THE ULTIMATE SOURCE OF COMMON SALT. 



135 



VI. 



THE ULTIMATE SOURCE OF COMMON 

 SALT. 



When we see the surface of the earth to a great extent 

 bathed in a solution of common salt, and read of salt regions 

 and mines of rock salt as existing in every quarter of the 

 globe ; when we consider, moreover, the vast importance of 

 this salt in the economy of the life of our planet, whether 

 animal or plant life, we are naturally led to speculate as to 

 the source whence all this salt was originally derived, and 

 the methods, hardly less than providential, which have been 

 employed in its distribution. To this inquiry we mast 

 bring some little knowledge of chemistry, geology, and 

 practical salt manufacture. The latter especially is of great 

 use in explaining appearances which would otherwise prove 

 deceptive or obscure. Common salt, it is perhaps needless 

 to say, is chloride of sodium, composed of the two elements 

 chlorine and sodium, and termed in chemical nomenclature 

 sodic chloride. Let us first see what are the salt sources 

 now existing. If we examine the crust of the earth 

 analytically, we find it composed of a number of non-metallic 

 and metallic elements, as oxygen, silicon, aluminium, calcium, 

 magnesium, potassium, sodium, iron, carbon, sulphur, 

 hydrogen, chlorine, &c, &c, frequently repeated in different 

 combinations, but occurring in the order of frequency enumer- 

 ated above. It will be noticed that chlorine is comparatively 

 scarce, at the bottom of the list given, which contains the 

 principal earth-forming elements ; and although sodium is 

 plentiful enough, it may as well be said, at once, that the 

 only source of sodic chloride, or common salt, to be found at 



