posits was spread over the top of the chalk, certainly on
the strip between the South Downs and the sea, and probably over the
whole district between the Channel and the Thames valley: though in
this case, later denudation has proceeded so far that very few traces
of the Tertiary formations are preserved anywhere except in the greater
hollows.

Such being the original disposition of the strata which compose Sussex,
we have next to ask, What are the causes which have produced its
existing configuration? If the whole mass had merely been uplifted
straight out of the sea, we ought now to find the whole country a flat
and level table-land, covered over its entire surface with a uniform
coat of Tertiary deposits. On digging or boring below these, we ought
to come upon the chalk, and below the chalk again, with its cretaceous
congeners the greensand or the gault, we ought to meet the Weald clay
and the Hastings sand. Wherever a seaward cliff exhibited a section for
our observation, we ought to find these same strata all exposed in
regular order--the sandstone at the bottom, the clay above it, the
broad belt of chalk halfway up, and the Tertiary muds and rubbles at
the top. But in the county as we actually find it, we get a very
different state of things. Here, the surface at sea-level is composed
of London clay; there, a great mound of chalk rises into a swelling
down; and yonder, once more, a steep escarpment leads us down into a
broad lowland of the Weald. The causes which have led to this
arrangement of surface and conformation must now be considered with
necessary brevity.

The North and South Downs, with all the country between them, form part
of a great fold or outward bulge of the strata above enumerated, having
its centre about the middle line of the Forest Ridge. Imagine these
strata bent or pushed upward by an internal upheaving force acting
along that line, and you will get a rough picture of the original
circumstances which have led to the existing arrangement of the county.
You would then have, instead of a flat table-land, as supposed above, a
great curved mountain slope, with its centre on top of the Forest
Ridge. This gentle slope would rise from the sea between Chichester and
a point south of Beachy, would swell slowly upward till it reached a
height of two or three thousand feet at the Surrey border, and would
fall again gradually towards the Thames valley at London. On the
southern side of the Downs this