406 APPENDIX H. 



The oldest rocks that have been noticed are : — 



(1) The ranges of rugged metamorphic rocks north of the 

 city of Marocco, and forming the northern boundary of the 

 plain, respecting the age of which, and the period of their 

 upheaval and metamori)hism, there is no evidence. 



(2) The interbedded porphyrites and porphyritic tuffs of the 

 Atlas, forming the backbone of the ridge, the age of which, and 

 of the grey shales with which they seem to be interbedded, is 

 also uncertain. 



(3) Mica-schists of Djebel Tezah, in the Atlas, south-west 

 of Marocco, pierced with eruptive porphyritic dykes, which may 

 be an altered condition of the vertical grey shales adjacent to 

 the interbedded porphyrites. 



These rocks are our starting point, respecting which there is 

 no evidence of their age, or even relative age. 



(4) "We now come to a long period of denudation of the 

 Atlas ridge, and its sculpturing into hill-and-valley contour, 

 before the deposition of the Red Sandstone and Limestone 

 series. 



(5) The deposition over what is now the Marocco plain, of 

 the Cretaceous Red Sandstone and Limestone series (and beds 

 possibly of Miocene age), which also occupies pre-existing valleys 

 in the older poi'phyrites of the Atlas. 



(6) The intrusion of diorite into the porphyrites and por- 

 phyritic tuffs, probably accompanied by a further elevation of 

 the Atlas range, disturbing the stratified Red Sandstone and 

 Limestone series, throwing them into a synclinal trough, from 

 which the beds rise northwards towards the plain, and south- 

 wards towards the Atlas. 



(7) A further long period of denudation of the Red Sandstone 

 and Limestone series, rescooping out the lateral valleys of the 

 Atlas, in continuation of the valleys that existed in the por- 

 phyrite ridge prior to their deposition, and also denuding the 

 beds in the Marocco plain to the extent of at least 300 feet, 

 leaving isolated remnants as flat tabular hills rising above the 

 present general level of the plain. 



(8) A further jpossible emission of red porphjrrites through 

 the stratified beds of the plain, which may have been con- 

 temporaneous with the eruption of the red porphpy dykes 

 of Djebel Tezah, in the High Atlas ; but I could not clearly 



