46 
TERTIARY FORMATIONS. 
clear idea of their geological relations, it wdll there- 
fore be necessary to take a brief view of the extent, 
and characters, of that depression of the chalk. 
The district comprehended by the Isle of Wight 
basin, is about 100 miles in length, and at its 
greatest breadth does not exceed twenty miles. 
Tlie southern side is formed by the highly inclined 
chalk, extending from the Culver Cliffs, at the 
east end of the Isle of Wight, to White Nose, in 
Dorsetshire, five miles west of Lulworth ; the north 
side by the South Downs, that pass from Beachy 
Head, to Dorchester, in Dorsetshire. The strata 
of which these liills are composed, dip generally 
from 15° to 5° to the south ; the inclination vary- 
ing in different places. The south side of the 
basin must therefore have been extremely steep, 
while the slope of the north side was very gentle. 
The western margin cannot be distinctly traced, 
and the eastern is now entirely destroyed, the sea 
flowing through the opening.* 
The annexed sketch will illustrate this descrip- 
tion, and show the connection between the out- 
lying fragments of these beds in Sussex, with those 
of the Isle of Wight. 
* Mr. Webster on the Strata overlaying the Chalk, Geolog. Trans, 
vol. ii. p. 170. etseq. 
