Vol. 59.] IN THE CHALK NEAR E0YST0N. 373 



Mr. Whitakee said that, if his former colleague, the late 

 Mr. Penning, were alive, he would probably accept the views put 

 forward by the Author. Mr. Penning and he had chronicled the 

 facts as they saw them, and they could not at that time 

 attempt the division of the Chalk in the same detail as is possible 

 nowadays. Moreover, they were working on the old 1-inch map. 



Prof. Sollas agreed with the Author in attributing the dis- 

 turbances to pressure exerted by ice. It was probable that with 

 the progress of investigation similar disturbances would be found 

 in other localities, and they might even become recognized as an 

 evidence of glacial action in districts where other evidence, such as 

 Boulder- Clay, was absent. On the flanks of Shotover Hill, near 

 Oxford, a local inversion of the Corallian on the Kimmeridge Clay, 

 and of the latter on the Portland Sands, may be observed : the 

 inversion is associated with a thrust-plane which, where it affects 

 the Kimmeridge Clay, is beautifully slickensided. On Cumnor Hill, 

 situated about 6 miles to the west of Shotover, and on the other 

 side of the Thames Valley, Miss Healey has lately found a similar 

 inversion ; a long tongue of Kimmeridge Clay is here thrust over 

 the iron-sands, and the overlying Pleistocene gravels are involved 

 in the movement. Here again the thrust-planes are slickensided, 

 and the clay exhibits a kind of foliation similar to that which gives 

 the characteristic ; tea-leaf ' structure to some Boulder-Clays. 

 Mr. Montgomery Bell has found similar but less marked disturbances 

 in the Oxford Clay, also affecting the overlying Pleistocene gravels, 

 and producing ' tea-leaf ' structure in the clay. It was intended 

 to bring a detailed account of these and similar disturbances before 

 the Society on another occasion ; in the meantime, they were men- 

 tioned as offering a confirmation of the Author's explanation. 



The Rev. J. F. Blake drew attention to a description and figure 

 which he had given, in vol. v of the Proceedings of the Geologists' 

 Association, of some locally-upturned Chalk in Yorkshire ; this 

 he had no hesitation at that time (1877) in ascribing to the action 

 of ice. He enquired how the buried Boulder-Clay described by the 

 Author was supposed to have reached its present position. 



Mr. P. W. Haemee said that he was much interested in the paper 

 just read, especially as it seemed to confirm the views enunciated 

 by Searles V. Wood, Jr., many years ago, as to the origin of the 

 Chalky Boulder-Clay. It had been often held that the ice to which 

 the latter was due came from the North Sea over North-Eastern 

 Norfolk. That this was not so is shown by the fact that no 

 Chalky Boulder-Clay exists between Cromer and Norwich, though 

 it comes on suddenly to the south of that city. If, on the contrary, 

 it came from the north-west, as Wood believed, fanning out from the 

 Fenland region in all directions, it would be in the neighbourhood 

 of the latter, where the ice lay thickest, that disturbance of the 

 underlying Chalk, similar to the cases described by the Author, 

 would be met with. In Eastern Suffolk, where the ice was thinner, 

 it would have had less erosive power. In that district it overrode 

 the Middle Glacial Sands, and, as a rule, without disturbing them. 



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