THE GEOLOGY OF SOUTH ESSEX. 215
to the engineer, Sir J. W. Bazalgette. Essex well-sections and trial-
borings fill more than forty pages, many of them being new both to
readers of the earlier memoir and to those of the publications of the
Essex Field Club. In addition to the borings of the Metropolitan
Board, the geology of London and its suburbs is illustrated by a very
large number of sections seen here and there in the streets and roads,
together with some taken along the course of the Metropolitan and
Metropolitan District Railways. Mr. Whitaker quotes from a paper
by Mr. B. Baker, describing the strata passed through by these
railways, many interesting details. However, there is only space
here to state that in some places the "made ground" was very thick,
being occasionally as much as 24 ft. At Westminster it was found
to a depth of 18 ft. It is very gratifying to find that so many details
of sections now wholly invisible have been preserved and published.
Dr. A. Geikie, Director-General of the Geological Survey, makes the
following remarks, in his preface to the memoir, on the preservation
of the details of sections :—
" It is only by the co-operation of many independent workers that
the details of the numerous fresh sections that are continually being
opened can be secured and recorded before they are destroyed or
concealed. Such co-operation is rendered much more effective by
the various Field Clubs and Societies now established round London,
and it is hoped that henceforth no section of importance will be laid
open and covered up again without being carefully noted by local
observers. The Geological Survey will thankfully receive any such
notes which these observers may be willing to communicate, with a
view to incorporation in any subsequent edition of this work."
To these observations I will only add a word of caution to the inex-
perienced geologist to beware of chronicling "made ground" as one
of Nature's formations. However, no one with good eyesight and
common-sense can go wrong who accurately describes what he sees,
and where he sees it, and sends his account to our esteemed honorary
member, Mr. Whitaker, at 28, Jermyn Street, London, S.W.
To return to Vol. I. After a short chapter dealing with the physical
geography of the district and giving a brief description of the various
formations to be seen within it, come two in which we have an
account of the subterranean plain of rocks older than any at the
surface, which the evidence of deep borings has shown to exist under
London and its neighbourhood. It may be remembered that this
subject formed the topic of my Presidential Address to the Essex
Field Club in January, 1888. Since that paper was written the boring