TRAVELS IN 
face, the quantity of sand upon it, and the number of shells 
buried in the sand, have been urged as the grounds for such 
a conjecture. If, however, such has been the case, and the 
retreat of the sea progressive, it must have been an incalcu- 
lable period of time since the two bays were united. I believe 
they never were, and the more I liave attended to this subject 
the more I am persuaded that, instead of the isthmus ever hav- 
ing been covered with the sea, the time is yet to come when 
that event will take place. The surface is from twenty to 
thirty feet above the level of high watermark ; the sand upon 
it, except where it is drifted into ridges, is seldom three feet 
deep, and rests upon sand-stone or hard gravel. Ridges of 
blue schistus and granite rocks appear on various parts of the 
surface so elevated. Admitting, what is scarcely possible, 
that the sand-stone and the gravel were the fragments of the 
motmtains by which this plain is enclosed on two sides, yet 
neither the schistus nor the granite could have been adventi- 
tious ; these two materials must have been primeval, and 
they abound on the most elevated as well as on the lower 
parts of the isthmus ; in situations that cannot be less than 
one hundred feet above the level of the sea. But if we sup- 
pose the sea to have retreated one hundred feet, in its perpen- 
dicular height, we must also suppose the whole continent of 
Africa to have been an island at the time that the Cape pro- 
montory was an island. Yet the isthmus of Suez, near three 
thousand years ago, was the same flat sandy isthmus, neither 
higher nor lower, in all probability, than at the present day. 
It may be expected that I should offer my reasons for sup- 
posing the sea to be gaining upon the land in Southern Africa. 
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