66 



THE GEOLOGIST. 



origin of these blocks can, according to their opinion, be 

 traced in an equally plausible manner from other causes, 

 requiring the assumption of less startling data, but which 

 would tend to produce a precisely similar effect, as regards 

 the distribution of the blocks, so far removed from their 

 parent bed. The existence of the gravel beds in the valleys 

 of North Wales, their curious relations, and their lines of 

 deposition, apart from the usual effects produced by ice, and 

 the universal occurrence of such traces in the vallies of Snow- 

 donia, offer important facts for the consideration of the 

 Geologist, as to the real circumstances under which glacial 

 masses were locally formed and the variety of causes which 

 facilitated their descent. We would therefore call particular 

 attention to these interesting statements, leaving our readers 

 to deduce their own conclusions, and to verify the theoretic 

 assumptions which we gave in the summary above referred 

 to. The paper submitted to the French Academy of Scien- 

 ces by M. Durocher, which we have reported in this month's 

 Geologist," adds another fact to the store of data on this 

 subject, which from its novelty will doubtless continue to oc- 

 cupy the attention of the geological world for some long 

 period yet to come. 



THE EDITOR. 



ORIGINAL COMMUNICATIONS. 



Note on the occurrence of a tooth of the extinct genus Lophio- 

 don, in the shelly conglomerate beneath the London clay, 

 Communicated by — Allport, Esq, author of the History of 

 CamberivelL 



A well sunk on Sydenham-common near the Croydon 

 Railway, passed chiefly through the blue clay. At the depth 



