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NOTES ON ESSEX GEOLOGY.
of the silted-up channel of an ancient stream-course," and
he thought "that the contents of this old silted-up channel
had been very largely derived from the Boulder Clay."
At a later date, when I had the pleasure of being with him,
we found, in another part of the cutting, a mass of Boulder Clay
on "the same level as that at Hornchurch and similarly covered
by gravel belonging to the Thames Valley system."
The author concluded that the Boulder Clay of Hornchurch
and Romford, beneath the old River Gravel belongs "to some
drainage-system more ancient than that of the present Thames,"
and he concludes that in the valleys of the Roding, near Romford,
and of the Blackwater and its tributaries, around Chelmsford
and Maldon "we have evidence of their excavation, to some ex-
tent, before the deposition of the Boulder Clay." As that
evidence consists of the occurrence of Boulder Clay at com-
paratively low levels in places, I feel bound to say that I am not
greatly impressed by it. The Boulder Clay so generally rests
in a very uneven manner on underlying beds that one is almost
bound to find it at a low level in some part of any valley that cuts
through it. At the same time I am ready to allow that many
of our valleys were started in pre Boulder Clay times.
1896.
F. W. Harmer, in treating of the Pliocene beds of Holland
and their relation to the English and Belgian Crags, refers at
some length to the Walton Crag, and gives a list of Mollusca
found in it, and in the Scaldisian and Poederlian of Belgium.
The conclusion he comes to is that the two Belgian deposits "are
equivalent to the Walton stage of the Red Crag, and not to the
whole of that formation," as had been supposed.10
Dr. A. E. Salter's paper on Pebbly Gravel11 is of a general
character. Our Essex examples come in under all the five types
into which he divides the High Level Gravels of the Thames
Valley (based on the constitution of the beds), and then those
of N.E. Essex and of Essex Naze, are separately treated. I
must own to some difficulty in following the author's somewhat
complex arrangement.
10 Quart. Journ. Geol. Soc., Vol. lii, pp. 754-758.
11 Proc. Geol. Assoc., Vol. xiv., pt 8, p. 389.