GEOLOGY. 25 



6. Red and white marls. 



5. Thin bedded compact limestone, scarcely magnesian. 



4. Red and white marls and gypsum. 



3. Magnesian limestone in thick beds, in colour generally 



whitish or yellowish. 



2. Marl slate in thin layers. 



I. Yellow or purple sands, sandstones and marls. 



The contrast between the eastern and western development 

 is, however, very great. The following section for Yorkshire is 

 given on p. 210 in Woodward's Geology, ed. 1887 : — 



Feet 



Upper Permian f 6. Upper red marl and sandstone 50 



or Magnesian J 5. Upper magnesian limestone 120 



Limestone | 4. Middle red marl, sandstone and limestone 200 

 Series (Zechstein). 1^2 & 3. Lower magnesian limestone 120 



Lower Permian fi. White or yellow false-bedded sand (quick- 

 (? Roth-liegende). \ sand) with occasional breccia 20 or less 



The lowest bed of Sedgwick's series, so far as it represents 

 the Pontefract sandstone of Smith, has now been proved to 

 belong to the upper beds of the Carboniferous Millstone Grits 

 (J. C. Ward, Q. J. G. S., xxv. 294). Between the Wharfe 

 and the Nidd this forms an advanced escarpment ranging con- 

 siderably to the west of the real Magnesian Limestone. Here 

 it is a coarse-grained, irregularly bedded sandstone rendered 

 purple by infiltration from the Permian and Triassic rocks 

 above. It sometimes nearly approaches the appearance of a 

 conglomerate, and decomposes into irregular masses, as may 

 be well seen at Plumpton Rocks near Knaresborough. But 

 in North Yorkshire this bed is nowhere to be seen distinctly, 

 though numerous loose blocks which apparently belong to it 

 occur in the glacial detritus. 



The second and the fourth beds also are not anywhere 

 distinctly known in North Yorkshire. The latter, however, may 

 be seen near Tadcaster. The third bed or true Magnesian 

 Limestone forms a cliff 70 feet in thickness at Knaresborough 

 and cliffs from 30 to 50 feet thick on the banks of the Wharfe 

 and Tees. The upper part of these is a firm cellular con- 

 cretionary Magnesian Limestone and the lower part is more soft 

 and earthy in texture. 



Feb. 1888. 



