Detrital Theory of Geology. 305 



by far the greatest abundance, magnesia the next in 

 frequency, and potash the least ; neither is this order of 

 amount or frequency changed when the tertiary formations 

 are carefully considered. 



For if the chief elements or earths were arranged in the 

 order of frequency or quantity in the granite, and then the sedi- 

 mentary rocks, they would stand pretty nearly in the follow- 

 ing order : in granite silicon, alumina, potash, magnesia, 

 iron, soda, and lime, would represent the relative amount of 

 the component parts, commencing with silicon as the most 

 abundant, and lime as the least ; whilst in the sedimentary 

 rocks the arrangement of the constituent parts being made 

 in the order of frequency or amount, the following would 

 obtain : silicon most abundant, alumina and lime nearly 

 equal, and magnesia, iron, soda, and potash much less 

 abundant. 



After a careful consideration, by the data supplied, of the 

 component parts of the sedimentary and granitic rocks, 

 though there is no certain measure, it is probably not far from 

 the truth to estimate lime in granite as about 3 per cent., and 

 in the sedimentary 16 or 17 per cent. If such, then, be an 

 approximation to the actual relation of lime as contained in 

 the two kinds of rocks plutonic and sedimentary whence 

 is it that such a contrast in the quantity of LIME should 

 exist, when one is derived in part or entirely from the 

 other ? In the mode in which the matter is here put, it will 

 be said, nothing can be admitted which does not involve the 

 absurdity, that the effect is greater than the cause. There- 

 fore, for the better appreciation of this important subject, 

 one or two of the usually supposed sources of LIME will be 

 examined. 



As, before there were rivers, the mighty ocean appears to 

 have washed over or rested upon ALL rocks, so in its waters 

 will be found all the soluble salts not reduced to an insoluble 



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