456 APPENDIX H. 



we were told of great beds of shingle covering the plain, and 

 fully anticipated some interesting drift phenomena; but these 

 shingle-beds were found to be nothing more than the broken 

 debris of the surface tufa, covering the plain for hundreds of 

 square miles with stony fragments. Of marine drift there is 

 not a vestige, the few isolated patches of waterworn stones and 

 alluvial shingle being always connected with river valleys, ex- 

 cepting only the huge boulder deposits of the Atlas hereafter to 

 be referred to. 



About midway between Mogador and the city of Marocco, 

 the monotony of the plain is broken by a curious group of flat- 

 topped hills, which rise two or thr'ee hundred feet above its 



' Camel s Back,' flat-topped hills m the Plain of Marocco. 



general surface. They present straight scarped sides, on which 

 are exposed cream-coloured calcareous strata capped with a flat 

 tabular layer of chalcedony, which seems, in arresting denuda- 

 tion, to have determined their peculiar and symmetrical form. 

 In these we found no fossils ; and I am doubtful whether they 

 are an inland extension of the Miocene beds observed by Dr. 

 Hooker at the ' Jew's Cliff,' near Saffi, or are some members of 

 the Cretaceous series, of which there are sections on the coast 

 north of Saffi and on the flanks of the Atlas. 



At this point the main boundaries of the plain come into 

 full view,— on the north a rugged range of mountains trending 

 east and west, which we estimated at from 2,000 to 3,000 feet 

 in height ; and on our right the great chain of the Atlas, rising 

 11,000 feet above us and between 12,000 and 13,000 feet above 



