SUBTERRANEAN GEOLOGY OF SOUTH-EASTERN ENGLAND. 141
Sands, as we go southward, soon appear to undulate gently, and south
of Haywards Heath, dip steadily towards Brighton. We have now
crossed the centre of the anticlinal axis, and consequently soon find
the Hastings Sands disappearing beneath a belt of Weald clay on their
southern flank. The Lower Greensand then appears, forming but a
feeble ridge compared with that at Red Hill, and the southern outcrop
of the Chalk, the escarpment of the South Downs, is conspicuous in
front. The Gault plain is crossed, and in Clayton tunnel the Chalk.
It will be noticed that the Chalk at the southern end of the Clayton
tunnel is destitute of flints, which do not appear till Brighton is almost
reached, flint being found mainly in the upper beds of the Chalk, and
the dip of the Chalk being there towards the sea. It is thus evident
that in this Weald district the lowest beds are in the centre, and that
on travelling northward or southward from the middle of the Hastings
Sands we come upon higher and higher beds till we reach the North
or South Downs.
Sections such as are given in geological works across an anticlinal
axis like that of the Weald necessarily greatly exaggerate the heights
as compared with the horizontal distances, even when designed with
the utmost care. And those drawn so as to be clear and conspicu-
ous on the walls of a lecture room have the same unavoidable defect.
In the case of the Weald an explanation of its denudation once
current among geologists was based upon a monstrously exaggerated
section across it, appeal being made to this section and what it
involved as though it had been an exact transcript from Nature. But
though this exaggeration of height to length is more or less unavoid-
able in sections for books or lecture rooms, it often becomes a serious
hindrance to the student who expects to see in Nature appearances
resembling those shown in the sections of his Manual of Geology.
Consequently, to all persons who wish to have an accurate notion of
the true proportions of things in the Weald or elsewhere, the hori-
zontal sections of the Geological Survey cannot be too highly recom-
mended. One of these traverses the Weald from north to south, a
little east of, but nearly parallel with, the London and Brighton railway.
If instead of traversing the Weald district from north to south we
cross it from west to east, from Selborne to the sea, we find that the
lowest beds are towards its eastern boundary. In the neighbourhood
of Battle, a few miles north-west of Hastings, the Purbeck beds, the
highest of the Oolitic series, are here and there exposed in the middle
of the Hastings Sands district; and looking simply at the desirability