On tiic AfjricuUiLral Geology of England and Wales. 485 



as (lerivino: benefit from clialkino", which has no effect on 1,2, 



. . . . ^ 



and 3; from its depth it is liable to be wet, but is capable, after 



chalking", of producing good wheat and a fine sample of barley. 



5. A fifth class is found on the brows and sides of the same 

 description of hills, contains less loam, and is mixed, very fre- 

 quently, with dry, harsh sand, and small gravel. It is a warm 

 subsoil, producing early vegetation, and is applied generally to 

 the culture of wheat, turnips, barley, and artificial grasses. Of 

 the higher part of the chalk district generally, he says that it has 

 the appearance of a level plain, broken into many irregular parts, 

 and intersected by deep hollows, through which the streams take 

 their course. Considerable tracts of meadow and pasture are 

 found along the valleys in which these flow. In them the greater 

 portion of the population is congregated. These alluvial tracts 

 consist of alluvial soil or moor, on a strong calcareous loam, some- 

 times covered with sand, or fine gravel, or large bodies of peat. 

 It is observed that in proportion as the moory covering is com- 

 bined with the alluvial sediment, is its capacity for improvement. 

 To these varieties he adds the strong flinty loams, and hazel 

 loam, covering the chalk of Portsdown Hill, and resting in the 

 islands and low ground frequently on clay. The varieties of soil 

 on the chalk of the Isle of Wight are described as the same as in 

 the other parts of Hampshire. The author lays down two dis- 

 tricts of sand and gravel in Hampshire. That on the south con- 

 sists of the eocene tertiaries of the New Forest, that on the east of 

 the green sand strata of Woolmer and Alice Holt Forests. He 

 found great difficulty in determining the exact boundary between 

 these and the chalk district, by reason of the numerous veins of 

 sand and gravel, and bodies of clay, loam, marl, and brick-earth, 

 and. declares it to be impossible without a particular examination 

 of each field. We can, from experience, bear testimony to the 

 difficulty of doing this, even with such an examination, without 

 digging and boring, when the junction of the chalk and tertiaries. 

 takes place on a flat or a long slope. 



With respect to his southern forest tract we have already shown 

 that the variations of its soils depend, except on abrupt escarp- 

 ments, on the covering of flint gravel, and the depth and composi- 

 tion of the warp " upon that gravel, more than upon the mineral 

 variations of the strata. The place of those strata in the series, 

 long imperfectly understood, has lately been cleared up in a satis- 

 factory manner by Mr. Prestwich.* On geological maps they have 

 hitherto been marked as upper marine, London clay, and plastic 

 clay. The upper marine is nothing more than a deep bed of 

 erratic flint gravel, not confined to the area there laid down, but 



* Quarterly Journal Geo!. Soc, vol. iii. p, 355. 



