86 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Jan. 10, 



companying Dr. Hooker to Morocco and the Great Atlas, permission 

 for our visit having heen obtained from the Sultan through repre- 

 sentations made to the Moorish Government by Lord Granville 

 through Sir John D. Hay, our Ambassador at Tangier. 



The object of the journey was mainly botanical ; and as an en- 

 gagement was given by Dr. Hooker that we should not collect mine- 

 rals, the opportunities for geological investigation were very limited. 

 The observations I was able to make on the structure of the 

 great chain, which had not been previously ascended by a European, 

 and of the Plain of Morocco, are embodied in the accompanying sec- 

 tion (PI. III. fig 1). Stopping for about a fortnight at Tangier, we 

 made several excursions in the neighbourhood. The western part of 

 the northern promontory of Morocco, facing the Straits of Gibraltar, 

 consists of highly contorted beds of hard courses interstratified with 

 brindled yellowish sandstones and variegated puce and grey marls, 

 having a general dip to the south-east, but so twisted about that the 

 dip and strike are often reversed within a few feet. The country has 

 a general undulating contour, here and there rising up into ridges of 

 from 2000 to 3000 feet, in which the hard bands weathered out from 

 the softer strata are strikingly prominent from a great distance. 



There is no palseontological evidence of their age ; but, judging 

 from their resemblance to the cliff- sections near Saffe, in which 

 fossils occur, they are presumably Neocomian or Cretaceous. 



The eastern half of the northern promontory, including Tetuan 

 and Ape's Hill, facing Gibraltar, consists of beds of a different 

 character, for the most part of a hard metamorphic limestone in 

 which dip and strike are very obscure : these may be a southern ex- 

 tension of the Gibraltar limestone ; but I had no opportunity of 

 tracing the connexion to Tetuan. 



The Tetuan limestone has given rise to enormous beds of bree- 

 ciated 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 calcareous sheet, to which I shall have occa- 

 sion further to refer, which shrouds over the entire plain of Morocco. 

 Pespecting 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 in continuity with 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 abun- 

 dant evidence. The more recent seem to be, first, an elevation of 

 from 60 to 70 feet along the entire coast, imphed 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 upturned edges of nearly 



