46 DESCRIPTION QF THE STRATA. 



of these discussions. — Let us now proceed to describe the regulai- 

 strata of the district, beginning with 



THE CHALK. 



In this district, as in the south-east parts of England, the chalk 

 is the uppermost rock, in respect of geological position. It holds a 

 prominent place among our strata; and, a» may be seen in the Map 

 and Section, it is of very considerable extent, forming nearly the 

 whole of those hills, or elevated grounds, denominated the Yorkshire 

 Wolds. These chalk hills lie in the form of an arch, or bow, having 

 one end at Flamborough Head, and the other near Ferriby on the 

 Humber, while the middle part bends inwards, toward the river Der- 

 went, making a sweep similar to the bend of that river, and in some 

 places parallel to it. The middle part is by far the broadest, the 

 distance from Driffield, where the chalk begins to sink under the 

 alluvium, to Scagglethorpe beside Malton, being about fifteen miles ; 

 while at the two extremities of the bow, both that which touches the 

 ocean, and that which reaches the Humber, the breadth is compara- 

 tively small. The Wolds, however, do not form one continued 

 mountain, but are intersected or indented by several valleys, some of 

 which are of considerable depth and extent. The curvature of the 

 arch described by these hills is greatest towards its northern termina- 

 tion, where the chalk, commencing at Flamborough, takes a north- 

 westerly direction by Hunmanby and Folkton (at which its most 

 northerly point occurs) ; and thence proceeds west or west-south-west 

 to Scagglethorpe. In this part of its course it is attended by the 

 Derwent, which meeting the Wolds near Ganton, is forced to make 

 a sharp turn to the west, flowing round the foot of the Wolds by Mal- 

 ton. From Scagglethorpe, the boundary of the chalk hills runs nearly 

 south, or south-south-west, by Birdsall and Wilton; after which, 



