338 HE. J. E. JIATIR ON LIMESTONE-KNOLLS IN [Aug. 1 899, 



the features which are observable on a larger scale — the thickening 

 of the limestone where pressure has been relieved, and its thinning 

 at points where pressure was greater ; the level ' stratification ' of 

 the centre of the knoll and its arching on the exterior ; the forma- 

 tion of breccias around the knoll, and the arching of the shale over it. 

 So much for the lessons taught by an examination of Draughton 

 Qiiarr}^ which I have described in deiail, on account of the interest 

 that attaches to the qnarr}' in consequence of its frequent descri])tion. 

 It is not to be supposed that the phenomena displayed here are local ; 

 they and others akin to them may be studied abundantly in the shales 

 with thin limestones south of the fault-system, and they illustrate 

 in a marked manner the changes which have taken place as the 

 result of earth-movement in the rocks south of the fault. 



IV. Desceiption or the Knolls neae Ceacoe and Settle, and 

 Notes on Knoll-steuctuee. 



A group of knolls, which I had the advantage of first seeing 

 under the guidance of Mr. Tiddeman, rises near Cracoe, west 

 of the Millstone Grit escarpment of Cracoe and Thorpe Fells. 

 The knolls run on lines roughly parallel to the escarpment, but 

 they also have a somewhat irregular arrangement into groups ; one 

 such group occurs immediately west of the escarpment, each knoll 

 forming a hill. Although each knoll forms an eminence, it does 

 not follow that the limestone of each is absolutely severed from that 

 of the surrounding knolls, and indeed only one (Stebden knoll) is 

 represented on the Geological Survey map as isolated from the 

 limestone by shale-bands ; but the structure of the ground makes it 

 highly probable that the overlying Bowland Shales abutted against 

 the upper portions of each knoll. 



The general characters of the knolls have already been noticed in 

 the extracts which I have given from Mr. Tiddeman's writings, a 

 prominent feature being the horizontality of the interior, the general 

 parallelism of the bedding of the exterior to the contour of the 

 knoll, and the obscurity of the bedding. The Cracoe knolls are 

 largely grass-covered, and nothing like a complete section through 

 a knoll is obtainable. The variations in the direction of bedding, 

 however, recall the structure described by Prof. Bonney as pseudo- 

 sfcjomatism, often upon a large scale, and signs of folding accom- 

 panied by fracture are not wanting, though it would be difficult in 

 the case of these knolls to convince anyone that this structure was 

 really due to extensive earth-movements. The same is true in the 

 case of the Settle knolls, and those at Downham, near Clitheroe, 

 which I have also examined, and therefore 1 propose to supplement 

 my description of these groups of knolls by some general notes upon 

 knoll- structure. 



Mr. Tiddeman describes the knolls as formed of ' white to grey 

 crystalline limestones of irregular form, and less visible bedding 

 [than that of the black limestones] except in the mass and on the 

 sides of the hills of which they consist.' They ' are crammed with 



