of the previous history of his subject, instead of the circumstantial series of dates and detail, which, in a work of such magnitude, is customary, and ought, we think, to precede the first account of every remarkable discovery."

The region is certainly delightful, both to the geologist and to all who rejoice in simple mountain scenery; and the task of making out its structure, and pursuing its various details, new, as for the greater part they were, not merely in local description, but to geology itself, must have been full of enjoyment. When the stratigraphic clue to the series of strata of which the country is composed had been once obtained, the varied phenomena, which before perplexed the enquirer, fell at once into their places, rewarding the discovery of the principle, by the almost spontaneous solution of difficulties that would otherwise have remained insurmountable.

6

One of the oldest enquirers, we believe, connected with the geology of this ancient region, is GEORGE OWEN of Henllys, in Pembrokeshire; who has been called the patriarch of English geologists. He lived during the reign of Elizabeth, and wrote, about 1595, a history of his native country; which, however, remained unpublished till 1799, when it was first printed in a volume of the Cambrian Register,'* the ancient style and orthography being very properly preserved. In one of his chapters on the natural helpes which is in the country to better the land,' the author mentions two vaynes of lymestone, running ' for the most part right east and west through Pembrokeshire,' which are evidently the carboniferous limestone, bounding the great Welsh coal deposit on the north and south. These beds he traces with great precision, considering the state of the subject when he wrote; and he mentions likewise, a third vayne of lymestone,' more northerly than the other two, which not improbably belongs to the Silurian System ;-distinguishing its qualities from those of the groups above mentioned, and tracing its course with such apparent accuracy, as to deserve the notice of those who examine the country, even at the present time.

6

6

A volume of 'Tracts in Natural History,' published in 1799, by Dr ROBERT TOWNSON, author of a book of Travels in Hungary,' and of an Essay on the Philosophy of Mineralogy,' contains some pages on the Mineralogy of Shropshire;' in which the occurrence of limestone with petrifactions, within the limits of the ancient territory now called Silurian, is frequently mentioned; and several localities of remarkable appearances are. indicated with apparent correctness-but without any thing that intimates an acquaintance with the importance of stratigraphic

* 8vo. London, 1799, vol. ii.

Feet

3000

2000

superposition, or of the connexion of the fossils with the order of the beds containing them. Dr Townson seems to have paid particular attention to the environs of Caer Caradoc; and he describes very correctly the ridges on the north-east of that hill, which now belong to the lower division of the Silurian rocks, under the name of Caradoc Sandstone.' 'If,' he says, 'from the Lawley and Caradoc we continue our course eastward, we 'find under both these hills, on their eastern side, a parallel range of white sandstone, which in some places has a very coarse grain. Where it is most regular, as under the Lawley, it presents its escarpement towards these hills, from which it is 'divided by a small valley, running parallel with the Wenlock Edge;'-and this latter ridge itself is then described as 'extending several miles in a continuous line, and inclining eastward.' One of the points principally deserving of notice in Dr Townson's 'sketch,' is the account of what he calls compound sandstone;' which, instead of being formed of grains of quartz ' alone, consists of very minute fragments of other kinds of stone; 'sometimes of an argillaceous or jaspideous nature, mixed with a 'few grains of felspar,' and belonging apparently to that class of rocks distinguished by Mr Murchison under the name of Volcanic Grits.

The year 1799 was remarkable in the Geology of England, for the production of WILLIAM SMITH'S Table of the Order of the 'Strata near Bath,' the basis of his subsequent Map and Sections; which, however, were not published till 1815; but the general diffusion of correct stratigraphical principles in this country, may be dated from the commencement of the present century, (1801,) when Smith first printed and distributed his Prospectus of a 'Delineation of the Strata of England and Wales.' When we reflect that we have reached only the fortieth year from that period when the very name geology was almost unknown in England, the progress of the science to its present condition does really excite surprise. It can be accounted for only by the peculiar

Snowdon

Snowdon Ra

ORDER OF THE STRATA FROM LONDON

and fortunate exposure of the numerous groups of strata which form the British islands-the spirit and intelligence employed upon our mines, and in the various commercial undertakings connected with the mineral structure and productions of our country -the facilities of intercourse every where to be found in England -and lastly, by the talents and devotion of the small number of persons who long since took up the subject of geology with the most enlightened views, and some of whom still continue to watch over its progress with unabated zeal. From these united causes, the steps in advance have been so numerous, and have succeeded each other so rapidly, that the history of this department of natural science, in England only, during the last thirty years, might, under different circumstances, have been diffused over a century. But our present business is with the more ancient strata alone, which occupy the border counties on the west of England, and in a great part of Wales.

About the close of 1809, MR AIKIN, one of the early members of the Geological Society, then recently established, (1807,) published proposals for a survey of Shropshire; and in the course of several succeeding summers had examined that county to a considerable extent, and caused several drawings to be made by Mr Webster; but the project was given up in 1815; and Mr Murchison has justly remarked, that at the early period when 'this task was undertaken it was almost hopeless; since that 'county not only contains every sedimentary formation, from the lias to the slates inclusive, but is also rendered most complex by the numberless dislocations of the strata, through the agency ' of volcanic rocks.'

Mr Aikin subsequently gave papers of great merit to the Geological Society,* on detached points of his intended survey; and we shall recur to his unpublished manuscripts, which were put into the hands of the author of the volume now under our examination.

The state of the subject when SMITH'S Geological Map of

Mark & Sandst. § Blue Marl

Oolites.

Clunch Clay

Chalk

Sand and Brick Earth

OXFORD

Uxbridge

* Geol. Trans., 1st Series, vols. i. iii. iv. and v.

1

England' appeared in 1815, may be judged of from the subjoined (reduced) section, by the author of the map, representing the succession of the strata from London to Snowdon; in which it will be perceived, that while the strata in the centre and east of England are subdivided in detail, the divisions on the west of the coal-tract are only two, and these of a very indefinite character. The MAP is defective in the same degree:—a large region, included under the terms Red-rhab Red-rhab and Dunstone' being all that separates the coal-tracts from the mountains of Wales; which are themselves disposed of under the terms killas, slate, and other strata. In the great map, nevertheless, and in a reduction of it published in 1820, a division is indicated which approaches to that of Mr Murchison; the Redrhab,' &c., above mentioned, surrounding the mountainous district in a somewhat crescent-shaped band, which extends from Aberconway on the north, to the extremity of Pembrokeshirein the same manner as Mr Murchison's Silurian district (No. 7,) surrounds the Cambrian (No. 8,) in our map above given in the second page. But when Smith's works are examined in detail, this resemblance will be found to be a very loose approximation, while the differences are many and important.

In the mean time the Transition Rocks,-to which terms a very vague signification was attached, became a sort of limbo for the reception of every thing that was ancient or obscure in the geology of England. But the general principles of stratigraphy were gradually making their way into practical application; and as fossils occasionally presented themselves from the older strata, of a new and singular character, suspicions began to arise that it might be practicable to find an order in the descending series also-although nobody had, at that time, the courage to grapple with the task of seeking for it. The publication of Mr Sowerby's Mineral Conchology,'-begun in 1812-was in this view of great usefulness; a register being thus opened for the reception of erratic specimens of shells, which were promptly made known, with the faithfulness of portraiture, for which the plates of that work have always been distinguished. One of the earliest numbers contained figures of the extraordinary genus Pentamerus, and gave the first representation of the species which characterize two prominent groups of the Silurian System. It is stated in the account of these fossils, that Mr Aikin had mentioned them to the author in 1812;—and that Mr Farey, also, -an original pupil of William Smith, and a sagacious observerhad sent several specimens from Croft Ambrey, near Aymestry, with remarks indicating a method of enquiry, which, if pursued, might probably have led him to correct notions of this part of the country.

The first important encroachment on the unknown tract béneath the old red sandstone, was made in MR GREENOUGH'S Geological Map,' published in 1819; a broad band, corresponding very nearly in position and extent with that of the Upper Silurian rocks, being there laid down as extending from Coalbrook Dale, on the north of the Severn, to the latitude of Ludlow; and identified, by its colour and place in the descriptive table, with the limestone groups of Dudley, Sedgeley, and Walsall-that of the Abberley and the Malvern Hills-and, less perfectly, with that which reaches from Woolhope to Mayhill, and occurs again, in a protruded outlier, on the wesk of Usk. The map is less correct in the south-west, from Ludlow to Caermarthen; but on the west of the latter place a continuous line, with the colours of the Dudley group, extends without interruption for some miles. These were very important identifications, and well deserving of an explanatory notice in the Memoir' which accompanied the map. But it is to be regretted that this paper was so brief as not to contain any description of the tract now referred to; so that here, as on many other subjects, the mass of valuable information accumulated in the author's notes has been lost to the public. Mr Greenough, however, has frequently expressed a conviction, as the result of his own observations in that country, that adequate enquiry alone was wanting to prove the existence of a succession of strata in the west of England, and in Wales-not less regular than that which had been demonstrated in the centre and east of the Island.

Messrs CONYBEARE and W. PHILLIPS'S Outlines,' published in 1822,* while it most essentially advanced geology in England, for some time diverted attention from the older rocks. The first and only volume published, comes down no farther than the coal formation; and in elucidating the upper portion of the secondary strata, it convinced the working geologists-whose number has been at all times small-that quite enough to give them occupation was still to be done, in reforming and completing the description of the more accessible portion of England: while it was obvious that the unknown region of the west required such labour and devotion, in order to effect any important result, as to deter those who had not leisure and other requisites at their full command.

The only modern writers mentioned by Mr Murchison, besides Mr Aikin, as having touched upon the geology of this part of England when he began to explore the country-are Mr Leonard Horner, in a memoir on the Mineralogy of the

*Outlines of the Geology of England and Wales.' 12mo. 1822.