
nastiest 
ee ea — ae = 
— < ~ ene oe ee —— _~ 
. 
composed principally of limestones, which, as they dip gently 
eastwards, are succeeded by a series of argillaceous beds, 
forming again a region of undulating plains. Continuing 
our traverse in the direction of the dip, we eventually 
encounter another broad belt of high ground—the escarp- 
ment of the Chalk. This escarpment is succeeded @immmre 
turn by a low-lying region composed mostly of soft clay 
strata, and other more or less non-indurated materials. 
When the strata, instead of being inclined in one direction 
for long distances, are arranged in a series of gentle folds, 
escarpments continue to present themselves wherever relatively 
hard beds crop out at the surface. In this way we not 
infrequently find lines of escarpment facing each other, as 
in the well-known case of the North and South Downs which 
overlook the intervening Weald. Here we have an example 
410 STRUCTURAL AND FIELD GEOLOGY 

FIG. 144.— SECTION ACROSS THE WEALDEN AREA—A DENUDED ANTICLINE. 
of a highly eroded anticlinal fold, which is always a weak 
structure, and readily reduced by epigene action. (Fig. 144.) 
Synclinally arranged strata do not succumb so easily—the 
structure is relatively strong, and makes a stouter resistance. 
The rocks so arranged are not degraded so rapidly as the 
same rocks would be if disposed in the form of an anticline. 
In short, it is with gently undulating strata as with the 
steeper and more abrupt convolutions of Tectonic mountains 
—anticlines are frequently replaced by hollows, while synclines 
tend to be developed into heights. 
In fine, one may say that however simple or complex the 
geological structure of a highly denuded region may be, the 
configuration of the ground, as worked out by epigene action, 
has been determined mainly by the character of the rocks 
and the manner of their arrangement. In a word, when we 
have deciphered the geological structure of a country, we 
have at the same time discovered the origin of its hills and 
mountains, , 

