SUN AND WIND IN LANDS OF INFREQUENT RAINS 199 



A 



been overflowed by its waters. The Sawa Lake in the Persian 

 Desert, which disappeared some five hundred years ago, again 

 came into existence in 1888 so as to cover the caravan route to 

 Teheran. 



The record in the rocks of the distant past reveals the fact that 

 in some former deserts barriers were, in the course of time, broken 

 down, with the result that an invading 

 sea entered through the breached wall. 

 The result was the sudden destruction 

 of land life, the remains of which are 

 preserved in " bone beds," now covered 

 by true marine deposits. A still later 

 episode of the history was begun when 

 the sea had disappeared and land ani- 

 mals again roamed above the earlier 

 desert. Such an alternation of marine 

 deposits with the remains of land plants 

 and animals in the. deposits of the Paris 

 Basin, led the great Cuvier to his belief 

 that geologic history was comprised of 

 a succession of cataclysms in which life 

 was alternately destroyed and re-created 

 in new forms a view which later, under 

 the powerful influence of Lyell and 

 Darwin, gave way to that of more 

 gradual changes and the evolution of 

 life forms. 



Some characteristics of the desert 

 wastes. The great stretches of the 

 arid lands have been often compared to 

 the ocean, and the Bedouin's camel is 

 known as " the ship of the desert." Though a deceptive resem- 

 blance for the most part, the comparison is not without its value. 

 Both are closed basins, and it is in this respect that the desert and 

 the ocean may be said to most resemble each other, for none of 

 the water and none of the sediment is lost to either except as 

 boundaries are, with the progress of time, transposed or destroyed. 

 Flatness of surface and monotony of scenery both have in common,- 

 and the waters and the sand are in each case salt ; yet the ocean, 



FIG. 206. Map of the former 

 Lake Bonneville (dotted 

 shores), and the boundaries 

 of the Great Salt Lake of 

 1869 (smaller area) and that 

 of the present (after Berg- 

 haus). 



