70 CLIMATE AND EESOURCES OP 



than the ocean. These seas have no outlet, and the greater 

 amount of salt in their waters is the result of evaporation of 

 the water brought down to them, the salts brought down in 

 the water from the drainage basin of the rivers pouring into 

 them being left behind. The two former seas are below the 

 sea-level. The same is the case of inland lakes, many of 

 which are considerably above the sea-level, but which have 

 no surface exit for the water brought to them, and which is 

 lost by evaporation. The percentage of saline matters in 

 these inland seas and lakes is greater than in the ocean. 



There are many cases of land which being under water 

 during the rainy seasons, dries up, and is covered with a 

 saline incrustation during the dry weather. These are tem- 

 porary shallow lakes, which lose their water in the hot 

 seasons by evaporation, the salts being left behind when the 

 water is evaporated. 



Where these salt lakes and plains are below the level of 

 the sea, their existence there is said to be due to a subsidence 

 of the crust of the earth ; and where above the sea-level, they 

 are considered to be the beds of ancient seas, elevated by 

 upheaval. Is this true in every case ? May it not be that in 

 many cases these salt lakes and plains below the sea level are 

 the result of evaporation ? Should the amount of water lost 

 by evaporation from a lake exceed the amount supplied to it 

 from its drainage area, the area of the lake would contract 

 till an equilibrium was established between the amount of 

 water received by drainage and that expended by evapora- 

 tion. In the case of plains which dry up, there can be no 

 excess of evaporation over amount of water supplied ; the last 

 drop of moisture is dried up, and there the matter ends till there 

 is a fresh supply. Where salt plains occur above the sea- 

 level they may be the result of the gradual elevation of the 

 land by silt brought down from higher lands. The accumu- 



