12 BOROUGH OF LEWISHAM. 
Bromley Hill, which forms the eastern border of the valley rises 
to 200ft.; on the western border at Beckenham the pebble gravel 
of the Blackheath beds rises to 180ft. A thickness of at least 120ft. 
which once overlaid the valley-plain has therefore been swept away 
by the river. The average width of the valley-plain for a length 
of one mile is a quarter of a mile. By cubing these dimensions 
it will be found that the quantity of material removed per mile has 
been 27,878,400 cubic yards, representing as many tons in weight, 
and this is exclusive of the quantity removed from the slopes on 
either side. 
Throughout the valley, from the foot of Bromley Hill to the 
foot of Westerham Hill, at Cudham, the eastern side rises more or 
less steeply, while the western side presents a gentle slope. 
The geological formation is the same on both sides, and 
we were at a loss to account for the difference in the inclines until 
the discovery of a terrace-gravel, high up on the western slope 
opposite Bromley, proved that the river first ran on that side, and 
afterwards cut its way towards the eastern side. Its final bed, 
while it still remained a river of considerable volume, was close to 
the eastern side of the valley. Therefore the deserted western side 
has had some thousands of years more weathering, which has 
toned down the original steepness of the slope. 
In the lower part of the Bromley Recreation Ground, near 
Shortlands railway station, there was, until quite recent years, a 
small pit exposing the river-gravel, but the local authorities, 
influenced by esthetic considerations, have had it filled in, and 
turfed over. 
In ascending to the highest point of the Recreation Ground 
the steepness of the slope will be noticed, and at the top the fine 
view of the valley in both directions will be admired. In the road 
outside the lower south-eastern corner of the ground there is a 
notice board indicating a footpath leading to Pickhurst Green. By 
following this, and crossing the railway by a footbridge, a meadow 
is entered with a footpath leading up to the top of the valley. 
Close to the exit from the footpath is a small disused gravel pit. 
The bank at the back of the pit discloses a section made up of 
about 4ft. of sandy brick-earth, resting upon a stratum of river- 
gravel, about a foot thick, which again was laid down upon the 
pebble-gravel of the Blackheath beds. Both sides of the pit 
should be examined, and at some seasons it is necessary to 
scrape away the herbage and sand to obtain a good view of the 
section. 
The river-gravel here exposed is 25ft. higher than the valley- 
plain, and about a third of a mile. distant from the present 
attenuated stream where it runs through the Recreation Ground. 
To appreciate the denudation which has occurred since the 
river flowed at this high point, it is necessary to bear in mind that 
it was then the bottom of a valley. Supposing the banks of that 
valley formed a slope similar to the present one, then over the 
