144 
HUGHES : INGLEBOROUGH. 
The pre-Carboniferous sea-plain was of course never a level 
surface, but the harder rocks stood out like the enamel in the 
tooth of an elephant while the softer dentine was worn away. 
We cannot, however, assume that the ridges of Silurian and 
Bala rocks which we observe to-day exactly measure the original 
inequalities of the sea bottom, but they must approximately 
represent the relative heights. In Chapel-le-dale they rise to a 
little short of 900 feet, and only fall to between 700 and 800 
feet. In Crummack Dale, where the tough Silurian sandstones 
cross the valley, they rise to only a few feet short of 1,200 feet, 
but where the Bala shales come out from below the Silurian 
south of Norber, the ancient surface on which the Carboniferous 
rocks were deposited falls to 700 feet above sea level (see 
Fig. 4). 
Similarly in Ribblesdale the tough sandstones are seen to 
throw the base of the Carboniferous rocks up, while the softer 
beds form troughs into which the earliest Carboniferous sediment 
was swept. Thus the grits and sandstones of Great Stainforth 
rise to near 1,250 feet above sea level. 
From these observations we should infer that the transverse 
valleys, such as that on the north side of and parallel to Thwaite 
Lane between Clapham and Austwick, or that along which the 
road from Austwick to Stainforth runs on the south side of 
Moughton Scar, really represent pre-Carboniferous E.S.E. and 
W.N.W. valleys in the softer beds of the Silurian and Bala. 
The great height of the base of the Carboniferous in Moughton 
Scar, above the general level of the Silurian and Bala beds of 
the low ground between Wharfe and Swarth Moor (see Fig. 5) 
is not, therefore, a proof of great denudation along that trans- 
verse valley since those beds were exposed, but the existing 
surface probably represents very nearly the original pre-Carbon- 
iferous sea bottom. 
The difference of level corresponds almost exactly with that 
seen in section along the west side of Crummack Dale, where the 
base of the Carboniferous rocks falls from nearly 1,200 feet south- 
west of Crummack to 700 feet south of Norber (see Figs. 4 and 5). 
