132 PRIMAEVAL MAN IN THE VALLEY OF THE LEA.
The extreme left of the section shows Stoke Newington Common,
eighty-five feet above the Ordnance datum (with the Hackney Brook,
whose surface before it was recently obliterated, was sixty-eight feet
above the Ordnance datum), dropping into the Lea Valley, the
surface of the river on this line being twenty feet above the Ordnance
datum. On the right the section gradually rises to the Leyton side
of the Lea, crossing the Fillibrook stream. The stream at this part
(which, too, will soon be obliterated), is forty-four feet above the
Ordnance datum, and the adjoining Moyer's Lane is fifty-six
feet.
The diagonal shading at the bottom of the section shows the
London clay ; the vertical shading above indicates the gravel. The
heavy black line on the top of the gravel shows the line of the
"Palaeolithic Floor" on both sides of the Lea, and the uppermost
line shows the line of "warp and trail," surmounted by humus.
Undoubtedly the "Palaeolithic Floor," and the "warp and trail"
at one time extended right over the Valley of the Lea, as indicated
by the heavy dotted line and the fine line above. At the time when
the Palaeolithic men lived on this "floor," the river was probably
some twenty feet higher than now, as shown on dotted lines above
"R. Lea"; the valley at that time, therefore, was much flatter and
more marshy, and being flat, the river of necessity was constantly
changing its bed. The excavation of the last twenty feet of the Lea
Valley has been made since the "warp and trail" was deposited over
the "Palaeolithic Floor." Very little denudation has, however, taken
place in recent times ; for Roman remains and even Neolithic Celts
have been found in the alluvial flats at D D.
At the points A and B, the "warp and trail" has been denuded
off the "Palaeolithic Floor," and at these special points the "floor"
crops up on the surface. At these positions, therefore, perfectly
unabraded Palaeolithic implements and flakes (which have never been
moved, unless in agricultural operations), may be found on the surface
as the Palaeolithic implements of chert are now found at Bois du
Rocher, near Dinan, in Brittany. It must, therefore, never be too hastily
assumed that because Palaeolithic implements are sometimes found
in an unabraded state on a modern land surface, that they were actually
made upon the humus as we now see it. The surroundings of every
such position should be carefully noted. At the point C, and at
other well defined distant points from the Lea and Thames, the thin
stratum identified as the "Palaeolithic Floor" ceases. The men had