INEXHAUSTIBILITY OF COMMON SALT. 2. ^ 25 



oceans, and tlie evaporation is probably not so great on an average 

 as in the Indian Ocean. But nevertheless the Gulfs of the Indian 

 Ocean present phenomena analogous to those of the inland seas of 

 the Atlantic. Thus the Red Sea, into which no single permanent 

 stream of water flows, and where evaporation proceeds with very great 

 intensity, shows the enormous degree of saltness of 43 thousandths ; 

 such a proportion as is only found in inland salt-water lakes.* 



Chloride of sodium or common salt contributes, as we have said, 

 three quarters of the saltness of sea water : this is indeed the cha- 

 racteristic salt of the ocean which most of all gives it its peculiar 

 flavour, and that odour with which the sea-breezes, laden with the 

 fine spray of the waves, are charged. The air which rests on the sea 

 also contains salt to a considerable height; at an elevation of 2,000 

 feet above the coast on the sides of the mountain which towers above 

 the Peruvian town of Iquique, Mr. Bollaert asserts that any materials 

 washed in distilled water are covered in a few days by a slight 

 incrustation of salt.f 



The thickness which a layer of chloride of sodium in the open 

 sea would form if crystallized, would be on an average nearly two 

 inches to every fathom of water, so that if one could imagine the 

 entire evaporation of the waters of the ocean, estimating them to 

 be on the average above three miles deep, there would remain at the 

 bottom of its bed a layer of salt of about 230 feet in mean thick- 

 ness, which would represent for the whole extent of the seas more 

 than a thousand millions of cubic miles. We can understand how, 

 with such vast quantities of chloride of sodium in solution, the sea 

 has been sufficient to form those enormous beds of rock-salt that 

 are found in the earth in various parts of Europe, without reckon- 

 ing many other deposits which still remain to be discovered, and 

 which, sooner or later, will be revealed to us by the labours of 

 miners, or by Artesian borings. 



Then, too, we may see the ocean at work on all the low coasts, 

 where it deposits saline beds, destined to become in process of time 

 masses of rock-salt, after they shall have been buried beneath more 

 modern strata. When, in consequence of a tempest, or of a high tide, 

 the waters of the ocean are spread in a thin sheet over a flat shore, 

 or in some deeper depression, this slight bed of salt water, spread 

 over a vast surface, evaporates rapidly under the rays of the sun, and 

 leaves in its place a slight white crust of saline crystals. Other 



♦ Forchhammer, Tlnlosophical Transactions, parti. 1865. 

 t Antiquities, p. 258. 



