371 



PROCEEDINGS 



OF 



THE GEOLOGICAL SOCIETY. 



POSTPONED PAPER. 



On the Superficial Accumulations and Surface-markings 

 o/ North Wales. By Prof. A. C. Ramsay, F.R.S., G.S. 



Read March 26, 1851. 

 [For the other Communications read at this Evening Meeting, see vol. vii. p. 200.] 



During several summers, while investigating the more solid geology 

 of North Wales in connexion with the Geological Survey of Great 

 Britain, my attention has been occasionally directed to the subject of 

 the action of ancient glaciers in that country, which were first de- 

 scribed by Br. Buckland in 1841 * ; and I have especially endeavoured 

 to discover traces of a sequence of events characterizing the glacial 

 epoch. 



On both sides of the Menai Straits, the low ground of Anglesea and 

 Caernarvonshire is often covered by a coating of " driftf ," composed 

 of beds of sand, gravel, and occasionally of clay, mingled with boulders, 

 and sometimes bearing marine shells characteristic of the period. 



On Moel Tryfan Mr. Trimmer discovered such shells in beds of 

 gravel, at the height of 1392 feet above the level of the sea J. From 

 Moel Tryfan, these superficial deposits are continuous, at similar ele- 

 vations, on the high grounds towards the valley of the Seiont, on the 

 seaward side of the mountain ranges of Caernarvonshire. The valley 

 of the Seiont is comparatively clear of " drift." Between Cwm Seiont 



* Proc. Geol. Soc. vol. iii. p. 579 et seq. See also Quart. Journ. Geol. Soc. vol. i. 

 p. 153 et seq., p. 300, and p. 460 et seq. 



t In this paper the term " drift " is used to denote the marine deposits of tlie 

 Pleistocene sea, without special reference to the transport of materials from a 

 distance. 



X Proc. Geol. Soc. vol. i. p. 331. 



