490 THE CHALK AND DKIFT IN MOEN. [Aug. I906, 



whether he attributed the horizontal beds to introduction by water- 

 action from above. It seemed rather difficult to understand how 

 Boulder-Clay, more or less stratified, underlying the Chalk could 

 be brought in from above. If it was washed in from above, the 

 selective action of water might come into play, as suggested by the 

 last speaker, and one of the slides shown certainly suggested this. 



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 not know how many, years ago that I visited the island of Moen, 

 in company with the late Prof. 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 may be 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 palaeolithic 

 implements. If I remember rightly, a similar pipe in the Valley of the 

 Somme, cited by Prestwich, is 90 feet deep.' 



He replied to Mr. Horace Woodward that his faith in the Baltic 

 Glacier did not rise to a belief that it could dislocate the Chalk 

 before its own existence. The fissures were made and enlarged 

 before the Drift came which fills them. He thanked Mr. Lamplugh 

 for instances oi» pre-Glacial fissures on the Yorkshire coast. He 

 had not actually touched the Drift-inclusions half way down 

 cliffs 400 feet high ; but some were at shore-level. In reply to 

 Mr. W'hitaker, he did not feel sure that re-made Drift was always 

 easily distinguishable, but his own view was that the hollows had 

 iu general been filled during the deposition of the Drift. 



