308 JURASSIC. 



winning the real north-country coal ! The shales vary from eight 

 to fifteen feet in thickness, and seem to form a connecting link 

 between the true Cornbrash and the Oxford Clay.^ (See Fig. 47.) 

 The Cornbrash is exposed at Gristhorpe and Scarborough, 

 where it is from two to fifteen feet in thickness. It is seen on the 

 North Shore and Castle Hill, and Red Cliff (Cayton Bay). It is 

 a very shelly rock, and has yielded a large suite of species, for our 

 knowledge of many of which we are indebted to ]Mr. J. Leckenby. 

 The Cornbrash has not been identified in the Howardian Hills. 



The Cornbrash is used for road-mending, and for building walls, etc. ; it is also 

 burnt for lime. As the name implies, the rubbly or 'brasliy' soil (especially in 

 the South-West of England) is well suited to the growth of corn ; according to 

 Prof. Buckman it contains more phosphate of lime than the subordinate 

 Oolitic formations. Analysis shows about 90 per cent, of carbonate of lime. 

 In Northamptonshire it makes a red soil, and is not reckoned so fertile. 



In the South of England its outcrop is marked by a line of villages which are 

 due, as Prof. Buckman remarks, not only to the fertility of the Cornbrash, but to 

 the circumstance that this porous rock, resting on the impervious Forest Marble, is 

 a collecting ground for water, which is kept up by the latter formation. - 



In the deep boring at Richmond, clayey and sandy beds, and 

 oolitic limestones 87 feet in thickness, were proved to belong 

 to the Great Oolite Series ; similar beds having a thickness of 

 64 feet occurred in the boring for Meux's Brewery, in London.* 



MIDLAND COUNTIES. 



Inferior Oolite Series. 



This series is divided as follows : — 



Zones. 



Lincolnshire Limestone ) . v c .... ;;.„• 



^ 11 , c, ^ > Ammonites Sozoerbyi. 



Collyweston Slate j 



Northampton ) Lower Estuarine Series. ) ,, ISIuychisoncB, 



Sands. ] Ferruginous Beds j ,, opalimis. 



Northampton Sands. 



This Series, which derives its name from the town of Northamp- 

 ton, comprises beds of ferruginous sand and sand-rock, which in 

 that neighbourhood include the zones of Ammonites Murchiso7i(E 

 and A. opalimis, thus representing the base of the Inferior Oolite 



1 P. Geol. Assoc, iii. 321, iv. 360. See also W. C. Williamson, T. G. S. 

 (2), vi. 145 ; and C. F. Strangways, Explan. Sheet 95 S.W. and S.E. (Geol. 

 Survey), p. 11. 



^ Journ. Bath and W. Eng. Soc. xiv., Q. J. xiv. 98. 



■' J. W. Judd, Q. J. xl. 748. 



