270 
HUGHES : INGLEBOROUGH. 
above O.D., sometimes a little more, sometimes a little less, 
according to the original foldings of the strata, the sinkings 
due to underground waters, and the irregularities of surface 
denudation. 
To follow up the section still further we may pass on to 
the bed of the stream which runs down from the sandstone 
at the top of Farrer's Allotment hy the Shooting Box to Sulber. 
The Mountain Limestone everywhere yields along the bedding 
planes, so as to give rise to the bare jointed surfaces locally 
known as " clints " or " helks." This is especially the case near 
the top of the Great Scar, where tlie overlying Yoredale shales 
are apt to be removed wholesale. 
The terraces thus formed catch on their fissured surface 
all the water that runs off the steep slopes of Carboniferous 
Shale or Boulder Clay above, and discharge it in springs and 
kelds, where it is arrested by impervious strata below. Thus 
we find on the top, swallow holes, at the base, caves. 
This happens also to some extent in the case of every sub- 
ordinate limestone in the Yoredale Series, which can frequently 
be traced — the upper boundary by the lines of swallow holes, 
and the lower boundary by the springs along the hillside where 
the limestone itself is buried under superficial deposits. We 
see on these extensive floors of bare limestone the pattern of 
the jointing, and how the presence of vegetation and water 
running off peat aids the chemical decomposition of the rock 
along the joints. (Plate XXXIV., Fig. 1, shows the margin of 
the clints west of Sulber, where denudation is most rapid owing 
to the action of the acidulated water from the adjoining peaty 
moor. The figure is standing on one of the long blocks of 
limestone between the master joints, which are weathered into 
various forms hke procumbent statues or the tracery of a 
Gothic window. He is pointing to the place where the Sulber 
fossils mentioned on p. 275 were procured. Behind him higher 
strata, but still belonging to the Great Scar, are seen creeping 
over the bed on which he stands, showing that these clints are 
not the highest beds of the Great Scar Limestone. Penegent 
is seen in the distance.) We know that the surface of the 
beds is similarly removed, often leaving pedestals of the 
