1872.] MAAV — PLAIN OF MOEOCCO. 89 



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 unconformably 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 excavation of cellars in the soft ground, over which the crust 

 forms a strong roof. These are termed matamoras, and are used for 

 the storage of grain, and as receptacles for burying the refuse from 

 the villages. The calcareous crust in the neighbourhood of Morocco 

 is extensively burned for lime. In section it presents a banded 

 agatescent structure, often much breeciated. It is impossible it 

 can have been deposited by any waterflow, as completely isolated 

 hills are shrouded over by it as thickly as the valley-bottoms ; and 

 the only satisfactory explanation of its origin I can suggest is, that 

 it results from the intense heat of the sun rapidly drawing up 

 water charged with soluble carbonate of lime from the calcareous 

 strata, and drying it, layer by layer, on the surface, till an accumu- 

 lation several feet thick has been produced. The rapid alternation 

 of heavy rains and scorching heat which take place in the Morocco 

 Plain are conditions favourable to this phenomenon, which is un- 

 known in temperate climates. 



A familiar illustration of the same kind of action is seen in what 

 brickmakers term " limewash." A brick formed of marl containing 

 soluble carbonate of lime, if rapidly dried or placed in the clamp in 

 a wet state, will have on its upper surface, after burning, an unsightly 

 white scum or crust, by the accretion of soluble matter driven up- 

 wards and outwards by the quick evaporation. Before we left 

 Mogador on our journey inland, we were told of great beds of 

 shingle covering the plain, and fully anticipated some interesting 

 drift-phenomena ; but these shingle-beds were found to be nothing 

 more than the broken debris of the surface-tufa, covering the plain 

 for hundreds of square miles with stony fragments. Of marine 

 drift there is not a vestige, the few isolated patches of waterworn 

 stones and alluvial shingle being always connected with river- 

 valleys, excepting only the huge boulder-deposits of the Atlas here- 

 after to be referred to. 



About midway between Mogador and the city of Morocco the mo- 

 notony of the plain is broken by a curious group of flat-topped hills 

 (woodcut, fig. 1), which rise two or three hundred feet above its general 

 surface. They present straight scarped sides, on which are exposed 

 cream-coloured calcareous strata capped with a flat tabular laj^er of 

 chalcedony, which seems, in arresting denudation, to have deter- 

 mined their peculiar and symmetrical form. In these we found no 

 fossils ; and I am doubtful whether they are an inland extension of 

 the Miocene beds observed by Dr. Hooker at the " Jew's Cliff," near 

 Saffe, or are some members of the Cretaceous series, of which there 

 are sections on the coast north of Saffe and on the flanks of the Atlas. 



At this point the main boundaries of the plain come into full 

 view, — on the north a rua-ffcd range of mountains trending east and 



