DEYING UP OF BATS AND SALT LAKES. 



185 



whose composition and nacreous appearance seem as if they ought to 

 be attributed to guano saturated with salt water.* 



This construction of new shores, either by the sea itself or by the 

 coral animals, like the gradual formation of the dunes, results in 

 completely modifying the form of the coast, by separating from the 

 rest of the sea large bays, which the rapid evaporation transforms 

 later into firm land. It is thus that on the eastern coast of Africa 

 the small Lake of Bahr-el-Assal, at the extremity of the Gulf of Ted- 

 jura, has been separated from the sea by a slender ridge of sand, and 

 dried up under the rays of the sun. Kain-water being very rare in 

 this country^ and the basin receiving no affluent, its waters have not 



Fig. 83— Bahr-el-Assal and the Gulf of Tedjura. 



been replaced, and now it is only a marshy hollow, the level of 

 * Darwin, Volcanic Islands, p. 49, and following. 



