28
THE SHALLOW AND DEEP WELL WATERS OF ESSEX.
position of the well when the Memoir was published, and has consequently placed
the explanatory words "Valley Drift," against the details of the superficial brick-
earth and gravel. But he informs me that he has since discovered that the true
locality of the well-section is not Dagenham but Dagnams, between three and four
miles north-east of Romford. The very great thickness of London Clay given as
existing at Dagenham, together with the round numbers "400 feet," seemed to
me, last July, to suggest a want of perfect accuracy in the account. But as the
words " Valley Drift " applied to the superficial beds at Dagenham, and are
utterly inapplicable to those at Dagnams, which are more than 200 feet above
the sea, and as 200 feet of London Clay would have been enough for my purpose,
I thought I might safely quote this well-section. However, though it cannot be
mentioned as confirming the existence of the continuation of the long line of
synclinal fold spoken of in my little paper, nothing else there seems to me to
need any modification.—T. V, Holmes, February 23rd, 1893.
Rainfall at Chelmsford in 1892.—Mr. F. Chancellor has recorded the
following monthly summaries of the rainfall at Chelmsford as observed by
himself during 1892 :—January, 0-48; February, 2-42; March, 1-08; April,
rat; May, 0-87; June, 2-64; July, 1-27; August, 3-52; September, 2-22;
October, 4-05; November, 2-09; December, 1-31; Total, 23-16.
THE SHALLOW AND DEEP WELL WATERS
OF ESSEX.
By JOHN C. THRESH, D.Sc., M.B., D.P.H. etc.
[Read, February 21st, 1893.
CONTENTS.—Sources of our Water Supplies—Variation in the character of
the water from various kinds of Gravel—Effect of a stratum of Boulder
Clay—Magnesian Waters—Deep well waters (1) from Tertiary Sands
(2) from the Chalk—Great variation in character—Causes—Effect of
proximity to the Ocean, etc.
The paper is written in the hope that Essex Geologists may le able to explain some of
the author's difficulties, and that others may help by procuring for him samples
from certain districts not yet represented.
THE above somewhat hurriedly adopted title is probably not the
most appropriate one for the subject we have to discuss this
evening, and on that account our secretary acted wisely in giving my
short syllabus in the circular convening this meeting.
During the past three and a-half years I find that I have
examined 874 samples of water from various portions of Essex
(by far the largest majority from the district around Maldon and
Chelmsford), the object, in every case, being to ascertain whether
they were sufficiently free from pollution and otherwise of such a
character as to be fit for drinking and domestic purposes. About
two years ago, I published a "Report on the Water Supplies of the