39 
The distance between the beds is commonly about 
two feet, and this space is filled with a sort of white and 
not very hard clay, which taking the same direction, 
forms intermedial beds of a slaty texture. These beds 
of granite and clay are very little above the level of the 
sea; their highest point does not exceed thirty or forty 
feet; but their width is considerable, for they are exactly 
the same at the river of Tetuan, and at eight leagues 
distance.* I have also remarked some beds of granite 
advancing into the sea to a great distance, and taking 
the same direction. 
If ^were permitted to draw large inferences from 
small tacts, I might say that the catastrophe which open- 
ed the Streights of Gibraltar was occasioned by a sud- 
den sinking, not of the ground, which forms the bottom 
of the streight, but of that part which is nearest on the 
south, and on the vacancy of which fell the mountain or 
earthy mass which formerly occupied the space that is 
now filled by the arm of the sea. In consequence of 
this movement the perpendicular beds of granite have 
taken their actual direction; but on the other side, as 
this compact granite seems to be of a secondary format 
tion, we may admit all the possible directions in the 
beds, without supposing any derangement posterior to 
their formation. 
On this bed or general basis of the coast, the waves 
and the wind have accumulated other beds, of soft clay 
and of sand; they form the hills and the high mountains 
of the road to Tetuan. The vegetable and animal re- 
mains have made a bed of vegetable earth which covers 
the whole, and is extremely fertile. 
At the southern parts of the bay of Tangier, on the 
sea shore, the easterly winds have formed by degrees, 
great accumulations of sand; they represent already 
