62
THE INTER-RELATIONS OF
a view over a district formed of several geological formations. The
mass of the hill consists of London Clay, and accordingly on its
slopes oaks are the prevailing trees. The summit of the hill consists
of a capping of gravels on which grow beeches. In the valley to the
south, around the village of Pinner, there is an inlier of Woolwich
Beds, and on this area elms rise in stately groves. In the valley to
the north with alluvial deposits elms are again conspicuous, and on
the Chalk area beyond grow the well-known beeches of Cassiobury
Park.
Again, in the deep valleys of Somersetshire and Gloucestershire,
amongst the Cotteswold Hills, which are such beautiful examples of
valleys of erosion, the geology is distinctly marked out and indicated
by the vegetation. The bottoms on the Liassic clays are verdant
with rich grass meadows, a little higher at each side extends a stretch
of corn land coinciding with the outcrop of the Inferior Oolite.
Higher on the sides, rushes and other marsh plants indicate the ful-
ler's earth, which as an impervious argillaceous bed throws out the
water from the summit surface, and gives long lines of wet land.
Above this moist ground the Great Oolite forms the uppermost part
of the valley sides and gives elevated dry down-like land with sheep
pasturage.
Our chief apple and pear districts are on the Old or New Red
Sandstone or Devonian or Triassic rocks, and the excellence of the
cheese of Cheshire is attributed to the Triassic Marls of that county.
The suitability of one of the Oolitic formations to form corn-land
has given it the name "Cornbrash." This formation contains so large
a per-centage of phosphate of lime and produces such a friable and
suitable soil that it gives bushels of corn to the acre more than the
produce of land on any other formation.
The Weald Clay, too, was anciently covered so thickly with oaks
that the first geological name given to it was the Oak Tree Clay.
From the abundant oaks of this clay was produced the charcoal which
formed the fuel by which the famous Sussex iron was smelted from
the Wealden Iron-stones of the Wadhurst Clay two centuries ago.
Thus the geological structure of the Weald gave the ore and produced
the fuel by which it was worked, even as, though more directly, is now
the case in South Staffordshire, where the Coal Measures yield both
the iron ore and the coal for the smelting furnaces.
The association of pine woods with sandy districts is well known,
and is conspicuously seen not far from London in the Bagshot and