internal Structure of the Magnesian Limestone. 55 



To this catalogue of sixteen outliers (only four of which are noticed in the 

 geological maps) might perhaps have been added the patches of limestone at 

 Little Crakehall in the hill north-east of Tunstall, above Catterick Bridge, and 

 near Eppleby ; also the three patches north of the Tyne. As, however, these 

 apparently unconnected masses cannot be regarded as outliers from any exist- 

 ing escarpment, I thought it better to mention them in the former section ; 

 considering them as remnants of the formation serving to indicate the general 

 direction of its range before it had been acted on by the great denudino- 

 currents, which have swept away some parts of it, and greatly modified the 

 external characters of those parts which remain. 



§ 5. Relations of the Magnesian Limestone to a succession of Coal formations. 



Having in the preceding details endeavoured to determine the superficial 

 extent of the formation, and also to describe some of its most striking external 

 characters, I now proceed to examine its relations to the several carboniferous 

 deposits with which it is associated. In the coal districts of Somersetshire and 

 Gloucestershire, the masses subordinate to the new red sandstone are obviously 

 unconformable to every portion of the older formations on which they are 

 deposited*. 



An examination of the denudation of the river Eden necessarily leads to the 

 same conclusion. The formation of new red sandstone extending from Kirkby 

 Stephen to Solway Firth, is composed of materials mechanically drifted into 

 a great depression of the strata, which was caused by the convulsion whicji 

 separated the chain of Cross Fell from the calcareous zone which skirts the 

 transition mountains of Cumberland. In some parts of this deposit are great 

 beds of conglomerate, which in their position, their relations, and minera- 

 logical character, are perfectly identical with the overlying conglomerates of 

 the Somersetshire coal-fields f. 



The geological relations of the magnesian limestone in its range from 

 Nottingham to the mouth of the Tyne are much more obscurely exhibited. 

 Through many large tracts of country (without the intervention of any con- 



* See Geol. Transac. New Series, vol. i. Plate XXXII. &c. &c. 



t Several masses of conglomerate, possessing the characters above described, are found in the 

 higher parts of the valley of the Eden near Kirkby Stephen, and on the hills south of Appleby. 

 Portions of many similar deposits are found within the limits of Whitehaven coal-field. At St. 

 Bees Head the coal-measures are surmounted by a series of deposits in the following order: — 

 1. A system of beds of coarse reddish siliceous sandstone. 2. Thin beds of magnesian conglo- 

 merate, surmounted by a system of hard and cellular beds of magnesian limestone. 3. Beds of 

 red marl and fibrous gypsum containing in their lower portion some thin bands of earthy carbo- 

 nate of zinc. 4. A great deposit of red freestone. 



