THE ANALYST. MEMOIR ON THE GEOLOGY OF THE VALE OF (Read before the Worcestershire Natural History Society, March 13, 1834.) Ar the request of several members of the Society, I have been induced to draw up an account of the geology of that part of the county of Worcester with which from personal residence I was best acquainted; an investigation which was the more desirable as this district does not appear to have been hitherto very minutely examined by the geologist. Before I proceed to examine the subterranean structure of the Vale of Evesham, I will give a short sketch of its more obvious and superficial characters. This district is bounded on the E. by the lofty escarpment of the Cotteswold Range, and on the S. by Dumbleton and Bredon Hills, which constitute outliers of the same geological structure as the Cotteswolds, with which they have doubtless at some period been continuous. To the N. and W. this district has no natural boundaries, and might without impropriety be extended over nearly all Worcestershire, which is in fact one vast vale, of which the S. E. angle is denominated the Vale of Evesham. The Vale of Evesham has an undulating surface, and, in some parts of it, hills occur of considerable steepness, and from 200 to 300 feet in height. These hills, however, by no means render the term vale inapplicable to the district, since from the lofty heights of Broadway and Bredon those minor elevations are barely distinguishable from the plain. From its low and sheltered position the average temperature of the district is high, and hence in a great measure, arises the fertility for which it has been perhaps too highly celebrated. In some parts of the district, indeed, tracts of very good land occur. This is chiefly the case where the surface consists of red marl, diluvial sand, or the alluvial deposits of the Avon. But where the lias clays come to the surface without any foreign admixture, as is the case over a large portion of the district we are considering, a wet tenacious soil is the result, requiring great labour and attention on the part of the farmer, and often rewarding him with very inferior crops. It would seem, indeed, that the lias is better suited for garden-ground than for agriculture. Near Evesham and Pershore are some extensive and valuable February, 1835.-VOL. II. NO. VII. B market gardens, in which the lias clays, by a high degree of manuring and cultivation, are rendered very productive. The whole drainage of the Vale of Evesham falls by a variety of small brooks and watercourses into the Avon. This river, though immortalized by the poets, has little to recommend it in the eyes of the painter. The clayey soil through which it flows imparts a considerable degree of muddiness to its waters at all seasons, and being kept by means of locks nearly on a level with the surrounding meadows, it loses all the picturesque effect which its neighbour the Severn derives from the steepness of its banks. From being kept constantly full, a moderate quantity of rain suffices to cause a rapid overflow, but as the water seldom remains on the land many hours before it subsides, it deposits but a small portion of the silt which it holds in suspension. The Avon is commonly flanked on one or both sides by extensive meadows, whose level surface proves them to result from alluvial deposition. These meadows produce heavy crops of hay, which, from its excellent quality, bears generally the highest price in the market. The bed of the Avon is for the most part deep, with a muddy bottom, with a few exceptions where beds of gravel occur. Its ordinary depth is from 12 to 20 feet, and its breadth from 30 to 50 yards. Having thus given a sketch of the external features of the Vale of Evesham, we will proceed to examine its internal structure. In so doing it will be most convenient to begin with the highest stratum in the district, and proceed in geological order to the lowest. We shall thus investigate in succession the following formations-inferior oolite, upper lias shale, marlestone, lower lias shale, and new red sandstone. The Inferior Oolite occupies the brow of Ilmingdon and Broadway Hills, and extends thence with great regularity along the brow of the Cotteswolds, into Gloucestershire and Somersetshire. It also forms a cap on the summit of Meon Hill, and of that magnificent outlier Bredon Hill, where it rises gradually towards the W. and N. to the height of about 900 feet above the level of the sea, and may be conveniently examined near the summer-house, which forms a conspicuous landmark to the surrounding country. On Broadway Hill it reaches the height of 1,086 feet, and forms the surface of that elevated table-land. This hill, as well as the whole of the Cotteswold Range, has lately been very carefully surveyed by Mr. Lonsdale, Secretary to the Geological Society, to whose labours those may be referred who wish for further information respecting that district. The Inferior Oolite is quarried at Bourton-on-the-Hill, and in many other places, as a building stone, for which it is well suited. In appearance it has so close a resemblance to the Great Oolite that in many cases it can only be identified by examining its geological position ;-the mineralogical characters of both formations being the same. It commonly consists of a yellowish limestone, in which the "ova" or small globular particles from which it takes its name, are more or less numerous and regular in different specimens. On Bredon Hill, portions of this stone sometimes occur of a brick-red colour, owing probably to the presence of an oxyde of iron. On Bredon Hill the Inferior Oolite appears at some period to have been much disturbed; in the various quarries its strata are seen greatly shattered, and dipping in all directions, often with a high angle of inclination. These dislocations are doubtless of great antiquity, as the present outline of the surface does not seem to be affected by them. The general dip of the Oolite of Bredon Hill is to the S., and hence it descends with a gradual inclination much lower down on that side than on the N., where it terminates suddenly in a bold escarpment. In many parts of England this formation contains an abundance of fossils, but they seem to be comparatively rare in those portions of it which abut on the Vale of Evesham. There has, however, been no scarcity of animal life in the period of its deposit, for a great part of the Oolite is composed of fragments of shells and corals, but it is rare to find these remains in a sufficiently perfect state to fit them for cabinet specimens. The most numerous shells are those of the genus Terebratula. These researches, which have been chiefly confined to Bredon Hill, have as yet produced only the following fossils : Ammonita 1 species; Terebratula 5; Trigonia 1; Pecten 2; Cidaris 1; Pentacrinus 1; Terebellaria 1; Flustra 1; Sarcinula 1. Nine genera, 14 species. The The next succeeding formation is the Upper Lias Shale. traces of this formation in our district are so imperfect that in many places its existence is rather to be inferred from analogy than proved from ocular evidence. Nevertheless, as there are some places where it certainly exists, it would be improper to omit this stratum in our list, especially as in the North of England it assumes a very important character, both in a geological and commercial point of view. In this and the adjoining counties, the stratum is vastly reduced in thickness, and there are no inducements for the speculator to penetrate its interior, and hence illustrative sections of it are rarely to be met with. Mr. Lonsdale states that he has met with it in many parts of Gloucestershire, and on his authority I have coloured it in the Society's Map, along the side of Broadway and Ilmingdon Hills, where it may be looked for at about three quarters of the way up. It occupies a similar situation in Bredon Hill, and may be traced round the N. side from the height above Aston-under-Hill to Wooller's Hill, its situation being commonly marked by a grassy slope, below the steep brow caused by the Inferior Oolite, and above the line of the Marlestone quarries. Numerous springs are thrown out along the line of its course, as is always the case where clay interstratifies with more porous strata. This formation being in this district much concealed by grass and vegetable soil, but few fossils have as yet been found in it, but |