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THE CRETACEOUS ROCKS OF BRITAIN, 
E. The Chalk above the Totternhoe Stone. 
Above the horizon of the Totternhoe Stone, which over a large 
area marks the division of the two lower zones of the chalk, the 
true chalk may he said to commence, and the broad definition of it 
as a white soft limestone soiling the fingers will apply to the rock over 
a large extent of country. 
The chalk, however, is not yet quite a pure white except, perhaps, 
in the highest beds in some localities. In the south-east and south 
it is mainly white or whitish; in Wiltshire, Berkshire, Oxford¬ 
shire, Buckinghamshire, and Cambridgeshire, the lower part is 
greyish and the upper part white. In Norfolk the whole is whitish 
grey or white at the summit. This continues through Lincoln¬ 
shire and Yorkshire, though in the two latter counties the colour 
is curiously varied by pink bands. 
As a whole it appears as a firm blocky kind of chalk; in some 
cases where local circumstances have favoured induration by calcite 
there are beds of hard semicrystalline limestone. In Yorkshire 
most of the Lower Chalk is of a rough nodular character. 
As before, the details may be given under the following heads :— 
1. Microscopic Aspects. 
2. Examination of the Washings. 
3. Examination of the Residues. 
4 Tabulation of Results. 
5. Summary of Chemical Work. 
Microscopic Aspects. 
Devonshire and Dorset.—A large number of examples were ob¬ 
tained from the neighbourhood of Membury in Devonshire, and 
Cerne Abbas (North Dorset). In the lower part of this zone in 
the above named localities “ spheres " form an important feature 
in the rock, and may be estimated to form from 20 per cent, to 40 
per cent, of it; shell-fragments are never abundant, and form from 
5 to 10 per cent. more. Mineral grains of small size occur in 
nearly all specimens, but their proportion is very small indeed. 
Minute grains of glauconite also occur. 
About the middle of the zone and in the higher beds “ spheres ” 
are exceedingly numerous, forming in some instances 80 per cent, 
of the chalk. Shell-fragments are coarser but less abundant, and 
there is a decrease both in mineral and glauconitic grains, though 
both can be seen in nearly all samples. 
At Mupe Ba 3 q South Dorset, 20 feet below the Belemnite Marl 
(30) “ spheres ” constitute 70 pei* cent, of the rock, shell-fragments 
5 per cent., while mineral grains are more numerous and far larger 
than in North Dorset specimens. 
In none of the examples of this zone from Devon or Dorset do 
Foraminifera other than spheres play an important part; it is only 
here and there that a form which may be referred to Globigerma 
or to Textularia can be recognised. 
