354 MK. J. E. MAKE ON LIMESTONE-KNOLLS IN [Aug. 1 899, 



the minor faults which would inevitably accompany repetition of 

 the strata are marked by breccias differing in character according 

 to the nature of the rocks in which they were formed. If my 

 views be true, we are dealing with a great group of yielding strata 

 sandwiched in between two more rigid rock-groups, and all affected 

 by the thrusting of other strata over them from the north. The 

 result would be that the lower rigid strata would be slightly affected, 

 the upper greatly so, but owing to their rigidity they would be 

 packed in great blocks, rather than twisted and torn into small 

 fragments ; while the central groups of yielding deposits, rolled 

 between these others, would be twisted and torn in every direction, 

 and would tend to accumulate in the places where downward 

 pressure was relieved, and to be squeezed from those where it was 

 greatest, just as I said was the case with the little ' model ' knolls in 

 the left arch of Draughton Quarry (p. 337). 



This hypothesis appears to me to account for all the phenomena 

 that I have seen in the area south of the Craven Fault, and to 

 furnish a connected explanation of them which is not at variance 

 with that given of similar districts elsewhere, or with our knowledge 

 of the effects of epeirogenic movements in general. 



A few words concerning the age of the movements which I believe 

 to have been responsible for the formation of the knolls may be 

 inserted here. The great anticline which is affected by the Craven 

 Faults is post-Carboniferous and pre-Permian (using the term ' pre- 

 Permian ' with reference to the Permian rocks which occur on the 

 east side of the Pennine Chain, for the Coal Measures are affected 

 by the fold, and the Permian rocks are not). The Craven Faults 

 are subsequent to this, and they affect the Permian rocks which 

 occur near Westhouse, lying upon the Coal Measures of the Ingleton 

 coalfield. How long a time elapsed after this Permian breccia 

 was deposited before the faulting took place we cannot say, but the 

 general character of the movement, and the resemblance of the 

 consequent phenomena to those exhibited as the result of the 

 Hercynian system of movements in the South of England, would 

 suggest that the main movements occurred in Permo-Triassic times, 

 though it is by no means certain that they were not continued until 

 a later period. 



YIII. Knolls op Limestone in other Areas. 



Examination of knoll-shaped masses of limestone in other areas 

 yields results similar to those which I have enumerated, and in all 

 cases, as already stated, the knoll-shaped masses occur in regions 

 which have undergone movements of an orogenic character. Among 

 the features which I take as characteristic of knoll-structure are : 

 (i) sudden expansion of the limestone in the knoll ; (ii) irregularity 

 of bedding, changes in dip and strike being constantly noticeable, 

 and determining the characteristic weathering which results in 

 the knoll-form, and not in continuous escarpments ; (iv) crystalline 



