GEOLOaY OF MAROCCO AND GREAT ATLAS. 449 



divides them into four stages, characterised respectively by 

 marls, dolomites, a calcareous sandstone with the odour of 

 petroleum, and a lithographic limestone containing siliceous 

 concretions. I am of opinion that the Tetuan series, ranging 

 with the Gibraltar limestone, and probably extending far to the 

 south, is separated from the more recent Cretaceous series to 

 the west and north-west by a great north and south fault, 

 which divides nearly equally the Tangier promontory. M. 

 Mourlon, referring to some specimens of shelly limestone in the 

 Brussels Museum, collected near the river Mhellah in the 

 district of Ouled Eissa, between Fez and Tetuan, resembling 

 the Muschelkalk in aspect, and associated with beds resembling 

 those at Tetuan, considers that they may also be of Jurassic age. 



The Tetuan limestone has given rise to enormous beds of 

 brecciated tufa, on terraces of which the city is built. The 

 flow seems to have taken place from the hills to the north-west 

 of the city, and has produced beds of a collective thickness of 

 60 or 70 feet. This is evidently true tufa, due to aqueous 

 deposition, and is of a different character from the great cal- 

 careous sheet, to which I shall have occasion further to refer, 

 which shrouds over the entire plain of Marocco. 



Eespectiug the Mediterranean coast-line of Barbary, I will 

 not add much to a paper read before the British Association at 

 Liverpool, in which I remarked on the singular absence of 

 coast-cliffs of any height. The undulating contour of the land- 

 surface extends down to the water's edge, a continuation of the 

 form of the bottom of the straits without the intervention of 

 cliff-escarpments, from which I surmised that the present sea- 

 level and coast-line of the straits had not been of long duration. 



Of frequent changes of level on the Barbary coast there is 

 abundant evidence. The more recent seem to be, first, an 

 elevation of from 60 to 70 feet along the entire coast, implied 

 by the existence of concrete sand-cliffs with recent shells exactly 

 similar to the raised beaches of Devon and Cornwall. These 

 occur in Tangier Bay to a height of 40 feet, resting on the up- 

 turned edges of nearly vertical mesozoic beds ; to the south of 

 Cape Spartel, as a long cliff nearly 50 feet high ; as low shoals 

 near Casa Blanca ; as a compact cliff about 50 feet high at 

 Saffi, and as a coast-cliff and islands at Mogador, where the 

 concrete sand-beds attain a height of 60 or 70 feet above the 



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