Oil the Agriadtural Geology of England and Wales. 483 



to indicate the four natural divisions of the county, viz. the Vale 

 of the White Horse Hills, a continuation of the chalk district of 

 the Chilterns, the valley of the Kennet, and the Forest. 



The chalk hills are described as running through the centre 

 of the county, from Ashbury on the W., to Shealley on the 

 E., where the Thames flows through a gorge in the chalk. The 

 more western parts, from their abruptness towards the Vale of 

 White Horse, and from their general deficiency of soil, are de- 

 scribed as unfit for cultivation, but affording excellent sheep 

 pasture : surface a blackish light earth on chalk. This down- 

 district terminates with Isley Down on the E. The south sides 

 of the chalk hills towards the Vale of Kennet afford, according 

 to the same authority, some intermediate tracts of considerable 

 fertility, consisting of flints, chalk, loam, and gravel, but almost 

 wholly on a chalky substratum, which extends on both sides of 

 the Lambourn towards Hungerford, and, keeping at an irregular 

 distance from the line of the Kennet, winds round to meet the 

 Thames as far as Cookham. We have now reached the great 

 central area of the chalk — its patria as Pennant called it — on 

 which all the branches of chalk hills conver<re. In this district, 

 which constitutes the elevated platform of Marlborough Downs, 

 Salisbury Plain, and the Hampshire Hills, the chalk attains its 

 greatest elevation in England, being 1011 feet above the sea at 

 Inkpen Beacon. The Report on Wiltshire is by Mr. Davis, 

 of Longleat, a celebrated land agent, the same who, on hearing 

 Smith's explanation of the connexion between the course of 

 agriculture pursued on the Wiltshire hills and vales, and 

 their geological structure, exclaimed, That is the only way 

 to learn the true value of land." The soil of this county," 

 he says, " though various, is, to a certain degree, uniform. The 

 hills are chalk, with its usual accompaniment of flint ; and in 

 general the land on the sides of the hills, from which the flints 

 have been washed, is a chalky loam, or rather dissolved chalk. 

 In the valleys through which the rivers run are beds of broken 

 flints, covered with the black earth washed from the sides of the 

 hills above." Hence we may observe that the white land prevails 

 near the sources of the rivulets, where the hills are steepest, and 

 the flinty loams near the junction of the hills, where the land is 

 flattest. The sides of the hills where they have been most 

 washed have the thinnest and weakest soil, and the tops of the 

 hills, which have been little if at all washed, have frequently the 

 strongest and deepest land. 



From this it appears that in this elevated region, above the 

 limits to which the lower erratic tertiaries usually extend, and at 

 about two-thirds of that elevation which we have estimated as the 

 limit of the upper erratics in the north, there are traces of a thin 



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