32
NOTES ON DRIFT MAPS.
a drift map of his district, in a county like Essex, must be indispen-
sable not merely to the geologist but to the botanist or entomologist
who may wish to know what spots are likely to yield particular kinds
of insects or plants. And outside the ranks of the students of Nature,
drift maps cannot fail to be useful and interesting to every intelligent
person, both in connection with the practical advantages and disad-
vantages of certain sites for buildings, well-sinking, or some agricul-
tural purpose, or, as showing at a glance, why certain tracts of country
are, or have been, centres of population, while in others only scattered
farmhouses or tiny hamlets can be seen.
Appendix—Essex Memoirs of the Geological Survey.
It may be useful to mention that the Memoirs of the Geological
Survey, dealing wholly or partly with Essex, are the following :—
The Geology of the London Basin (vol. iv. 1872, pp. 631, price
13s.) by W. Whitaker, with notes by H. W. Bristow, T. McKenny
Hughes, and others. The authors describe the Chalk and Eocene
beds of Essex, in the neighbourhood of Billericay, Brentwood,
Chelmsford, Chipping Ongar, Epping, Ingatestone, Maldon, Ray-
leigh, Rochford, Romford, and Waltham Abbey.
The Memoir on Sheet 47 is by W. Whitaker, W. H. Penning, W.
H. Dalton, and F. J. Bennett. It treats of all the formations mapped
in sheet 47, including the Glacial deposits. (pp. 98, price 3s. 6d.,
1878.)
The Memoir on Quarter Sheet 48 S. W. is by W. H. Dalton, edited
by W. Whitaker. All the formations met with are described. They
consist of the Eocene, Pliocene, Glacial, Post Glacial, and Recent
beds of the neighbourhoods of Colchester and Mersea. (pp. 24,
price 1s., 1880.)
The Memoir on Quarter Sheet 48 S. E. is by W. Whitaker. It
treats of all the formations in 48 S.E. and in the adjoining part of
48 N.E., which is south of the Stour, or, in other words, within the
boundary of Essex. (pp. 32, price 9d., 1877.)
The Memoir on Quarter Sheets 48 N. W. & N. E. is by W.
Whitaker, with notes by W. H. Dalton and F. J. Bennett. The
country described is chiefly in Suffolk, but a narrow strip of Essex,
south of the Stour, and mostly west of Manningtree, is included.
The details of some east Essex well-sections obtained since the other
memoirs on sheet 48 were published, and properly belonging to them
as regards locality, are here inserted. And it contains a valuable list
of 345 works on the geology and palaeontology of Suffolk. (pp. 163,
price 2s, 1885.)
The Guide to the Geology of London and its neighbourhood, by W.
Whitaker, i; a general explanation of the large map of "London and