26 
THE ANTIQUITY OF MAN 
HioH tvATizif e-7Tfr 
30 feet below the marsh level — can be traced a thick 
layer of peat, strewn with the trunks of great trees, all 
of them uprooted ; not one is to be seen standing as it 
grew on the ancient land surface. They represent, we 
suppose, the crop of trees which flourished when the 
backwaters of the Thames first invaded the forests which 
grew on its banks. Below the marsh deposit and the 
peat is a thick stratum of ballast gravel — water-rolled 
stones, many of which are of considerable size, deposited 
in the river bed when the 
Thames was a powerful, 
rapid stream. In places, 
the ballast gravel is so 
thick that its deepest 
layer lies 60 or 80 feet 
below the present bed of 
the river. The bottom 
layer of the ballast gravel 
marks the time when the 
land had reached its 
highest point of eleva- 
tion, and the estuary of 
the river reached its 
furthest limit in the 
North Sea. 
The trench just de- 
scribed gives us a section 
across the floor of the 
valley of the Thames, five miles below the central part 
of London. To ascertain the kind of people who lived 
in England when the old land surface was clad with a 
flourishing forest, we have to go down the river still 
further, to Tilbury docks, situated on the marshland 
on the north bank of the river, twenty miles below 
London. When these docks were being made in 1883, 
the old land surface — the Neolithic valley bottom — was 
met with at a depth of 32 feet below the level of the 
marsh, 36^ feet below the limit reached by the water at 
high tide. Three feet beneath that old land surface was 
MARSH mVER 
= CLAY-^-^Z=:_^Z=^-_^_— ^ 
':/'-''. 7:fy-''"'/^^ _-_— 
I6'8 
18 5 
/,}^*^y°/'///v':',/,''//,'^^ - _-_- 
MUD i PEAT H 
23-» 
Z708 
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■/'■■^^^'-'■■■- ■ ■ ■■■VV^. -_-. 
310S 
3-».05 
r° •''^'^^ ^^r.a^,rH ^ooo N^ 
; ^0''^'- BALLAb 1 .TA V E L • -i^' '~^ '-■--. - -. 
Fig. 12. — Diagram to show the various strata 
which buried the old land surface and the 
human skeleton at Tilbury. 
