Ch. XIII.] 
CRAG OF ENGLAND. 
173 
are in great part horizontal, or slightly undulating ; but at 
some points they are much disturbed, especially where several 
masses of chalk appear to have been protruded from below. 
The annexed section may give a general idea of the manner 
in which the crag may be supposed to rest on the chalk as we 
pass from the Norfolk cliffs, at Trimmingham, into the interior, 
where the country rises gradually. 
No. 30. 
E 
a, Chalk. b } Crag. c, Lacustrine deposit. 
D, Trimmingham beacon. E, Interior and higher parts of Norfolk *. 
The outline of the surface of the subjacent chalk, in this 
section, is imaginary, but is such as might explain the relations 
of those protruded masses, three of which appear in the cliffs 
near Trimmingham, and which some geologists have too hastily 
assumed to be unconnected with the great mass of chalk below. 
We shall treat of these presently, when we describe the dis- 
turbances which the crag appears to have suffered, since its 
original deposition. 
In the interior, at e, there is a thick covering of sand and 
gravel upon the chalk, having the characters of an alluvium, 
partly, perhaps, marine, and partly terrestrial, and which seems 
to pass gradually in this district into the regular marine strata 
of the crag. 
Forms of stratification. — In almost every formation the in- 
dividual strata are rarely persistent for a great distance, the 
superior and inferior planes being seldom precisely parallel to 
each other ; and if the materials are very coarse, the beds often 
thin out if we trace them for a few hundred yards. There are 
also many cases where all the layers are oblique to the general 
* This section is compiled principally from one by Mr. Murchison, the others in 
this chapter are from drawings by the Author. 
