eee 
GEOLOGY. 13 
present valley-plain there was at least soft. of earth which has all 
been carried off. 
Between Bromley and Hayes portions of the valley are of 
difficult access, but Hayes Ford, which is on the high road, is an 
interesting point. 
The old river-gravel there lies in the meadows, etc., on either 
side of the road. On the western side a small stream called the 
Bourne flows in wet seasons. Another small stream comes down 
from the south-east in a ditch passing through meadows. ‘This is 
the overflow from the Keston ponds, which are fed by ‘‘ Czsar’s 
Pool” on Keston Common. The water from this source passes 
under the road through a pipe, and joins that of the Bourne. 
The gravel exposed at the large pit near Hayes railway station 
is a portion of a very large accumulation in that locality. This 
accumulation is attributable to the fact that two rivers formerly 
met there. Before tracing their direction, attention must be 
directed to the character of the deposit exposed in the pit. If this 
had lain in the direct channel of a swiftly flowing stream the 
material would have been separated and stratified, whereas it is a 
confused mixture of water-worn flints, which vary greatly in size, 
rolled Lower Tertiary pebbles, and silt. Some of the flints weigh 
as much as 18lbs., and large ones occur high up in the gravel. A 
- clear section shows about 1ft. of surface mould and raft. of gravel, 
which rests upon about 8ft. of white Thanet sand. Below the 
latter is the usual layer of green-coated unworn flints, resting 
upon the chalk. The elevation at the pit is about 21oft. About a 
quarter of a mile away, at Wickham Court, the Thanet sand is at 
the surface at 280ft. Allowing for the 8ft. of that formation still 
remaining at the pit we find that 62ft. of it has been carried away, 
as well as the whole of the superimposed Woolwich and Blackheath 
beds. The present surface elevation of the latter at the top of 
Coney Hill, West Wickham Common, near by, is 315ft. De- 
ducting 210ft., the elevation at the pit, it is seen that 1osft. has 
been removed. Having regard to the surface configuration of the 
locality, and the mixed-up nature of the materials forming the 
gravel, we think that the two rivers which met here fell into a 
small lake-basin, and that from the northern end of that lake the 
Ravensbourne issued and formed the valley which extends from 
Hayes Village to the foot of Bromley Hill. 
The existence of a lake-basin also accounts for the accumula- 
_ tion at the Hayes pit of numerous remains of extinct mammals, 
etc. Unfortunately the gravel does not contain the mineral matter 
necessary to effect perfect fossilisation. Consequently the bones, 
tusks and molar teeth which are frequently turned out are friable, 
and generally fall into fragments when exposed. In 1905 the 
workmen state that they turned out a bone as large as a big man’s 
body, which crumbled to fragments. This was probably the femur 
‘of a Mammoth, or Woolly Rhinoceros. On the 5th January, 1907, 
just as we reached the pit, the men came upon a fine Mammoth’s 
