HUGHES : INGLEBOROUGH. 
U9 
The fault which crosses the top of Ingleborough has a very 
small displacement. Indeed, it may be only a shake and crack 
over a pre-Carboniferous fault below. But it is well worth careful 
examination, as it has obviously affected denudation, and yet runs 
over the highest ground in the district. Crossing the south end 
of the Millstone Grit, it cracks the Main Limestone and the 
Yoredale Grit, and can be traced as a long peat-covered hollow 
across the Mountain Limestone below. 
A point which is specially deserving of careful attention is 
forced upon our notice by an examination of the great cliff, which 
represents one wall of the fault in the Twis valley. If two curved 
Fig. 8. 
rock faces of that kind are relatively shifted, it is clear that the 
protuberant parts must often hold the walls of the fault apart 
and spaces be left which, if not filled with, crushed material, will 
offer suitable conditions for the precipitation and crystallisation 
of mineral matter (see Fig. 7). As a matter of fact, we do find 
veins and lodes commonly occurring in lenticular cavities which 
appear to be formed in just that way. Sometimes when the fissure 
cuts across strata of various degrees of compressibility the more 
yielding beds are squeezed out, filling the crack completely and 
