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LETTERS FROM 
assigned for this current, is the great loss of 
water occasioned by the absorption of the 
vast sandy deserts on the northern coast of 
Africa. No doubt these deserts are thirsty 
enough, and they may imbibe and evapo¬ 
rate a great quantity of water; but the 
same difficulty occurs here as before,—what 
becomes of the solid matter ? It would 
either be deposited in the Mediterranean, or 
the continent of Africa would, in every 
two or three hundred years, receive an in¬ 
crease equal in bulk to the whole contents of 
that sea. 
Perhaps such considerations as these may 
have led the inquirers into the cause of this 
phenomenon to conclude that the Mediter¬ 
ranean must have an outlet somewhere, by 
which the prodigious quantity of water 
poured in through the Straits may be again 
discharged. I leave the rivers out of the 
