GEOLOGY OF MAROCCO AND GREAT ATLAS. 467 



ascertain whether these bosses really pierced the stratified beds, 

 or were existing before their deposition. 



(9) A post-Cretaoeous eruption through the Red Sandstone 

 and Limestone series of a multitude of dykes of amygdaloid 

 basalt, the age of which is uncertain. 



The more recent changes commence with : — 



(10) The formation of gigantic boulder-beds flanking the 

 northern escarpment of the Atlas plateau, and spreading doMii 

 in great mounds and undulating ridges from a height of 3,900 

 feet to the borders of the plain, 1,900 feet above the sea, with a 

 range in vertical height of about 2,000 feet, and extending up 

 the entrances of several of the lateral valleys, as well-defined and 

 symmetrical moraines. 



(11) The formation of moraines at the heads of the Atlas 

 valleys, commencing at a height of 5,800 feet, and spreading up 

 to the clifis of the Atlas ridge, to a height of between 7,000 and 

 8,000 feet, with a terminal angle of repose 850 feet in vertical 

 height. 



(12) The formation of a plain of shingle behind the mo- 

 raines, at a height of about 6,700 feet, which seems to be the 

 bed of a small lake. 



(13) The recession and extinction of glaciers in the Atlas 

 range, on which there is now not even perpetual snow. 



(14) An elevation of the coast-line of at least 70 feet, repre- 

 sented by the height of the raised beaches of concrete sand at 

 Mogador and other parts of the coast, which may possibly be 

 contemporaneous with the elevation of similar raised beaches 

 on the coasts of Spain and Portugal, and with the raised beaches 

 of our south-western coast. 



(15) A slight subsidence of the coast-line, now going on, 

 with an accumulation of extensive deposits of blown sand at 

 Mogador. 



(16) The formation of a tufaceous surface-crust over almost 

 the entire plain of Marocco, due to the drawing up to the 

 surface, by rapid evaporation, of water from the subjacent 

 calcareous strata, depositing, layer by layer, laminated car- 

 bonate of lime. 



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