554 Prof. Sedgwick on the Classification of the Strata [May^ 



marks their passage through the cliff. They are altogether not 

 more than fifteen or twenty feet thick, and in other places are, 

 perhaps, considerably less ; but they require some notice from 

 their peculiar mineralogical character, and from their continuity. 

 They are, however, chiefly interesting from the fact of their 

 forming a separation between the productive and unproductive 

 portion of the peculiar coal formation to which they are subordi- 

 nate. Traces of bituminous shale may (as has been stated 

 above) be found in certain parts of the formation above these 

 beds of limestone, but no where of sufficient purity and thick- 

 ness to be of any value. 



From Cloughton Wyke to the eastern end of Robin Hood's 

 Bay, the whole coast is composed of alternating beds of sand- 

 stone and shale ; the greater part of which are, in composition 

 and mode of arrangement, nearly identical with the beds of the 

 great coal formation which are exposed on the coasts of Cumber- 

 land and Northumberland. This fact is of importance, and 

 should teach us great caution in identifying distant deposits 

 without first studying every fact connected with their natural 

 history and relations. Almost all the higher parts of the coast, 

 from Robin Hood's Bay to Saltburn, where the cliff terminates 

 in the sandy plain of Redcar, are composed of the lower mem- 

 bers of the series resting on the alum-shale ; and the same remark 

 may be applied to the structure of the hills which overhang the 

 plain of Cleveland. The sandstone is extremely variable in its 

 colour and structure. It is often iron-shot, and sometimes con- 

 tains balls and irregular concretionary beds of a variety of clay 

 ironstone. We frequently find in it traces of carbonized vege- 

 table matter, and in some places it contains thin veins and seams 

 of a beautiful coal approaching the state of anthracite. Many 

 of the beds, especially in the lower part of the series, are exten- 

 sively quarried, and form an excellent strong material for the 

 construction of piers, and for other architectural purposes. 



In the sections along the coast, there appears a very peculiar 

 coarse sandstone, provincially called dogger, at the bottom of the 

 whole formation, and resting immediately on the alum-shale. 

 This dogger in some places appears as a single bed ; in other 

 places it is subdivided into several well-defined beds. Generally 

 it is highly ferruginous, and often of a dingy red or ochreous 

 colour : in these cases it is frequently spht into distinct blocks 

 by cross fissures, which are coated over with thin ferruginous 

 lamina, and are filled with ochreous clay. Rarely it is of a green- 

 ish colour, and then resembles some of the ferruginous sands 

 which have their place under the chalk ; not unfrequently it 

 becomes so coarse as almost to pass into a conglomerate form. 

 Most of it effervesces with acids, and it is associated with some 



