222 Mr, G. J. Hinde’s Notes on the 
that is, they have no streams or currents of water flowing down 
them. Very little surface erosion is now taking place on the 
slopes of these dry chalk valleys, for the rain, however heavy it 
may fall, is at once practically all absorbed by the chalk, and 
none is left to form streams or transport the gravels which now 
cover the lower portion of the valleys. ven when the Bourne 
is flowing, as at the present time, its current is insufficient to 
effect any appreciable erosion, or move the gravels down the 
very gradual incline of the present valley. 
Passing now to a consideration of the gravels in the respective 
valleys of the chalk, the most important on the eastern side of 
the drainage area is that in which Caterham is situated. This 
valley extends through the chalk escarpment at a pass, about 
560 ft. O.D., overlooking Godstone, in the valley of the Gault, 
260 ft. below. On either side of the pass, the chalk hills are at 
levels of 700-750 ft. A tributary valley starts from near the 
edge of the escarpment at the south end of Marden Park at a 
level of 623 ft., and reinforced by other valleys coming from the 
high ground (850 ft. above O. D.) near Woldingham, it joins with 
the main Caterham valley at Marden Lodge at a level of 347 ft. 
Near the junction of the two valleys gravel appears to be present, 
judging from the stony character of the lower slopes, but there 
are no sections shown, and the Bourne also here makes its first 
appearance in the valley. Below Marden Park the Caterham 
valley continues without any important tributary till it joins the 
Smitham Bottom valley at Foxley Hatch, close to Purley Station, 
at 218 ft. above O.D. Its length is about five and a half miles, 
or reckoning from the head of its longest tributary, six and a 
half miles. 
At Whiteleaf, gravels are worked at the bottom of this valley 
on the east side of the main road to Caterham, at levels of 
310 ft. Sections show a thickness of 10 to 15 ft. resting on an 
uneven surface of white chalk. The gravel consists of an 
agglomeration of tightly packed stones with a few boulders, in a 
brownish-grey, marly matrix of the same character from top to 
bottom, and without any traces of stratification. The coarser 
materials are, for the most part, of blunted, subangular chalk 
flints, but little worn, with the usual flint sponges and echino- 
derms. Tertiary flint-pebbles are fairly common, as also 
flattened and rounded fragments of iron sandstone; one piece 
of this measured 7X5 x2 in. Besides these, rounded and 
elongate boulders of pebble-conglomerate of various sizes are 
not uncommon; the rounded from 6 to 12 in. in diameter, the 
elongate specimens in one instance 14 x 10 x 6 in., in another 
17 x 14x 7in., and the face of a third still firmly embedded 
in the gravel was 283 x13in. The pebbles in some of these 
boulders are cemented by ferruginous material, in others the 
