318 THE CRETACEOUS ROCKS OF BRITAIN. 
Summary of Chemical Results. 
One of the chief features observable in the series of analyses of 
specimens of this zone given below is the gradual approach to uni¬ 
formity in the deposit throughout its range from the west of Eng¬ 
land to Hertfordshire, and it will be observed that the analyses 
do not show the marked differences which occur in the lower zone. 
Specimens from 
20ft to 70ft. below 
the zone of 
Bel. plena. 
Mupe 
Bay. 
20ft. 
below 
the Bel. 
Marls. 
Cerne 
60ft. 
below 
the Bel. 
Marls. 
Isle of 
W ight 
76ft. 
below 
the Bel. 
Marls. 
Dover 
70ft. 
below 
the Bel. 
Marls. 
Hitchin 
55ft. 
below 
the Bel. 
Marls. 
Hun¬ 
stanton 
15ft. 
from 
base of 
zone. 
Speeton 
(lj, 15ft. 
above 
Grey 
Bed. 
Speeton 
(2), 25ft. 
above 
Grey 
Bed. 
Per cent, of coarse 
residue 
•68 
•19 
•15 
•12 
•06 
•04 
•76 
•16 
Per cent, of fine 
residue 
10-67 
9-82 
7-07 
11-34 
9-13 
2-84 
12-24 
5*62 
Total per -cent, of 
residue 
11-35 
10-01 
7-22 
11 '46 
9-19 
2-88 
13-00 
5-78 
The Dover specimen contains the largest percentage of fine clay. 
In the Isle of Wight there must have been a rapid cessation of the 
influx of the clay noted in the underlying zone, the quantity de¬ 
creasing to 7J per cent. Similar conditions, however, obtain in 
Hertfordshire. To the north-eastward of Hertfordshire the Chalk 
becomes still more pure, and at Hunstanton there is little difference 
between this zone and the one below it. The Speeton specimens 
again show an increase, and the lower one contains more fine mud 
than any of the others. 
The percentage of coarse residue again shows progressive decrease 
from w r est to east. That of the South Dorset specimen still con¬ 
tains a larger percentage of free sand than any other, and both in 
this and the next above it sand-grains are conspicuously abun¬ 
dant, but at Dover and Hitchin the coarse residue is largely 
foraminiferal debris. The same remark applies to the Speeton 
specimens. The greater part of the coarse residues consist indeed 
of mineral particles, but they are the extremely minute grains which 
are selected by the arenaceous foraminifera for the formation of 
their tests and the debris of these usually forms the largest part of 
the coarse residue. 
In the next series selected the specimens are all taken as nearly 
as possible to the same horizon, just a few feet beneath the Belem- 
nite Marls, the summit of this zone. 
Specimens within 
6ft. of the Bel. Marls. 
Mupe 
Bay. 
Cerne. 
Dover. 
Hitchin, 
Herts. 
Hunstan¬ 
ton, Nor¬ 
folk. 
Louth, 
Lines. 
Speeton, 
Yorks. 
Per rent, of coarse 
•17 
•19 
•10 
•02 
•09 
•Oil 
•09 
residue. 
Per cent, of fine 
8-79 
9-82 
6-51 
3-56 
4-13 
1-678 
1-72 
residue. 
Total per cent, of 
residue. 
9-96 
10-01 
6-61 
3-58 
4 - 22 
1-689 
1-81 
