126 The Agricultural Relations of the Western Portion 
with superficial deposits along tlie greater portion of the valley, 
except in Hengistbury Head and St. Catherine's Hill. 
Tlie Lower Bagshot series commences on the western side of 
the Avon valley, and extends to within two miles of Doixhester. 
Between the termination of tliese strata and the chalk a narrow 
band intervenes, consisting of the Lower Eocenes, or London and 
plastic clays. In their range, westward from the Isle of Wiglit, 
these have thinned off considerably, and have lost much of their 
argillaceous cliaracter. The London clay too, which is generally 
full of fossils, has ceased to be fossiliferous. The area occupied 
by the Lower Eocenes is very irregular, varying in width with 
the amount of disturbance by which the chalk has been affected, 
from less than 200 yards to nearly 2 miles. 
The white clay, worked so extensively between Poole and 
Corfe Castle, is not a member of tlie plastic or mottled clay 
series, but occurs in irregular beds just above it, in the lower 
part of the Lower Bagshot sands. 
Characters of tlie Soils on the different Strata when free from 
transported matter. — These different members of the Eocene 
tertiaries yield, when their surface is exposed, soils of very 
different characters. They are covered, however, through a 
great portion of the district, by other more recent deposits, 
which are disregarded on geological maps, but which modify 
considerably the agricultural characters of the strata on which 
they rest. 
We will first consider these characters in the uncovered state 
of the strata as they occur among broken ground and on steep 
escarpments. Under these conditions the Upper Eocenes, or 
freshwater clays and marls, yield cold and wet soils, capable how- 
ever of considerable improvement by draining and good cultiva- 
tion. The characters of the Upper and Lower Bagshot strata 
are, under similar circumstances, nearly alike, producing coarse 
and loose siliceous sands, which in some cases have an absorbent, 
in others a retentive base, as they happen to rest upon beds of 
sand or clay. Strong soils are however seldom of great extent 
on these strata. The greater portion of the country \i'hic:h they 
occupy consists of wide-spreading sandy wastes, covered with 
heath and furze, their dreariness partially relieved by extensive 
plantations of pine and fir. The fir tribe, liowever, have often 
been planted where a little geological examination might have 
taught the planters that the oak would flourish. At a depth 
below the surface accessible to the tap-root of the oak, beds of 
clay and sandy clay frequently occur. To a practised eye their 
existence becomes evident before they are cxiiibited in sections, 
by the vigorous growth of the oak when it has become acci- 
dentally established among the firs. 
