26 PHYSIOGRAPHY OF THE EAST RIDING. 



York, or that part of the latter, which for convenience we 

 shall name " Derwentland," from the important tributary of 

 the Ouse which intersects it. Geologically this area is 

 underlaid by rocks of Cretaceous (lower Cretaceous or 

 Neocomian, Speeton clay being the local name), Jurassic, and 

 Triassic age ; but there is no very considerable outcrop of 

 these rocks, owing to their superficial envelope of boulder 

 clay (over the Neocomian), and of a great extent and depth 

 of gravelly and sandy alluvium over the other formations. 

 There are gravelly accumulations, morainic in character, in 

 the vicinity of Escrick, a few miles south of the city of York ; 

 but far the greater part of Derwentland is evidently an 

 aqueous deposit of silt, and is peculiarly sandy in character. 

 The average depth of this deposit, as derived from the 

 figures of borings given in the Geological Society's Memoir 

 (by Messrs. Dakyns and Fox-Strangways), is somewhere 

 about fifty feet, being usually greatest near to the rivers. 

 At Barmby-on-the-Marsh, south of Selby, it is 92 feet ; 

 near Staddlethorpe, 59 feet ; and at Duffield and Pocklington, 

 58 and 42J feet respectively. Big sandy commons are the 

 characteristic features of this division, and good examples 

 are those of Pocklington, Barmby Moor, AUerthorpe, Riccall, 

 Skipwith, Bubwith, Houghton Moor, and Market Weigh- 

 ton Great Sandfield, all of which are noted resorts of 

 botanists and other naturalists. In agricultural parlance 

 Derwentland is spoken of as "The Levels," a name which is 

 exceedingly appropriate, inasmuch as it very accurately 

 describes the division which is certainly the most evenly low 

 land in East Yorkshire. Agriculturally it is also the most 

 fertile, and hence highly cultivated over most of its area. 

 Gradually the commons and moors are being brought under 

 cultivation ; and there only remains in isolated tracts any- 

 thing like a wide field for native plants. On the commons 

 above named are the only true peat-bogs in the Riding, and 

 these occur in patches where the sand is waterlogged. 

 These latter facts will not be without their significance to the 

 student most interested in our original and native flora. 



The drainage of Derwentland, as our name suggests, is 

 accomplished chiefly by the River Derwent, the largest east 

 bank tributary of the Ouse, together with the Hertford, a 

 feeder of the same ; but there are several smaller streams 

 besides. One, Speeton Beck, empties into Filey Bay. 

 Others, like the River Foulness (pronounced Foonay), now 

 in part coincident with the Market Weighton Canal, and 

 the North and South Cave Beck, debouch into the Humber 



