THE WAR IN THE OCEAN. 225 



Now some of these resulting compounds were soluble, and 

 remained dissolved in the sea-water. Such were the chlorides 

 and sulphates, and the carbonates of potash and soda. Thus 

 the water of the primitive ocean became charged with 

 sulphate of soda, which is Glauber's salt; sulphate of 

 lime, which is gypsum ; sulphate of magnesia, which is 

 Epsom salts; also with chloride of sodium, which is common 

 salt ; and the other chlorides, which are the bitter impurities 

 in the sea. 



But others of the resulting compounds were but little 

 soluble, and were therefore precipitated to the bottom; what were 

 they? Carbonate of lime and carbonate of magnesia. The 

 first is limestone, and the second is generally mixed with the 

 first, forming dolomite. That is, a layer of calcareous material I 

 was spread over the sea-bottom. It was a chemical precipitate, 

 not a sediment in the geological sense. Two other constituents 

 were added to the material spread over the bottom. I stated 

 above that the primitive crust contained silica and alumina ; 

 what became of these when the original partners had to sunder 

 connections? Potash, soda, lime, magnesia we have traced to 

 their destinations ; but silica and alumina are left outstanding. 

 Now, probably, these concluded to form a partnership for 

 themselves; and so silicate of alumina resulted. This being 

 insoluble, must have fallen to the bottom. It may have 

 mingled, in some places, with the calcareous precipitates and 

 it may in other places have been bedded by itself. In the 

 latter case, beds of argillite would result. With the silica and 

 alumina some potash may in other cases, have combined ; and 

 thus would be formed a mineral known as potash feldspar, or 

 common feldspar. If soda or lime, instead of potash, united 

 with the silica and alumina, the result was simply another 

 species of feldspar. The feldspars are very abundant in the 

 oldest rocks. 



But perhaps, again, some of the outstanding silica and 

 alumina concluded not to combine together. Then the alumina 

 would simply remain free alumina, to mix with any of the 

 other compounds produced, or form by itself a bed of pure 



