133 
PHYSICAL GEOGRAPHY OF THE DISTRICT. 
An observer stationed on the swelling margin of the eastern wolds, 
at an extreme height of eight hundred and five feet, or on the steep 
escarpment of the oolitic moors, which rise to one thousand four 
hundred and eighty-five feet, may look to the westward over a 
uniformly low plain or vale, which from the Tees ranges southward 
across the Ouse, Wharfe, and Dun, and is, with some variation of 
character, prolonged parallel to the Trent as far as Nottingham — 
Through all this extensive course, it is flanked on the east by lias 
clays and limestones, which are themselves overlooked by parallel 
walls of oolite and chalk, and on the west by a regular terrace of 
magnesian limestone. From one end to the other it is underlaid by 
red and coloured clays and sandstones, which, by some ancient devas- 
tations of water, have been deeply and irregularly excavated into 
subterranean valleys, and again overspread by vast heaps of trans- 
ported materials. In particular places these materials lie in undu- 
lated ranges of hills, indicative of the direction of powerful currents, 
but in that portion of the great plain which belongs to Yorkshire 
the wide uniformity of the surface is seldom broken, except by in- 
sulated hillocks which rise barely to the height of one or two hun- 
dred feet above the sea, 
The terrace of magnesian limestone above-mentioned rises, in almost 
all situations in Yorkshire, by an imperceptible gradation out of this 
great plain of new red sandstone, to a height of two hundred, three 
hundred, and four hundred and fifty feet, and ends towards the west 
in a well marked often very abrupt escarpment of one hundred or 
more feet descent. The strata lying beneath the limestone terrace 
on the west are unconformed to it both in dip and direction , con- 
sequently, in different situations, different strata come in contact with 
the lower plane of the limestone series. F rom the southern border 
Yorkshire nearly to the river Wharfe, the magnesian limestone 
rests on coal measures ; thence northward to the Tees on the sub- 
jacent strata of millstone grit and shales of the mountain limestone 
series; the general aspect of the western country varies accordingly. 
