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THE LIBRARY TABLE.
of old ones. He was also one of the most active members of the Epping
Forest Museum Committee, and contributed to the Chingford Museum a
small collection of rock specimens from the gravels of the Forest and of fossils
from the Boulder Clay towards its northern border. He will be much missed
by all who knew him, not merely on account of his scientific ability and
energy, but as one of the most kindly, considerate, modest and sincere of
men. T.V.H.
THE LIBRARY TABLE.
Report on the Water Supply of the County of Essex. By Dr. J. C.
Thresh, County Medical Officer of Health, &c. Pp. xv, 168; 12 plates.
8vo., Chelmsford, n.d. [1901.]
It is many years since Dr. Thresh, who had already made his mark in
scientific literature, brought his trained abilities to Essex, and several most
valuable reports and other works have since appeared from his indefatigable
pen. That before us is a compendium of information, indispensable to all who
would study the question of the supply of that prime necessity of life, potable
water, to the inhabitants of our county.
The work opens with a brief geological summary of the several water-
yielding formations and associated impervious strata occurring in Essex,
followed by a classification of their products as (1) Surface-waters, (2) River-
waters, (3) Subsoil-waters, and (4) Deep-well-waters. The first are promptly
condemned as all more or less contaminated with manurial or other organic
substances, and occasionally with mineral ingredients such as sulphate of
magnesia, derived from the surface-soil. River-waters have this objectionable
feature modified by partial oxidation of the organic matter, but require further
purification by filtering, at least for domestic purposes. Subsoil-waters,
extensively used for isolated houses, hamlets and villages, are notoriously
liable to similar or worse contamination. Unfortunately, such are utilized
for the partial or entire supply of Witham, Clacton, and even Chelmsford. It
may be remarked in passing that the hydrogen sulphide present in the water
of newly-made wells in the Boulder Clay originates in the alteration of the
iron-pyrites abundant in that clay. It is of but temporary formation, and
harmless, though offensive whilst its production continue. Belief in the
medical efficiency of such waters is not yet wholly extinct.
Deep-well waters, as the only satisfactory source of large supply, neces-
sarily occupy the bulk of the report. The inter-communication of the waters
of the Tertiary sands and of the underlying Chalk has been fully established,
and probably the progressive deterioration by sea-water of the supply from
the Chalk-wells of the Essex and Suffolk coasts is due, not to actual outcrop of
the Chalk in the sea-bed (though it crosses the estuary at Grays), but to
connection of the Lower Tertiary sands with those of the North Sea, where the
London Clay has been removed. The many wells now drawing upon the
Chalk, to an extent exceeding the supply from Kent and Cambridgeshire,
induce a flow of sea-water to make up the deficiency.
Nevertheless, until the development of the Essex coalfields makes it worth
while to convey water from other counties more richly endowed therewith,
the Chalk constitutes the only available source for large supplies, and the