CHALK. 47 



diverging from the Derwent, it takes a south-east course by Market 

 Weighton to Ferriby, where it meets the Humber. The whole cir- 

 cuit thus described amounts to about sixty miles, without reckoning 

 the sinuosities of the outline. The chalk stratum, after being inter- 

 rupted by the Humber, re-appears on the south side of that river; and 

 traversing Lincolnshire, continues its coui-se, with a few interi'uptions, 

 to the southern shoi-es of England. 



The highest parts of the Wolds are towards the outer edge of the 

 arch which they describe; the interior part gently sloping from every 

 side towards the plain of Holderness, while the exterior presents a 

 bold and lofty front, or at least a steep declivity. The chalk first 

 appears on the coast, above the level of the sea, about a mile north 

 from Bridlington Quay. From thence it gradually rises towards 

 Flamborough and Speeton, where it reaches the height of about 400 

 feet or upwards; there being precipitous cliffs at Speeton about 300 

 feet high, the top of which is many feet below the elevation of the 

 adjoining heights. In proceeding westward, we find the back part 

 of the Wolds assuming a much more lofty form. Wilton beacon is 

 ascertained to be 809 feet above the level of the sea. The hills again 

 diminish in height as they approach the Humber; yet at Hunsley bea- 

 con, only about six miles from Ferriby, the elevation is still 531 feet. 

 •At the same time, it must be observed, that the thickness of the chalk 

 is not every where equal to the height of the hills; for where the 

 Wolds are highest, we find some of the next strata, occupying the 

 lower part of them, beneath the chalk. The thickness of the latter, 

 however, cannot be less in some places than five or six hundred feet. 



The dip of the chalk strata, ashas already been intimated, is not 

 in one direction only; for the slope of the hills, from each part uf the 

 semicircle which they form, being towards the centre, that is, towards 

 the middle part of Holderness, it follows, that at Flamborough and 

 Bridlington the dip is to the south ; about Driffield and the middle 



