Reviews: Whitaker— Geology of London, &c. 
and Watford, the Memoir has to deal 
with—I. The Cretaceous Series, con- 
sisting of—l. Lower Greensand, ob- 
scurely recognized, however, by the 
boring of the Hampstead Well; 2. Gault 
(probably 200 feet thick) ; 8. Upper 
Greensand (about 70 feet thick under 
London); 4. Lower or flint-less Chalk 
(400 or 500 feet); 5. Chalk-rock (one 
or more peculiar, thin, hard, fossiliferous 
bands, that Mr. Whitaker has described 
in this Memoir and elsewhere); and, 6. 
Upper Chalk (about 300 feet): also local 
patches of ‘Reconstructed Chalk,’ and 
of ‘Clay-with-flints.’ The former must 
have been re-arranged before the laying 
down of the ‘Reading Beds;’ but the 
latter (noticed also under the same 
name* by M. E. Hébert as occurring 
in Picardy) Mr. Whitaker thinks may 
be of several different ages, having 
been, and perhaps now being, formed by 
dissolution of the Chalk by percolating 
waters.—II. Of the Eocene Series, we 
have—l. The Thanet Sand (found in 
London wells to vary from 13 to 44 
feet), which soon thins out westward, but 
is thicker to the east. 2. The Woolwich 
and Reading Beds (from 25 to 90 feet), 
occupying along the strike, and in very 
numerous outliers,t a considerable area 
in ‘Sheet 7. 8 The London Clay 
(ranging from 380 to 440 feet in thick- 
ness near London, thicker to the E. and 
thinning to the W.) is, of course, an 
important feature in the geology of the 
London district; and with its revised 
and augmented lists of fossils,f (even 
* L’Argile a Silex; see Grou. Mag. vol.i. p. 120. 
{~ This is, of course, a word in frequent use in 
the Memoir; and so is the word ‘ Inlier,’ as ap- 
plied to a limited area of lower strata exposed 
by a local denudation of upper strata. Mr. Jukes 
(in his ‘ Manual,’ 2nd edit.) uses this word dif- 
ferently, namely, for a particular bed intercalated 
among other beds. The former use of the word, ~ 
however, not only seems very appropriate, but 
is older, having been introduced in a Geological 
Survey Memoir before 1861. It is the ‘Outlier- 
by-protrusion’ of Mr. Martin. 
{ For the vicinity of London only. The vo- 
lume of the Palzeontographical Society’s Mono- 
graphs, lately published, adds to their number. 
VOM. eNO. VEL. EF 
n2 
{ 
= = (is 
eater across the London Basin from North to South, showing the probable ridge of Old Rocks under London. 
Diagram- 
a. Lower Bagshot Sand. 
b. London Clay. 
patches of Wealden, Purbeck, and Port- 
land Beds. 
wx Ridge of Older Rocks. 
** Approximate Sea-level. 
i. Lower Greensand. 
k. Wealden Beds (on the South). 
e. Chalk with flints. 
65 
1. Oolitic Clays (on the North), with 
f. Chalk without flints. 
Gault. 
g. Upper Greensand. 
h. 
c. Woolwich and Reading Beds. 
d. Thanet Sand. 
