572 Reviews— Whitaker's Geology of London. 
the flints and earthy matter, together with clayey and loamy material 
washed from Tertiary strata. 
The author makes many references to the terms Glacial, post- 
Glacial and pre-Glacial. The two latter terms (as he says) are 
inadmissible into schemes of classification from their having no 
definite significance; but they are conveniently used when our 
knowledge is very limited that is to say, when we find a bed that 
is older than Boulder-clay, and which cannot be definitely proved to 
be Pliocene; or when we find a bed that is newer than Boulder-clay, 
and yet not definitely Recent. As Mr. Whitaker remarks (p. 328), 
*“« Beds which are truly post-Glacial in a southern district, may be of 
the same age as others which are clearly Glacial in a northern one ;” 
and these remarks apply to the Pleistocene Thames Valley Deposits. 
We are glad to find that the author supports the view of the 
fluviatile origin of the Thames Valley gravels and brick-earths. The 
organic remains indeed clearly support this contention. The diffi- 
culties raised have béen based on the mode of occurrence of the 
deposits; but it must be borne in mind that the greater part of the 
gravel is simply re-deposited Glacial gravel, ready made, and not, 
perhaps, transported any great distances by the river. In the 
course of the accumulation of the river-drifts, the river has deepened 
its channel, leaving terraces in some places at different levels ; 
but there is no marked regularity in these terraces as we trace the 
course of the Thames Valley deposits from Maidenhead to London. 
Following the account of the River Drift, we have a chapter on 
Alluvium, etc. We should have preferred to divide these subjects 
into Pleistocene and Recent Alluvial Deposits. It is true that, in 
the area described, the Alluvium is distinguished from the “ River 
Drifts” by its fineness of texture, but that is a local feature, for in 
the higher courses of the Thames and its tributaries we find a good 
deal of Recent gravel; and Alluvium itself seems entitled to be 
called ‘River Drift,” as much as the brick-earth and gravel of 
Pleistocene age. Instructive sections are given of the Alluvium 
shown in making the Tilbury Docks and in other places. 
Chapters devoted to Physical Geology and to Keonomic Geology, 
etc., complete the first volume, and we may call especial attention to 
the remarks on Springs, Wells, and Water-supply. It is impossible 
here to enumerate all the matters of interest discussed in the volume, 
suffice it to say that no subject seems to have been neglected. The 
work is illustrated by many sections and some pictorial views, and 
with figures of flint-implements. Lists of fossils are also given. 
A small coloured index-map would have been useful, but we ought 
not to make the slightest complaint when we have such a wealth of 
information in two volumes, bound in cloth, for a total cost of eleven 
shillings! That London geology excites a good deal of scientific 
interest apart from its practical bearings, is shown by the large sale 
of Mr. Whitaker’s Guide to the Geology of London, of which (we 
understand) a fifth edition has just gone to press, and this is an 
excellent introduction to the subject treated so fully in the volumes 
before us. 
