PRESTWICH — WOOLWICH AND READING SERIES. 79 



Of the connection existing at this period between the Hampshire 

 and London Tertiary districts there are few remaining traces : only 

 here and there on the broad chalk tract a hill higher than usual may 

 be found capped by some of the lower tertiary beds, which resume 

 their range in the London Tertiary district at Marlborough Forest. 

 The greater part of these fine woods are planted on a thin and irre- 

 gular capping of the clays and pebble beds* on the Chalk. The 

 tertiary strata here attain a height of 600 to 700 feet above the 

 level of the sea and form a narrow zone, which gradually expands 

 as it trends eastward and falls to a lower level. At a short distance 

 E.S.E. of this Forest the chalk attains, on the downs above Inkpen to 

 Highclerc, 'its greatest height, reaching at the former place an alti- 

 tude of 1 11 feet. The view from the fine open ridges of downs over the 

 well-wooded, broken, tertiary lowlands, which, commencing abruptly 

 at their base, stretches in an apparent plain far to the eastward, is one 

 of considerable beauty. In this part of the district the sands and 

 mottled clays form a large portion of the surface, and appear pecu- 

 liarly favourable to the growth of timber trees, x\t a short distance 

 further eastward the London Clay commences and the Bagshot Sands 

 almost immediately follow, the latter forming more open tracts of 

 heath and common. 



Along their northern boundary the "sands and mottled clays" rise 

 at a very gentle angle, and cover a considerable extent of ground on 

 the chalk hills to the north of Newbury, and thence by Pangboume, 

 Reading and Sonning to Twyford, Maidenhead, and Taplow, where 

 a further expansion of them forms the picturesque district known as 

 the Burnham Beeches. The chalk hills which bound the tertiary 

 area on the north, unlike the chalk of Salisbury Plains, present but a 

 small extent of open downs, and are well-wooded on their summits ; 

 this arises in part from a covering of clay drift and in part from thin 

 cappings of the lower tertiary beds, the latter being especially fre- 

 quent to the north and north-west of Reading, and again around Bea- 

 consfield, Penn, and Amersham. They are also found to some extent 

 near St. Albans, Welwyn, and to the north of Hertford, and between 

 "Ware and Bishop Stortford. Eastward of this latter place the mot- 

 tled clays are less important, and at the same time the lower ter- 

 tiaries become confined to a narrow belt, owing to which condition, 

 and the spread of the Boulder-clay drift over so much of North Essex, 

 these beds rarely present in this part of their course any mai'ked fea- 

 tures of surface. 



The southern outcrop of these strata, in consequence of the steep 

 angle at which they rise, is very narrow, — a feature persistently 

 maintained from the neighbourhood of Inkpen, by Kingsclere, Old 

 Basing, Farnham,and Guildford, to Croydon, along which line of coun- 

 try the "sands and mottled clays" form a belt generally from .50 to 200 

 yards broad, rarely exceeding a breadth of a quarter of a mile, and only 

 occasionally showing any discernible independent character of surface. 

 As this group, however, from its composite character of sands and 

 clays, presents a more yielding surface than the homogeneous mass of 

 * Including also a clay and gravel drift. 



