238 Reports and Proceedings — Geological 8ociety of London. 



In 1899 Professor Bonuey and the writer published a paper oa 

 Moen and Riigeu : the present contribution contains results of 

 further studies. 



The problem of Moen is to account for portions of Drift, isolated, 

 • and seemingly included, in cliifs of Chalk. It has been generally 

 assumed that these portions occupy dislocations, and that the disloca- 

 tions were either simultaneous with, or subsequent to, the deposition 

 of the Drift. But, in this paper, cases are described where Drift is 

 seen to occupy cavities in dislocations, which had been water-worn, 

 and consequently had been produced, before the advent of the Drift. 

 The assumption hitherto generally made is, therefore, incorrect : 

 the Chalk had been disturbed in pre-Glacial times. A probable 

 assumption that there were pre-Glacial hills and clififs similar to 

 the present, with similar clefts and furi'ows in the cliffs, which 

 were covered in Glacial times with a mantle of Drift now in course 

 of removal by denudation, explains evei'y variety of Drift inclusion. 

 These varieties are described, and proofs are given of such an over- 

 lying mantle of Drift, even now over 100 feet thick on the flanks 

 of the hills, and rising to their summits. 



Differences from the Kiigen phenomena are noted and explained. 

 An apparent upward succession of Boulder-clay, shingle-beds, sand, 

 and scattered boulders is discussed. 



Slopes of uniform inclination which rise from the beach, often 

 60 feet and more, to the bases of the vertical cliffs, appear to be 

 talus-slopes. In reality they are everywhere solid Chalk, with only 

 a skin of debris : this suggests post-Glacial changes in sea-level. 



Certain weathered-out hollows in cliff-faces indicate a way in 

 which isolated portions of Drift might, when denudation had com- 

 menced, be long protected from destruction. 



One instance of a Chalk boulder included in Drift emphasizes the 

 general contrast, not likeness, between Moen and Cromer. The 

 position of the Drift in Moen is similar to that of the Boulder-clays 

 at Flamborough and along the Yorkshire coast. Had the Yorkshire 

 Chalk been dislocated as that at Swanage or Lulworth, probably we 

 should have in England similarities to Moen. 



The author, with the Chairman's approval, read the following 

 extract from a letter which he had received from Sir John Evans: — 



" It is, I do uot know how many, years ago that I visited the island of Moen, in 

 company with the late Professor Steenstrup. The impression left on my mind by the 

 abnormal contortions of the Drift was that they might, to a great extent, be due to 

 the corrosion and erosion of the Chalk below, by the infiltration of water charged 

 with carbonic acid. The surface of the Chalk in Hertfordshire is remarkably 

 irregular, with deep indentations and numerous pinnacles. "Within less than 100 

 yards of each other shafts may be sunk through Drift, and the Chalk in one shaft 

 maybe 30 or 40 feet below the surface, and in another only 10 or 15 feet. In a shaft 

 about 6 feet in diameter, that I have lately had sunk near Berkhamsted Common, the 

 surface of the Chalk on one side of the shaft is about 6 feet higher than it is on 

 the other. 



"On the Great Northern Railway, near Knebworth, there are pipes eroded to 

 a great depth in the Chalk, which must have been formed since Pleistocene times, 

 inasmuch as in the gravels let down in the pipes there are paliEolithic implements. 

 If I remember rightly, a similar pipe in the Valley of the Somme, cited by Prestwich, 

 is 90 feet deep." 



