458 APPENDIX H. 



by the summer heat ; and we came to the conclusion that there 

 was nothing like perpetual snow on any portion of the chain we 

 visited, included in the section (apparently the highest part) 

 lying due south of the city of Marocco. 



As seen from the city, the great ridge appears to rise abruptly 

 from the plain some 25 miles off; and so deceptive is the dis- 

 tance, that it looks as though it were a direct ascent from the 

 plain to the snow-capped summit, even too steep to scale ; but 

 in reality this wall-like ridge represents a horizontal distance of 

 15 miles or more from the foot to the summit. As we ap- 

 proached it, an irregular plateau four or five miles wide was 

 seen to form a sort of foreground to the great mass of the chain, 

 from 2,000 to 3,000 feet above the plain, and 4,000 to 5,000 

 feet above the sea-level. This is intersected by occasional narrow 

 ravines, which wind up to the crest of the ridge ; and its face, 

 fronting the plain, is for the most part exposed as an escarpment 

 of red sandstone and limestone beds dipping away from the plain, 

 and again rising from a synclinal against the crystalline porphy- 

 rites of the centre of the ridge, and unconformably overlying 

 nearly vertical grey shaly beds with a strike ranging with the 

 general trend of the Atlas range. Against the plateau escarp- 

 ment rest enormous mounds of boulders spreading down to the 

 level plain. 



These, then, are the general features of the chain of the 

 Atlas and plain of Marocco, the further details of which it will 

 be convenient to consider under the following heads : — 



(a) Surface Deposits and Boulder Beds. 

 (6) Moraines of the higher valleys, 



(c) Stratified Red Sandstone and Limestone Series. 



(d) Grey Shales. 



(e) Metamorphic Bocks. 

 (/) Porphyrites. 



(g) Eruptive Basalts. 



(a) Surface Deposits and Boulder-beds. — Next to the Tufa 

 crust already described, which extends over almost the entire 

 plain of Marocco, perhaps the most remarkable feature in the 

 physical geology of the country is the enormous deposit of 

 boulders that occurs in the lateral valleys, and flanks the great 

 chain on its confiiics with the plain. Of marine drift there is 



