36 Some Nofes of Africa. 



Trappean hills, are points which as yet cannot be certainly deter- 

 mined. Also whether there was a single period of disturbance in 

 which ashes and bombs appeared, or more than one, is a question 

 that awaits further investigation. The disposition of the explorer, 

 and even of the casual visitor, now will be to look out for the 

 crater from which the material of the ash-beds came. It may be 

 concealed beneath a considerable depth of rock or soil, in which 

 case the discovery will probably be purely accidental ; still this 

 will be an item of interest until the point is located and the vent 

 if possible is found. 



Some Notes of Africa. 



In lieu of other matter, we venture to append a few notes made 

 in Northern Africa in May last, touching certain geological fea- 

 tures of that country. 



In the first place it may be stated in general terms, that the 

 northern coast of Africa, west of La Calle, is a series of head- 

 lands, with occasional intervening spaces sloping to the sea, and 

 with frequent indentations in the coast, that went far to adapt it to 

 the uses of the Turkish corsairs and the Algerine pirates, of which 

 the world has heard so much. Further, the, interior country, 

 especially in Algiers, is divided into three well defined belts, or 

 regions parallel to the sea and extending southward into the 

 desert. They are known respectively as the Tell, the High 

 Plateau, and the Desert border. 



The Tell is an undulating plain lying immediately back of the 

 headlands that mark the coast, and extending from fifty to eighty 

 miles in width, with a length east and west of perhaps seven hun- 

 dred miles. It is almost uniformly fertile and large portions of it 

 are under cultivation. It is traversed in the eastern portion by a 

 spur of the Atlas Mountains and has also considerable areas of bog 

 or swamp. 



The High Plateau consists of a series of benches or terraces, 

 lying nearly parallel to the Tell upon the one hand, and the 

 desert on the other, and sloping from a central ridge in both 

 directions. Then comes the desert of Sahara — not an interminable 



