On the Af/ricidtural Geology of England and Wales. 477 



fragments, it contains more than is usually supposed. Dr. Man- 

 tell* speaks of beds of partially rolled flints as occurring not 

 only immediately beneath the turf, on the summits, and in some 

 of the valleys of the Downs, but also of beds of loam, clay, sand, 

 and gravel, and other debris, spread over the surface of the regu- 

 lar strata throughout the interior of the country, obscuring their 

 outcrop, and forming the immediate subsoil of the district — we 

 may add, of course, the soil also. The flints and gravel he refers 

 to the disintegration of the chalk ; the loam and clay to the 

 sands and clays of the Weald and the Forest ridge. He speaks 

 also of large IdIocIcs of siliceous sandstone, belonging to no regular 

 bed, now existing in the district, and of the ferruginous breccia of 

 the tertiary formations as occurring in these deposits; and he 

 designates a bed of broken and partially rolled chalk flints, rest- 

 ing on an eminence of Weald clay at Barecombe, as one of the 

 few examples of such detritus lying at a distance from the chalk 

 escarpment. 



Beds of waterworn fragments of sandstone and ironstone, derived 

 from the upper beds of the Hastings sands., are described as 

 covering the surface of the Weald clay and iron sand at Isfield, 

 Little Horsted, Barecombe, Wittingham, and Hamsey. We 

 have ourselves observed chalk flints within the Weald, in a cut- 

 ting on the Brighton Railway. 



With respect to Cornwall and Devon, it may be remarked that 

 the absence of erratic deposits from certain tracts by no means 

 proves that they were not submerged. In districts respecting 

 which there can be no doubt that they were beneath the erratic 

 sea, from detached portions of both upper and lower erratics still 

 remaining in them — as in some of the larger valleys of South 

 Wales — there are spaces covered with the reconstructed detritus 

 of the two brought down to lower levels, and other spaces quite 

 clear of all detritus. With these completely denuded spaces we 

 may compare those districts of England which are free from 

 erratic deposits, viewing the whole island as a district submerged 

 during the erratic period. 



Even in Devon and Cornwall, Sir H. De la Beche describes 

 transported gravel as occupying detached portions of the surface, 

 though he is doubtful to what portion of the tertiary era they are 

 to be referred. They indicate transportal from the north. 



Distribution of Soils, as laid doion by Agricultural Writers. — 

 Having closed the geological evidence respecting the presence of 

 erratic deposits over by far the greater portion of England and 

 Wales, we proceed to the agricultural evidence respecting varia- 

 tions of soil, which cannot be connected with variations in the 



* Geology of the South-East of England. 



