402 Frof. Bonney Sf Rev. E. Hill— Chalk Blufs. 



we examine that still in existence, or the districts which it formerly 

 covered, we find it has never done more to a limestone than mould 

 its surface into mound-like masses, and has often preferred to let 

 a gravel severely alone. In the Cromer district, as at Moen, Eiigen, 

 and the Isle of Wight, the chalk has undergone considerable flexure, 

 but that this was done in Glacial times is nothing but an hypothesis, 

 contrary to, rather than supported by, such evidence as can be 

 obtained. We have more than once examined the chalk platform 

 between Beeston Hill and Sheringham, and consider those little 

 insulated outcrops of that rock, rising a yard or two above the 

 beach, to be far more probably the indirect result of pre- Glacial, 

 perhaps long pre-Glacial, disturbances, which were afterwards ex- 

 posed to marine denudation probably in late Pliocene times. Even 

 the case figured in the Survey Memoir (at the bottom of p. 115) 

 is not in the least convincing. The Pliocene beds might have been 

 deposited round an old bank of chalk, just as is shown in the 

 section, and the fact that the higher of the flattened arches of flint 

 comes to an end at the upper surface is more consistent with flexure 

 followed by denudation than with the bending of a rock-mass, which 

 had a practically level top and horizontal flint bands. Still less can 

 it be proved that an ice-sheet has ever produced by its thrust an 

 ' inverted anticlinal,' even in a rock no harder than chalk, or is 

 competent entirely to shear off the top of that anticlinal. Allegations 

 of such things can, no doubt, be produced by the dozen, but in all 

 of which we know anything hypothesis takes the place of proof. 

 Mr. Keid himself cites one (p. 115) : " By Continental geologists the 

 theory (we should call it hypothesis) has been ali'eady applied to 

 the explanation of the even greater disturbances in the island of 

 Moen in Denmark." So it has been at Riigen, which also we have 

 carefully studied,' with the result that we found it difficult to treat 

 the explanation seriously. Did we admit its validity we should 

 be fully prepared to attribute the disturbances of the chalk at the 

 Needles or Culver Cliffs to the thrust of an ice-sheet ! 



Perhaps, however, the huge and strangely-shaped boulder now 

 visible in the cliffs between East and West Runton Gaps will be 

 cited as a proof of the bending powers of an ice-sheet. Here a mass 

 of chalk, which must once have been slab-like, after lying almost 

 horizontally for some fifty yards at the bottom of the glacial 

 deposits, bends rather suddenly ^ and runs rapidly up the cliff" to 

 within a short distance of the top. It is capped, as is not unusual 

 with the Cromer erratics, by a band of coarse flint gravel, which can 

 be seen, at any rate for a considerable distance, to be bent up with 

 the chalk. This mass, we may be told, has been sheared off, thrust 

 against some obstacle, and finally bent up by the advancing ice- 

 sheet. If so, the direction of the axis of the curve shows that 



' Quart. Journ. Geol. Soc, vol. Iv (1899), p. 305, and vol. Ivii (1901), p. 1. 



- It takes the shape of a fairly open hook, the two arms forming rather less than 

 a right angle ; the ' horizontal ' part of it slopes slightly westward ; a thin 

 extension of a rather sandy boulder-clay dies out beneath it, and then the chalk 

 probably touches (this part was masked by some talus) the Leda myalis sand. 



