UPPER CHALK. 
73 
rapid view of the characters and distribution of 
these deposits, premising that the white chalk 
forms the Downs ; the argillaceous and arenaceous 
strata emerging from their base along their north- 
ern escarpment, and constituting the low banks 
and terraces of the district which intervenes be- 
tween the sand and the chalk hills, except in the 
west of Sussex, where the Shanklin sands rise into 
hills, equal in altitude to the neighbouring chalk. 
I. Chalk with flint. 
From the situation occupied by this division of 
the chalk, it has suffered most extensively from 
the effects of those catastrojihes to which we have 
already alluded. In almost every part of the in- 
terior of the country, its ruins may be seen in the 
form of beds of gravel, or partially rolled flints. 
What its original thickness may have been, cannot 
be ascertained ; but the occurrence of large blocks 
of stalagmites and stalactites on the summits of the 
highest hills proves that chalk caverns formerly 
existed above the most elevated points of the South 
Downs. 
The chalk of this subdivision is generally of a 
purer white, and of a softer texture, than the in- 
ferior strata ; but in other respects, presents no 
sensible difference. It is regularly stratified, and 
partakes of the general inclination of the other di- 
visions of the series. It is separated by horizontal 
The strata of Sussex thus constitute three grand formations ; viz. 
1 St, Partly freshwater and partly marine. The strata above the chalk. 
2cl, Marine. The Chalk and Shanklin sand inclusive. 
3d, Freshwater. The Weald clay, Hastings sands, and Ashburn- 
ham beds. 
