The universal geography : earth and its inhabitants

CHAPTER Y.
THE CHANNEL SLOPE.
DoRSETSniKE, WiLTSHIKE, HAMrSIIIKE, AND SuSSEX.
General Featlres.
HE region which, to the east of the Cornish peninsula, slopes down
to the Channel, is of considerable width only in its western portion,
where the Avon of Salisbury rises on the chalk downs of Wilt-
shire. Here its width is no less than 50 miles, but it narrows
as we proceed eastwards. The rivers become rivulets, and, on
reaching the neighbourhood of the Straits of Dover, there are merely combs down
which the water runs on the surface only after heavy rains. This region, never-
theless, is characterized by special features, due to its southern aspect, its deficiency
in navigable rivers, and its geological formation. In the latter respect some
portions of it bear a greater resemblance to France, from which it is now
separated bj' the sea, than to the remainder of England, of which it actually
forms part. The English "Weald and the French Boulonnais, or country around
Boulogne, are thus clearly the fragments of what was anciently a continuous tract
of land, whose severance has been effected by the erosive action of the sea.
The calcareous uplands which to the east of Devonshire form the watershed
between the Bristol and English Channels are generally known as the Dorset
Heights. They are of moderate elevation, none of the summits attaining a height
of 1,000 feet, but form bold cliffs along the coast. To geologists they have proved
a fertile field of exploration, for they exhibit very clearly the superposition of
various strata. The quarries of Lyme Regis have more especially acquired
celebrity on account of the ichthyosaurians and other gigantic reptiles of liassic
age which they have yielded. They are well known likewise to agriculturists,
for the coprolite, or fossilised guano, in which they abound contains a large
quantity of phosphoric acid, and furnishes a most powerful fertiliser.
The liassic rocks of Lyme Regis are succeeded in the east by oolite cliffs, which
terminate in the Bill of Portland, right out in the open sea. The so-called Isle
of Portland is in reality a peninsula rising superbly above a submarine plateau.