278 
Farming of Buckinf/licaitshire. 
constitutes the principal masses of a well-defined range of hills 
resting on the Oxford clay. These hills are continued, in a 
south-west course, to Brill, but the range here is traversed and 
extensively broken by numerous broad valleys, and thus separated 
into insulated patches. Throughout that part of the county the 
Portland stone forms the central region of the hills, the ironsand 
being confined to the summit. In the valley or plain to the south 
of Aylesbury, which separates those hills from the chalk range, 
the mass of the lower greensand can be little seen. In most maps 
it is made to extend all over Cublington, Aston Abbotts, and 
Wing, to Bierton. It forms no prominent feature in any of these 
parishes, and only appears in thin veins of yellowish sand, or 
may be more generally discovered in the rich superficial deposits 
which cover the best pastures, and give a little friability to some 
of the arable land. A trace of it can be discovered at Kingsey 
and Towersey, but the geology of this tract is much concealed by 
the extensive debris of flint-gravel. The sand and sandstone, 
which are particularly well developed in the Leighton cutting of 
the North- Western Railway, are entirely silicious, and contain 
brown oxide of iron, so that the tract occupied by this formation 
strikes the eye by the reddish-brown nature of the soil. The 
sandstones are often formed of coarse conglomerates, and consist 
of granulated pebbles embedded in a ferruginous silicious cement. 
The sand and stone occasionally alternate^with subordinate beds 
of clay, loam, and ochre, which latter was much dug at Brill, but 
the supply appears now quite exhausted. The soil is mostly a 
sandy loam, inclined to be weak, with patches of clayey loam, 
gravel, and peat ; but all with fair farming produces good crops, 
and is mostly famous stock land. The lower greensand, at its 
conjunction with a more retentive stratum, throws up many 
springs, and the chalybeate spring at Dorton takes its rise in this 
formation. 
The chalk and greensands which have been under considera- 
tion compose the first division of the secondary strata, called by 
geologists the cretaceous system ; the rest that will be treated 
of belong to the oolitic or Jurassic system. 
Before arriving at the great clay district of Buckinghamshire 
the Portland or Aylesbury oolite claims our attention, and is 
perhaps the most interesting geological feature of the county. 
The first appearance of the Portland stone, on the Oxfordshire 
side, is at Towersey, and it is afterwards largely developed from 
Haddenham to Cuddington, and is found all over the high 
ground, which is traversed by the turnpike from Thame to 
Aylesbury. Beyond that town this southern vein wears out, 
and its place seems to be supplied by the ironsand, so that these 
