418 THE CHEMISTRY OF CREATION. 



phuric and carbonic acids, enter into the com- 

 position of sea-water. Of the four elements, 

 thus united, calcium in a state of nature exists 

 as a sulphate and carbonate. Sulphate of lime 

 is soluble in 500 parts of water, and carbonate 

 of lime is sparingly soluble in water contain- 

 ing carbonic acid is, in fact, never absent 

 from either river or spring water, constituting 

 what is called the " hardness " of such waters. 

 All the salts of soda and potash are highly 

 soluble. Thus, from a review of the main 

 constituents of our globe, it would appear 

 natural to expect that the water which sur- 

 rounds so large a portion of it, and is the 

 greater reservoir for its water-shed, would con- 

 tain sodium, potassium, calcium, and magne- 

 sium, in combination : and such is actually the 

 case. Why chlorine and sulphuric acid are the 

 principal bodies united to these elements, it is 

 difficult to say. Sulphuric acid, it is true, in 

 the form of sulphate of lime or gypsum, forms 

 a large constituent of the earth's crust; but 

 chlorine is chiefly known in nature as in union 

 with the sodium of sea-water. The cause 

 of its preponderance is, therefore, buried in 

 obscurity. 



When we come to ask, again, the cause of 

 the constancy of the relative proportions of 

 these ingredients in sea-water, a fresh per- 



