GEOLOGY. 27 



portion of that long line of valley which continues through 



the southern part of Yorkshire and which extends as far south 



as the neighbourhood of Nottingham and there expands into 



the great Triassic plain of the Midland Counties. 



In North Yorkshire these Triassic deposits are so thickly 



overlaid with glacial deposits that it is only in a very few places 



that they are exposed to view, and until recently we could only 



form a somewhat vague idea of their character and thickness. 



It is by some considered doubtful as to how far the two series 



of Bunter Sandstones and Keuper Marls are here distinctive. 



In the new salt -producing district of Cleveland the boring by 



Messrs. Bolckow and Vaughan, made in 1868, showed the 



following series : — 



feet. 



Surface deposits (chiefly glacial) 58 



Red marls and clays, two beds gypsum of 2ft. and 



6 ft. thickness 81 



White and red sandstone with gypsum veins 1 067 



Rock salt penetrated to a depth of lOO 



Limestone and conglomerate 7j 



Total depth reached 1313^ feet. * 

 A boring to 1,355 ^'^^t by Messrs. Bell Bros, in 1874 was 

 similar ; in this case the whole section has been preserved. 

 Details of these borings are given in the ' Hand-book of 

 Middlesbrough and District,' prepared for the British Associa- 

 tion meeting at York in 188 1. It will be seen that the York- 

 shire salt beds appear to occupy a much lower horizon than 

 those of Cheshire and Worcestershire. In Cheshire the series 

 is 1,700 feet thick, and in the Severn valley about 300 feet less. 

 The Bunter, or lower beds, consist principally of thick 

 sandstones, which are usually coarse in grain and, by the agency 

 of peroxide of iron, deeply tinged with red. In Nottingham- 

 shire this portion of the formation has an average breadth of 

 irom eight to ten miles, the soil which rests upon it being 

 chiefly composed of light yellowish sand, but all deep sections 

 of undisturbed beds are red. In Cheshire this part of the 



* The lower parts of this section are by some assigned to the Upper 

 Permian Marls. 



Feb. 1888. 



