internal Structure of the Magnesian Limestone. 109 



of red sand^ sandstone, and marl; and they are of such complex and irre'nilar 

 structure, that it is not, I believe, possible to separate them into any natural 

 divisions which, in their range through the whole island, preserve a constant 

 relation to each other. There is, however, in that part of the system which 

 rests immediately on the back of the magnesian limestone series above de- 

 scribed, an approximate order which requires a short notice. 



In Nottinghamshire the yellow limestone is surmounted (as has been already 

 stated) by a thick formation of sand and sandstone, which ranges nearly due 

 north through the forest lands of the county into the southern plains of York- 

 shire, occupying on the average a breadth of eight or ten miles ; but to the 

 north of Doncaster it disappears under the alluvial and diluvial plains which are 

 spread out between the banks of the Don, the Air, the Wharfe, and the Ouse. 

 The soil resting upon it, is chiefly composed of a light yellowish sand ; but all 

 the deep sections of the undisturbed beds, exhibit a reddish colour. This 

 sandstone is generally coarse, — often nearly incoherent; passes here and there 

 into a fine conglomerate ; contains many small rounded pieces of quartz, and 

 (judging from the appearance of the diluvium associated with it) appears also 

 to contain many rounded pebbles of ancient quartz rock. Immediately over 

 the preceding sandstone is a deposit of bright red-coloured gypseous marls, 

 which form the subsoil of the eastern clay lands of Nottinghamshire. The 

 escarpment of these beds is seen in a well-defined chain of low hills which 

 crosses the great North road above Markham Moor. They gradually sink 

 down into the great plain which is drained by the Trent ; and a few miles to 

 the east of that river they are surmounted by the lias. 



These two great divisions of the new red sandstone (which, when taken in 

 association with the deposits already described, may be called the upper red 

 sandstone, and the upper red marl and gi/psum), appear also to exist in the 

 county of Durham, as for as we can judge from the denudations on the banks 

 of the Tees, and from the coast section between Hartlepool and the mouth of 

 the same river. The magnesian limestone, notwithstanding the immense 

 accumulations of diluvium, is evidently surmounted by a zone of strata cliiefly 

 composed of red sandstone ; and the red sandstone is, in the direction of the 

 dip, succeeded by an extensive deposit of red gypseous marls, which are seen 

 in several open sections not far from the mouth of the Tees. 



Whether the same great divisions are prolonged through Yorkshire cannot 

 be determined ; as many parts of the county do not offer a single natural or 

 artificial section which throws light upon the general arrangement of the for- 

 mation. 



In Ripon Park there are extensive gypsum pits ; and gypseous red marls 



