1st series, vol. i. p. 281.

+ Ibid. 2d series, vol. i. p. 317.

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Ibid. vol. ii. p. 237. To the references above given, we may add a paper On the Geology of the Malvern Hills,' by the late Mr W. Phillips-Thomson's Annals of Philosophy, (new series,) 1821, vol. i. p. 16, &c. And another paper with the same title, by the Rev. I. J. Conybeare.-Ibid. vol. iv. p. 237, &c., 1822.

Geol. Trans., 2d series, vol. ii. p. 293.

Ibid. vol. iii. p. 21.

Ibid. vol. iii. p. 128.

**"On the Excavation of Valleys:' Jameson's Ed. Journal, vol. vii. p. 15.- Tertiaries of the Cantal: Geol. Soc. Proc., vol. i. p. 140.Tertiaries of Aix-en-Provence: Jameson's Ed. Journal, vol. ii. p. 287, and Geol. Soc. Proc., vol. i. p. 150.

†† Geol. Trans., 2d series, vol. iii. p. 301,

wards read an account of some enquiries, by himself, on the secondary formations in different parts of Germany.

*

The extensive acquaintance which Mr Murchison had thus acquired with the rocks of various classes in different parts of Europe, and with the Huttonian principles, which we have elucidated in one of our recent numbers,+ was an excellent preparative for the task which he next undertook, in the complex region described in the present volume. His examination of the Silurian territory began in 1881, during the summer of which year he explored the borders of England and Wales; and there, he tells us—' The order ' of succession visible on the left bank of the Wye, between Hay ' in Herefordshire and Builth, where the old red sandstone is "seen distinctly to be succeeded by grey fossiliferous strata, 'first led me to expect that I had met with a part of the evidence ' required for a systematic study of the older formations,' (p. 5.) These rocks he followed on their line of bearing, to the neighbourhood of Ludlow and Wenlock; and at Aymestry he was so fortunate as to discover a most valuable ally in the Rev. Mr Lewis, who had already developed the structure of the district surrounding his own residence at that place. This gentleman, with Mr Aikin and Mr Greenough, whose map we have already mentioned, were the only persons who had made any advance towards determining the order of the groups, in the region now under consideration: this therefore seems to be the place for stating the nature of the assistance which the author derived from the two former geologists in this early stage of his enquiries.

MR AIKIN having long abandoned his intended survey of Shropshire, no sooner heard of the progress the author was making in the present work, than he placed at his disposal his original notes and drawings,' (p. 4.) These papers we have seen the geological drawings, the greater part by Mr Webster, with some by Mr Edmund Aikin, a brother of the possessor, form a large and very effective portion of the illustrations in the present volume; and the notes belong decidedly to a newer and better school than that of any observer who had preceded the writer in this enquiry. It is right to add, that Mr Aikin has frequently, with his well-known frankness, disclaimed any previous knowledge of the stratigraphic system described by Mr Murchison; and has always expressed his admiration of the energy and sagacity with which it was brought to light.

One of the general features in the structure of the country

*Geol. Soc. Proc., vol. i. p. 325, &c.
† Ed. Rev., vol. lxix. p. 440, et seq.

examined by Mr Aikin-which was more extensive than Mr Murchison seems to have supposed-was, as he believed, a want of conformity between the older (Cambrian) slates, which stretch out westward from beneath the lower secondary groups of England and the less inclined strata above them. The older slates he regarded as generally dipping towards the northwest at very high angles; while he supposed the newer and more fossiliferous groups, to rise slowly from south-east to north-west, reposing upon the slates unconformably. The fact, nevertheless, appears to us to be, that the lower secondary rocks also, are frequently much inclined in the Silurian region; and that their inclination is almost every where connected with plutonic disturbance, so that the dip is various in direction as well as in its angle. With this exception only, Mr Aikin's notes appear to us to coincide with Mr Murchison's descriptions in so many points of detail, that they must have been of great assistance in his enquiries. On looking over them, with the aid of the Ordnance maps, and of this Silurian volume, it now appears that, although the order of superposition was unknown to the writer, the same beds are so correctly identified at many distant points, both by lithological character and by fossils, as to enable a person possessed of the key to connect many of their detached portions. Thus, Mr Aikin recognized the Upper Ludlow Rocks' in the vicinity of the Abberley hills. He mentions the concretional structure which characterizes some of these beds. He distinguished the limestone of Yeo Edge and Mocktree Hill, by its quadrivalve shell,' (Pentamerus Knighti,) from what he calls the nodular limestones' of Wenlock and Benthal Edge; and connected several remoter calciferous rocks (the Caradoc' of Murchison) by their peculiar fossils, (Pentamerus lævis and oblongus,) to which he had given a temporary distinctive name; indicating, especially, the course of the ridges on the west of Wenlock Edge, from their containing those shells. In these notes we find, also, a line of plutonic elevation, precisely agreeing with that of Mr Murchison, traced for some miles south-west of Caer-Caradoc. And on the subject of compound sandstone,' the following question is proposed, which leads exactly to the views illustrated in this volume with great force of evidence:- - Is not the compound sandstone of Lythe Hill, &c., a mixture of grawackeslate with greenstone, formed during the deposit or outburst of 'the latter?'

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The REV. THOMAS TAYLOR LEWIS was, we believe, the only person who, previously to the author's enquiries, had determined the relations of any continuous portion of the stratigraphic series beneath the old red sandstone, on the double evidence of super

position and of fossil contents; and, as he communicated the results of his observations fully and freely to Mr Murchison, on his first coming to the vicinity of Aymestry in 1831, and subsequently co-operated with great zeal and effect in carrying on the examination of the country, the researches of this gentleman deserve a permanent place in the history of the subject.

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A member of Mr Lewis's family being engaged in the coal and ironworks at Titterstone Clee, in Shropshire, he had early opportunities of making himself familiar with the relations of the old red and carboniferous strata, at that remarkable point-where the coal is pierced through, and singularly capped with igneous masses, and supported at the height of from 1200 to 1700 feet above the sea by old red sandstone, which thence descends, rapidly, to the immediate vicinity of Ludlow, on the west. Mr Lewis had made collections of the rocks and fossils of these groups as early as 1824; and having previously attended the geological lectures at Cambridge, and paid some attention to the geometry of planes, on afterwards taking up Mr Conybeare's Outlines,' he became still better acquainted with the structure and relations of the strata by which he was surrounded. On removing in his clerical capacity to the parish of Aymestry in 1826, he soon began to apply his geological knowledge and his geometry to this new neighbourhood. We have had the pleasure of examining a part of that beautiful and instructive country under his guidance, and are thus enabled to give personal testimony to his exact acquaintance with its structure; and not less cordially to the frankness and absence of pretension with which his knowledge is communicated. And we are satisfied that Mr Lewis was the first person to ascertain that a series of what were called transition rocks, succeeds, conformably, to the old red sandstone at Ludlow; to distinguish the groups of strata respectively by many of their principal fossils; and to prove that in the tract immediately adjoining Aymestry, and on the south of Brindgwood Chase, the strata, though thrown up and much disturbed, exhibit every where the same determinate order of succession.

Not being a conchologist, it is probable that few of the shells which Mr Lewis thus discovered, were correctly named; but he was accurately acquainted with their forms and localities, and had disposed his specimens in drawers, keeping those of the successive strata apart, and distinguishing them by temporary names of his own;*—his method, in fact, thus far resembling that pursued by

*The following is an extract from a memorandum upon this subject, written by Mr Lewis himself, which is now before us :- My acquaint

William Smith in making out the succession of the strata near Bath. And at this time, it must be borne in mind, there were no Ordnance maps of Hereford and Shropshire to guide and connect geological enquiries.

Our readers will presently perceive that the four groups of strata thus determined by Mr Lewis, constitute, in fact, the Upper Silurian Rocks'-Aymestry being nearly in the focus of those rocks in England; and that their derangements are precisely similar to the disturbances since brought to light at Woolhope, and in other detached points, where portions of the Silurian strata appear within the boundary of the superior groups. He knew, also, that the next (inferior) group of strata, abounding in fossils, (now called Caradoc Sandstones,') rises conformably near Acton Scott-from beneath the die earth,' (now the Wenlock

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shale :') and, though not acquainted with the full value of his discoveries, he was quite aware that his groups formed the upper part of the transition series.' Mr Lewis had, therefore, at one time thought of publishing an account of the country in his vicinity; and we have felt it to be the more necessary to call attention to what he had done thus early; because, when afterwards more fully informed as to the novelty and importance of his observations, he cheerfully resigned the subject, rejoicing that it had fallen into the hands of a geologist whose practical knowledge was much greater than his own. It gives us great

ance with Aymestry commenced with my entering on the curacy of the parish in the autumn of 1826. Its natural beauties soon invited my attention, which was likewise directed to its natural and artificial sections, and its regular, but broken structure; and I began at once very zealously to collect the fossils, which were every where in abundance strewed over the roads and fields, and to dispose of them in drawers, keeping those of each stratum separate, and distinguishing the now named " ' upper and lower Ludlow rocks" by the name of "upper grauwacke and pendle," (the latter being the local name;) and the Aymestry and Wenlock limestones by Pentamerus, and coral or nodular limestone ;-the former from its abounding in the Pentamerus Knightii; and the latter from its great richness in corals, and the appearance which its weathered beds assumed in this neighbourhood, even where they were considered worth working for the kilns.

'I had very soon a collection, from most of the beds extending from the junction of the old red sandstone with the grauwacke, down to the Wenlock shale, (or nodular strata;) and had fairly traced these beds westward and eastward, to the full extent of this parish, in 1829; and along the prolongation of the Croft Ambrey and Gatley escarpements towards Ludlow; and in the outliers of Tinker's Hill and Caynham Camp, on the other side of the river Teme, in the direction of the Clee Hills; and likewise in the neighbourhood of Leintwardine.'

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