28 
DILUVIAL DEPOSITS. 
tains rounded masses of chalk, blocks of crystal- 
lised carbonate of lime, sometimes stalagmitical, 
ferruginous breccia, scoriaceous ironstone, a coarse 
grit containing angular fragments of quartz, and 
flattened oval pebbles of siliceous sandstone. The 
flints are more or less broken, have suffered but 
little from attrition, and are so abundant as to 
form a constant supply for repairing the roads in 
the south-eastern part of Sussex. This bed has 
clearly been formed by the destruction of the upper 
portion of the chalk ; and it is equally evident, 
that the cause which produced the disintegration 
of the superior strata, was as transient as it was 
effective ; since, although the chalk in vdiich the 
flints were imbedded has been entirely destroyed, 
the latter have sustained but very little injury, and 
must have been elevated above the reach of the 
waters so soon as the chalk which had invested 
them was worn away. 
Descending into the valleys, accumulations of 
chalk rubble and ochraceous clay are again seen 
lying upon the basseting edges of the solid strata ; 
and the slopes of the hills are generally composed 
of similar materials. Examples of this kind occur 
in almost every locality of the South Downs. 
The gravel-pits (as they are called) of Barcombe 
are part of a ridge of broken chalk flints, slightly 
rolled, resting upon an eminence of the Weald clay. 
Tlie flints are of various shades of yellow, brown, 
and carnelian. The colour, which in all probability 
results partly from decomposition, and jiartly from 
an impregnation of metallic oxides, pervades the 
substance of the flint, but is much paler towards 
