454 APPENDIX H. 



scarped faces are produced by the violent westerly gales blowing 

 the sand up the angle of repose, and accumulating it in foun- 

 tain-like showers over the rounded backs of the sand-hill 

 ranges. 



It is worthy of note that the sub-aerial ripple-markings 

 superimposed on the greater undulations, occupy a reversed 

 position with reference to the prevalent winds, their long side 

 facing the wind, with the more vertical straight scarps on the 

 lee side. The moving sand in this case is drifted up the long 

 side, and falls over the scarp at the angle of repose. 



The Plain of Marncco. — We now turn inland ; and before 

 referring to the details of the structure of the Great Atlas 

 range, it will save repetition if I briefly describe the general 

 contour of the district under consideration. Leaving the sand- 

 hills, which die out inland, and travelling westward, we gradu- 

 ally ascend over an undulating country, in aspect somewhat 

 like the Weald of Sussex, covered for 30 miles with Argan 

 Forest, till we reach, at 60 mUes inland, the average level of 

 the plain, about 1,700 feet above the sea. 



The fundamental rock is here rarely to be seen ; for the entire 

 face of the country is shrouded over by a sheet-like covering of 

 tufaceous crust (fig. 3), rising over hill and valley, and following 

 all the undulations of the ground. Only in river-beds and 

 here and there by the side of a hill were the fundamental beds 

 visible, and seen to consist of alternations of hard and soft 

 cream-coloured calcareous strata, dipping and undulating in 

 various directions at low angles, and so closely resembling the 

 surface crust that it was difficult to distinguish the one from 

 the other, unless the surface crust happened to lap unconform- 

 ably over the scarped exposures of the stratified beds. This 

 singular deposit varies in thickness from a few inches to two or 

 three feet, and is taken advantage of by the Moors for the ex- 

 cavation of cellars in the soft ground, over which the crust 

 forms a strong roof. Thes9 are termed maiamoras, and are 

 used for the storage of grain, and as receptacles for burying the 

 refuse from the villages. The calcareous crust in the neigh- 

 bourhood of Marocco is extensively burned for lime. In section 

 it presents a banded agatescent structure, often much brecciated. 

 It is impossible it can have been deposited by any waterflow, as 

 completely isolated hills are shrouded over by it as ttiipkly as the 



