230 ON THE LEA VALLEY.
plateaux and at the same time filled up more or less completely
the Pre-Glacial valleys. In the Boulder-clay at Hornchurch
near Romford, about 100 feet below its usual level, thereabouts,
yet covered by some of the oldest gravel of the present Thames
there is a certain approximation to coincidence, in the valleys of
the two periods. Where Post-Glacial drainage has taken a new
course, the position of an old Pre-Glacial valley may remain un-
suspected but for a well boring, as at Newport Grammar School.
Where there is a local coincidence between the Pre-Glacial and
Post-Glacial valleys, there we may find a fragment of a Pre-
Glacial channel filled with material of Glacial age beneath river-
deposits of later date, as at Littlebury and the Lockwood
Reservoir. But of course both channels alike suggest that
during their formation the whole country stood at a much higher
level above the sea than it now does. For in each case the
bottom of the channel is below the present level of the sea.
The photograph is one taken by Mr. F. Meeson during the
visit of the Geologists' Association in April, 1901. The spectator
is looking southward, and the view gives the section across two