this native "rock." While the upper strata is soft and contains great
quantities of flints, the middle layers are brittle and yield plenty of
fossils, lower still is the marl, a greyish chalk of great value in the
fertilization of the gault. This latter forms an enormous moist ditch
or gutter at the foot of the escarpment, and from the farmer's point of
view is essentially bad land, requiring many tons of marl to be mixed
with it before this most difficult of all clays becomes fertile.
Between the chalk and the gault clay is a very narrow band of upper
greensand, only occasionally noticeable in the southern range, but
strongly marked in the North Downs.

"The chalk is our landscape and our proper habitation. The chalk gave
us our first refuge in war by permitting those vast encampments on the
summits. The chalk filtered our drink for us and built up our strong
bones; it was the height from the slopes of which our villages,
standing in a clear air, could watch the sea or the plain; we carved
it--when it was hard enough; it holds our first ornaments; our clear
streams run over it; the shapes and curves it takes and the kind of
close rough grass it bears (an especial grass for sheep) are the cloak
of our counties; its lonely breadths delight us when the white clouds
and the necks move over them together; where the waves break it into
cliffs, they are characteristic of our shores, and through its thin
coat of whitish mould go the thirsty roots of our three trees--the
beech, the holly, and the yew. For the clay and the sand might be
deserted or flooded and the South Country would still remain, but if
the Chalk Hills were taken away we might as well be in the Midlands."
(Hilaire Belloc: _The Old Road_.)

[Illustration: GEOLOGY OF THE DOWNS.]