Outlines of the geology of England and Wales. With an introductory compendium of the general principles of that science, and comparative views of the structure of foreign countries ... / By the Rev. W.D. Conybeare ... and William Phillips ... Part I.

  • Conybeare, William Daniel, 1787-1857.
Date:
1822
Catalogue details

Licence: Public Domain Mark

Credit: Outlines of the geology of England and Wales. With an introductory compendium of the general principles of that science, and comparative views of the structure of foreign countries ... / By the Rev. W.D. Conybeare ... and William Phillips ... Part I. Source: Wellcome Collection.

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    passes to the south-west, and at Royston downs assumes the character of a range of hills, the escarpment of which con- tinues with little interruption, and in the same direction, by Baldock and Hitchin in Herts, Dunstable in Bedfordshire, and Tring and Wendover in Buckinghamshire to Goring in Oxfordshire, a distance of about 75 miles, where it is broken through by the valley of the Thames. (G. Map.) This range,* in passing through Buckinghamshire and Oxfordshire, is well known under the name of the Chiltern hills, in Bedfordshire the names of Royston and Luton Downs are applied to different parts of it: its average breadth is from 15 to 20 miles : from the summit of its north-western escarpment it declines gra- dually to the south-east, where its strata dip beneath the upper bed of the London basin ; it is furrowed by many trans- vease vallies of which several break entirely through it; such are that through which the proposed line of the London and Cambridge Canal passes that of the Grand Junction Canal; but the principal opening through the chain, is that through which the Thames flows from Goring to Maidenhead, and which constitutes the most striking and picturesque scenery on the banks of the principal river of the island. On the west of the Thames, the chain is continued, bearing the name of Ilsey Downs and the Whitehorse hills, to Marlborough Downs, where it is broken through by the valley of the Kennet; which, like most of the rivers flowing through this formation, rises iii the subjacent and older stratum, and breaks entirely through the elevated chain of the chalky downs. This valley separates the northern Marlborough Downs from the long ridge oil the south of Marlborough, which stretches westwards to Bagdon hill about three miles north-west of Devizes in Wilts. On the south-east, this ridge, skirting round the vale of Pewsey (a broad opening between the chalk ranges, exhibiting the inferior strata), connects itself with the northern point of that extensive cretaceous district which occupies all the north of Hampshire and most of the south of Wiltshire; its longest diameter from east to west, being more than 50 miles; its shortest from north to south, about twenty. This vast area has been appropriately denominated by Pen- nant, the great central Patria of the Chalk ; the centre and source whence all the ranges of this rock traversing the island diverge. The following points will assign its limits with sufficient pre- cision for our present purpose. On the east, the hills above * The remainder of the description of this range and extent of the chalk ^sby the Rev. W. D. Conybeare.