24
NOTES ON DRIFT MAPS,
him to expect them. But let him, on the other hand, start from the
Thames northward, and he will find that his geological guide soon
begins to fail him utterly. He will not, indeed, find much to complain of
in Essex or south of Aldborough, inasmuch as the rocks on the Essex
and the southern part of the Suffolk coast consist chiefly of London
Clay, Red Crag, and Alluvium, all which formations are recognised
on non-drift maps. North of Aldborough, however, the traveller
would expect to find chalk cliffs, with hardly a break, thence to the
Wash, but would discover, to his astonishment, that the cliffs at
Southwold, Lowestoft, and Yarmouth are composed of sand, gravel,
and clay of some kind. At Yarmouth he might learn that the top
of the chalk was reached in a well at the depth of five hundred and
twenty-six feet below the surface, which is there, as most people know,
but a very few feet above the level of the sea. Proceeding northward,
he would, after crossing some low ground, and passing some cliffs
with much-blown sand banked up against them, but all composed
of soft materials, arrive at Happisburgh, no chalk whatever having
been seen so far. From Happisburgh to Weybourne the nature of
the sea cliffs is admirably shown in Mr. Clement Reid's sheet of
continuous sections between those places, published two or three
years ago by the Geological Survey authorities. From it we learn
that nowhere between Happisburgh and Cromer does the chalk
appear in the cliffs except at Trimingham, though its top cannot be
many feet below their base. And at Trimingham the chalk appears
only in the shape of two bosses of no great size, about half a mile
apart from each other; the result apparently of contortions in that
formation which have forced it above its ordinary level at those two
points. West of Cromer the chalk becomes more or less visible on
the foreshore, and as Weybourne is approached it is seen to form
the base of the cliff. Here and there, along the portion of coast
illustrated by this section, as at Trimingham and Cromer, the cliffs
reach a height of 200 ft. or more. Sometimes on the foreshore only,
sometimes also forming the base of the cliff, a band of Pliocene Beds
appears. The section being drawn to a true scale, the cliff at the
Lighthouse Hills, Cromer, may be seen to be composed of about
6 ft. of Pliocene Beds, surmounted by more than 200 ft. of Glacial
Drift; at Trimingham, of 4 or 5 ft. of Pliocene and 190 ft. of Drift,
or thereabouts. And a glance at the section generally will suggest
the notion that to a person seeking information as to the geology, or
the agricultural capabilities of northern Norfolk, or as to its advantages