570 Reviews — Whitaker's Geology of London. 
Special interest is usually concentrated on debateable subjects, 
and although certain differences of opinion are maintained on the 
classification of some of the Hocene divisions, there is little dispute 
about the position of the beds; the literature of London geology has 
increased most largely by the discussion of the Thames Valley 
deposits and their relation to the Glacial epoch. More recently the 
subject of underground geology has aroused a great deal of attention, 
for the deeper borings have proved the presence of rocks not pre- 
viously suspected to occur beneath the area. 
Special interest may therefore be said to be divided between the 
Underground Geology and the Pleistocene Geology. 
The former is becoming more and more a practical subject. 
Speculations on the behaviour of rocks, especially of Paleeozoic 
rocks beneath thick accumulations of Secondary strata, are neces- 
sarily hazardous. Were the whole of the West of England smothered 
up with Chalk and London Clay (the South Wales Coal-field being 
exposed), we might know nothing of the Bristol Coal-field, if several 
deep borings had proved simply Old Red Sandstone in some places 
and Silurian rocks in others. This up to the present time has been 
practically the result of deep borings under the London area. 
Mr. Whitaker gives a full account of all that has been previously 
written on the plain of older rocks that lies under London. He is 
careful to point out that there is no evidence of a ridge beneath the 
area, though it would seem there may be something of the sort 
northwards, for the older rocks come nearer the surface at Ware 
than they do beneath London or Harwich. 
On the subject of most commercial importance he concludes 
(p. 46) “that Coal-Measures are likely to occur somewhere along 
the line of the Thames Valley, or in neighbouring tracts; and that 
those Coal-Measures are likely to yield workable coal. It is rash to 
attempt to foretell the future; but it seems to me that the day will 
come when coal will be worked in the South-east of England.” 
The new boring at Streatham has given further particulars of the 
presence of the Great Oolite Series beneath the London area, and 
a full account of this important boring is now for the first time 
published. 
By the aid of the many borings, Mr. Whitaker is enabled to dis- 
cuss’ the underground range of the Jurassic and Cretaceous rocks, 
and it is somewhat remarkable to learn that there is no certain 
record of Lower Greensand in the area, though it must underlie the 
Gault near Risborough. From the Gault there is a gradual passage 
through the Upper Greensand to the Chalk; and this is an interest- 
ing fact when we remember that chalky conditions commenced in 
Gault times at Hunstanton. 
In the description of the Cretaceous beds, the author acknowledges 
help from Mr. Jukes-Browne, and some modifications are made in 
the classification of the zones and rock-beds of the Chalk. Thus the 
Chalk Rock is assigned an independent position between Middle and 
Upper Chalk ; the zone of Belemnitella plena is separated from the 
Melbourn Rock and put with the Lower Chalk; while the lowest 
