254 PROCEEDINGS OF THE GEOLOGICAL sociETr. [Jan. 22, 



tlie J^orfolk coast. But in regard to the lowest Hessle gravels, 

 which rest upon chalk and are covered by Boulder-clay, I had 

 always a different opinion ; and when, in 1853*, I published a 

 classification of Yorkshire deposits, in which the terms Preglacial, 

 Glacial, and Postglacial were employed, these gravels, as well as the 

 contents of Xirkdale Cave, were counted by me as oi Preglacial date, 

 while the Bridlington Crag was regarded as only a little later than 

 the Upper Crag of Norfolk. 



Now all this is changed ; the cavern-mammalia are regarded as 

 Postglacial, the Hessle clay becomes an upper Boulder-clay, and the 

 Bridlington Crag is treated as a part of the same great series of 

 drift deposits, after suffering divorce from its partner in Norfolk. 



While these questions are still sub judice, fresh evidence may 

 be admissible. I have something to offer on each of them, but at 

 present limit my remarks to the Hessle section of Boulder- clay, 

 gravelly diifts, and chalk. 



The Hessle clay, if it be the upper part of the great Holderness 

 deposit, and not met with beyond the outcrop of the chalk, must 

 be designated as a third Boulder-clay ; for everywhere north of the 

 promontory of Flamborough — at Speeton, Filey, Scarborough, and 

 Whitby — the Boulder-clay is in two layers, separated by gravels and 

 sands, or sands only, water not unfrequently coming out of the in- 

 termediate layer. It is quite possible that this series of clays may 

 really be triple ; it is certainly double at several points, both north 

 and south of Flamborough Head. 



The clays, fuU of fragments of various rocks, which appear north 

 of Flamborough Head, were certainly deposited on a previously 

 waterworn surface. The level vale of Pickering, partly formed 

 upon a surface of Boulder-clay, may be regarded as a large Preglacial 

 vale, or sea-loch, which became blocked during the Glacial depres- 

 sion by drift at its eastern end. Through this drift short streams 

 have since cut their way to the sea, to which, in earlier times, the 

 Derwent had probably flowed by a short and rapid course, accom- 

 panied, most likely, by the Seven, Eye, and other western waters, 

 which now descend to the Humber through the gorge at Malton. 



In like manner Scalby Beck, north of Scarborough, runs in a 

 channel which it has cut through drift, which drift lies in an older and 

 broader valley, cut into the sandstones and shales in Preglacial times. 

 Just such phenomena appear in the broken cliffs and road- cuttings 

 between Whitby and Sandsend : a broad old hollow of Upper Lias 

 has been heaped full of northern drift, through which, at a later 

 time, the small streams have won their uneven way to the sea. 



On the surface of the subjacent rocks, under the drift, there is to 

 be seen, at a few places, a peculiar rubble, composed mostly of por- 

 tions of these rocks, much like what is occasionally seen at the 

 surface of strata which have been exposed to disintegration by at- 

 mospheric agency, and, like that, occasionally displaced (Filey Brig). 



By observations of the same kind at Dane's Dyke and other chalk 

 valleys filled with drift south of Flamborough Head, the same pro- 

 * Rivers, Mountains, and Sea-Coast of Yorkshire, 1853. 



