Some Notes of Africa. 37 



plain of shifting sands by any means, but a hot, dry, barren region 

 with much variety of surface. The eastern portion is depressed 

 often below the general level, and covered in part with a hard but 

 brittle clay in place of sand; while the western portion consists in 

 large part of rocky plateaus sometimes rising into mountains. The 

 southern portion is represented as more uniform in character, but 

 of that we cannot speak from observation. 



The High Plateau, with gradient slopes both to north and south, 

 and exposed therefore to the sea winds upon the one hand and the 

 hot breath of the desert on the other, is of very doubtful char- 

 acter, both as to climate and productiveness. It is subject to great 

 extremes of heat and cold — being three to four thousand feet in 

 height in the central portion — and while it sometimes yields an 

 abundant vegetation, at other times it fails almost entirely. 



The Metija and Chelef plains are subdivisions of the Tell, 

 having a north and south rather than east and west direction, and 

 are most remarkable for a great depth of comparatively recent 

 deposit, evidently due to the winds blowing from the direction of 

 Sahara across depressions in the High Plateau. The depth of 

 recent deposit in the Metija plain — the lower part of which how- 

 ever consists of pebbles and gravel and cannot therefore be of 

 sub-ariel origin — is set down at five hundred to six hundred feet. 

 This presents a problem which as yet has not been solved. 



There is also a pecularity about many of the rivers of Northern 

 Africa, especially of Algiers. Most of them rise well up in the 

 regions of the High Plateau, and at the time of flood bear large 

 quantities of black and muddy water far out to sea, but at other 

 seasons have not force enough to reach the sea at all, but are 

 swallowed up in the sinks and marshes along the lower portion of 

 the Tell. 



Two points in Algiers have a special interest for the scientific 

 student. One lies near the borders of Tunis, the other well 

 toward the boundary of Morocco. 



On the way from an interior town to Bone upon the coast, we 

 came upon the springs of Hammam Meskoutin, which in a small 

 way reminded us of the Mammoth Hot Springs in the Yellowstone 

 Park. The water is almost up to the boiling point, and strongly 

 charged with lime, with a moderate percentage of iron. The 

 principal spring at present rises in a shallow cove upon the hill 

 side, and the deposit around is of almost snowy whiteness. The 

 water descending in tiny cascades is arrested here and there, by 

 little basins which immediately overflow and send their steaming 



