276 ME. T. CODKINGTON ON SUBMEEGED EOCK- VALLEYS [Aug. 1 898, 



church, about 6 miles distant, the lowest Boulder Clay hitherto found 

 in the Thames Yalley.^ 



The Boulder Clay appears to occupy a similar position in relation 

 to the valleys of the Blackwater and the Colne, and also to the river- 

 valleys of East Anglia. Farther north, in the valley of the Humber, 

 the relation of the Glacial beds to those of more recent age is the 

 same as in the western valleys which have been described. The 

 chalk-bottom at Hull " is as much as 87 feet below the level of low 

 water, and on it he 50 or 60 feet of Glacial beds — Purple Clay, Hessle 

 Sand, and Hessle Clay — upon which is a peat-bed with trees rooted 

 in the Hessle Clay, as much as 17 feet below the level of low 

 water. Above the peat is silt with Scrobicularia^ in some places 

 30 feet thick. Still farther north, the Esk at Whitby, the Tees, and 

 the Tyne flow in pre-Glacial valleys, of which the rock-bottoms are 

 many feet below the level of low water, and which contain Glacial 

 beds, peat, and silt in the same succession. 



The resemblance between these northern valleys and those to 

 which this paper relates, and the difference between both these 

 groups and the valleys nearer to the former land-connexion with 

 the Continent, are not, perhaps, without significance. It is, however, 

 a matter beyond the scope of this paper, in which my object has 

 been to show that over a large extent of coast in South Wales, 

 South Devon, and Cornwall there are valleys excavated in rocks of 

 different kinds, the bottoms of which are now as much as 80 and 

 110 feet below the level of low water, which are partly filled with 

 dej)osits not older than the submerged forests, beneath which de- 

 posits of Boulder Clay and other Glacial beds are found overlying 

 the rock-bottom ; and that consequently these valleys must have 

 been excavated to their present depth before the Glacial Period, 

 and before the rivers in the eastern part of the English Channel, 

 tributaries to the old Solent and the river Thames, had cut through 

 the Glacial deposits which border on their valleys at high levels. 



Discussion. 



Mr. Steahan wished to add his expression of welcome to the 

 Author after a long absence. The description given of valleys filled 

 with mud to so great a depth below sea-level emphasized the fact 

 that the land must have stood at a considerably higher level in com- 

 paratively recent times, not only in South Wales, but all round our 

 coasts. In most cases the tide had repeatedly scoured out and 

 redeposited the muds and silts ; but in the almost land-locked area 

 of Barry Dock, which he (the speaker) had recently described, the 

 sequence of deposits had been preserved, and more than one land- 

 surface remained intact, the lowest, with land-shells and tree-stools- 

 in place, proving a subsidence of about 60 feet. There, moreover,, 

 proof had been obtained that the change of level had taken place 



1 See T. Y. Holmes, Quart. Journ. Geol. Soc. vol. xlviii (1892) p. 365. 

 =» J. C. Hawkshaw, Proc. Inst. C.E. vol. xli (1875) p. 93 ; Wood & Eotne,. 

 Quart, Journ. Geol. Soc. vol. xxiv (1868) p. 182. 



