S. V. Wood, fun. — American and BritUh Surface- Geology. 15 



trace either of it or of any other kind of Glacial clay, and unless it 

 be concealed beneath the marshes of the Ancholme and those on the 

 north of the Humber, there does not appear to be any glacial clay 

 between those limits, though there is some sand and gravel ;' but 

 near York another great sheet of Glacial clay (destitute entirely of 

 chalk and sometimes destitute of boulders) begins, and, capped in its 

 lower elevations by the Hessle beds, extends uninterruptedly 

 northwards through the great vale which lies between the Pennine 

 Hills on the west and the Howardians and Eastern Moorlands on 

 the east, and is continued through Durham and Northumberland. 

 This sheet represents in my view the material produced by the 

 glacier-ice after this had shrunk back through the Vale of Pickering 

 and the Humber, and deserted the chalk country and the Lincoln- 

 shire troughs; and it is, I consider, of the same age as that which, 

 lying north of the Wolds and extending along the maritime border 

 of Durham and Northumberland, succeeded the purple clay of 

 Holderness. Looking at the distribution of the chalky clay thus 

 shown on the map, and at the character of the chalky clay which 

 forms the basement portion of the thick mass of which South-east 

 Holderness is made up, it is clear, I think, that the moraine en- 

 gendered north of Castor (except such as went northwards round the 

 angle of the Wolds and through the Pickering trough), travelled 

 out through the gorge of the Humber to form this basement clay of 

 Holderness, which teems with rolled chalk and is also largely 

 made up of the spoil of the clays which intervene between the 

 Trias and the Chalk; and that tlae moraine which makes up the 

 extensive clay deposit of the Eastern and East Midland counties has 

 been almost entirely generated south of the Humber and north of 

 the southern edge of the Fenland. 



By the motion of this land-ice down Lincolnshire from north- 

 west to south-east along the side of the Wold, the moraine 

 necessarily corresponds there in a great degree with the formations 

 on which it rests, and from which it was derived. From the motion 

 too of the ice being from the higher ground to the lower, simul- 

 taneously with and independently of the general southerly and south- 

 easterly motion of the whole mass, the debris degraded from the Wold 

 travelled off it into the trough on its south-western side to form part 

 of the great stream of intermixed mcrainic matter which, passing 

 down this trough, spread over the Eastern and East Midland counties. 

 By such motion of the ice, the moraine of pure Chalk which resulted 

 from the degradation of the Wold does in some places overlie and 

 oveidap that produced from the degradation of the Jurassic clays, 

 though by no means in that general way which Mr. Skertchlj^'s 

 diagram would imply ; and this motion will explain how Mr. 

 Skertchly's observations, being directed to the southern extremity of 



1 There is some thin clay over the Permian north of Doncaster, but whether this 

 is referable to the Glacial or to the Hessle clay I am unable to say. There is also 

 much sand, which is partly capped by clay, between Eetford and Doncaster, but these 

 are to the west of the line referred to in the text. Beds of sand and gravel also cap 

 the Liassic and Oolitic escarpments of the extreme N.W. of Lincolnshire. These 

 were called by Mr. Rome and myself " Denudation sands," but they may possibly 

 represent the purple clay. 



