300 Sir R. R. Roworth— Dislocation of the Chalk. 



mass, with flint-bands nearly vertical, and now half-quarried away, 

 must have measured some eight yards in length; according to the 

 workmen's account, the part left is ten feet wide by eight feet in 

 height. Another mass, eight feet broad, was just being exposed 

 at the time of my visit, June 1883 ; while near the entrance there 

 was a third, long tabular mass of chalk about 20 feet long, and 

 passing into reassorted white marl ; but the greater part having 

 its bedding so little disturbed that it might have been in situ." 

 Speaking of this latter, he continues : — "The seam of dark-grey marly 

 clay at the base of the chalk was from two to six inches thick, and 

 exactly like the bands which so frequently occur in the chalk-with- 

 flints. It would seem, therefore, that a mass of chalk, together 

 with the clay-band, had been quarried out of the hill and embedded 

 in the gravel without disturbance of its bedding or destruction 

 of the clay." ("Geol. North Lincolnshire and South Yorkshire," 

 p. 171.) It seems to me that facts like these are only consistent 

 with the cause I urged in my previous paper. 



The great earth-movements that raised the chalk wolds of 

 Yorkshire, in doing so necessarily caused transverse fissures at right 

 angles to the anticlinal lines, thus forming the steep-sided transverse 

 dales which mark them. This was well seen and urged by the 

 older geologists, who had studied mechanics and physics, and did 

 not construct their camels out of their imaginations only. The most 

 important of all these transverse valleys is probably that in which 

 the Humber flows, and which, if not a fissure, presents to us the 

 chalk bent down or sunk to a great depth below high-water mark, 

 and the hollow filled up by the chalky clay, etc., showing that it 

 was made at the same time as the great depressions of the chalk 

 marked by the well-borings at Boston, in Lincolnshire, and Yarmouth, 

 in Norfolk. 



The steep sides of these buried valleys are remarkable. Thus, 

 Mr. Jukes-Browne says of a gravel-pit west of Wold Newton church : 

 " From this depth of 40 feet the chalk rises steeply on either side in 

 a series of rough slopes" (op. cit., p. 171). Again, Mr. C. Eeid 

 says : " Great Limber is partly on gravel and partly on chalk, 

 the gravel having its limit generally well defined by a sharp rise 



of chalk The abrupt rise of the chalk at Limber brickyard 



is very curious ; for one of the cottages belonging to the pit is 

 on chalk, while not 80 yards away, on the same level, there is 

 at least 37 feet of sand and warp " (id., p. 180). 



Turning to the valley of the Humber, Mr. C. Beid, in his " Geology 

 of Holderness," tells us that under it " there is evidently a con- 

 siderable thickness of boulder-clay, though none of the borings yet 

 made have shown the full depth of the old, probably pre-Glacial, 



Humber valley They prove that boulder-clay, interstra- 



tified with sand and gravel, reaches a depth of at least 83 feet 

 below the present level of high- water \ and, judging from the dip, 

 there will be a still greater thickness in the old channel." He 

 quotes other cases thus : one boring, 300 } r ards east of Hessle 

 ierry, reached chalk at 42£ feet below high-water; a second, 



