366 THE STORY-BOOK OF SCIENCE 



agreeable taste, although one cannot drink a glass of 

 salt water." 



4 * Doubtless; but in the waters of the sea it is ac- 

 companied by many other dissolved substances 

 whose taste is very disagreeable. The degree of salt 

 varies in different seas. A liter of w r ater in the 

 Mediterranean contains 44 grams of saline sub- 

 stances ; a liter of water in the Atlantic Ocean con- 

 tains only 32. 



"An attempt has been made to estimate, approx- 

 imately, the total quantity of salt contained in the 

 ocean. Were the ocean dried up and all its saline 

 ingredients left at the bottom, they would suffice to 

 cover the whole surface of the earth with a uniform 

 layer ten meters thick." 



"Oh, what a lot of salt!" cried Emile. "\Yc 

 should never see the end of it, however much we 

 salted our food. Then salt is obtained from the 

 sea?" 



"Certainly. A low, level stretch of seashore is 

 selected, basins are dug, shallow but of considerable 

 extent ; these are called salt marshes. Then the sea 

 water is admitted to these basins. When they are 

 full, the communication with the sea is closed. The 

 work on salt marshes is done in the summer. The 

 heat of the sun causes the water to evaporate little 

 by little, and the salt remains in a crystalline crust 

 that is removed with rakes. The accumulated salt 

 is piled up in a big heap to let it drain. " 



"If we should put a plate of salt water in the sun, 

 would that be doing in a small way what is done in 

 the salt marshes?" asked Jules. 



