GEOLOGY. 29 



Stokesley, east of Northallerton, and at the entrance to the 

 Derwent valley between Barton Hill and Kirkham Abbey 

 stations on the York and Scarborough Railway.* 



THE JURASSIC SYSTEM. 



(13) The Lias Series. — For the typical section and for the 

 greatest thickness of the Lias formation we must go to Cleve- 

 land, where it forms the lower part of all the moorland escarp- 

 ments, and of most of the coast cliffs. Here we have it with 

 strata as under, beginning from above. 



3rd. The Upper Lias Clay or Shale, about 280 feet in 

 thickness, the upper part a soft shale from which alum was till 

 recently manufactured, characterised by Anwwnites communis ; 

 the lower part firmer and harder, with A. serpentinus. In this 

 are bands of ferruginous and argillo-calcareous nodules, and 

 a band containing jet. 



2nd. The Lronstone and Marlstone beds, about 470 feet in 

 thickness, consisting of highly arenaceous shales and laminated 

 calcareous sandstones, succeeded above by several bands of 

 nodular and stratified ironstone, which are worked extensively. 



I St. The Lower Lias beds, 378 feet in thickness, em- 

 bracing the four zones of Am. capricornus, jamesoni, oxynotus 

 and bucklandi, a nearly uniform mass of tolerably firm shale, 

 with many layers of nodular ironstone, and, in some inland 

 localities, laminated limestones at the bottom. 



The greater part of the series may be best examined in the 

 coast cliffs. It first makes its appearance from under the sands 

 beneath the Dogger at Blea Wyke,t nine miles north of Scar- 

 borough. From this point it rises gradually to the steep cliffs 

 at Peak on the south side of Robin Hood's Bay, where it 

 reaches 270 feet above high water mark. Here it is thrown up 



* See Woodward's Geology of England and Wales, ed. 1887, p. 247. 



+ Wyke or wick, when used as a termination or separate word in York- 

 shire topography, always means a small bay. This ' wick ' is quite dis- 

 tinct from the commoner ending, which is synonymous with the Latin 

 vicus, as in Norwich, Berwick. 



Feb. 1 888. 



