XII.] ORIGIN OF METALLIFEROUS DEPOSITS. 235 



Let us now consider the beneficent results of the process 

 of vein-making. The precious metals, such as silver, are so 

 sparsely distributed, that even the beds rich in the products of 

 decaying sea-weed, which we have supposed to be deposited 

 from the ocean, would contain too little silver to be profitably 

 extracted. But in the course of ages these sediments, deeply 

 buried, are lixiviated by permeating solutions, which dissolve 

 the silver diffused through a vast mass of rock, and subse- 

 quently deposit it in some fissure, it may be in strata far above, 

 as a rich silver-ore. This is nature's process of concentration. 



We learn from the history which we have just sketched the 

 important conclusion, that amid all the changes of the face of 

 the globe the economy of nature has remained the same. We 

 are apt, in explaining the appearances of the earth's crust, to 

 refer the formation of ore-beds and veins to some distant and 

 remote period, when conditions very unlike the present pre- 

 vailed, when great convulsions took place, and mysterious forces 

 were at work. Yet the same chemical and physical laws are 

 now, as then, in operation : in one part dissolving the iron 

 from the sediments and forming ore-beds, in another separating 

 the rarer metals from the ocean's waters j while in still other 

 regions the consolidated and buried sediments are permeated 

 by heated waters, to which they give up their metallic matters, 

 to be subsequently deposited in veins. These forces are always 

 in operation, rearranging the chaotic admixture of elements 

 which results from the constant change and decay around us. 

 The laws which the First Great Cause imposed upon this 

 material universe on the first day are still irresistibly at work 

 fashioning its present order. One great design and purpose is 

 seen to bind in necessary harmony the operations of the min- 

 eral with those of the vegetable and animal worlds, and to 

 make all of these contribute to that terrestrial circulation 

 which maintains the life of our mother earth. 



While the phenomena of the material world have been 

 looked upon as chemical and physical, it has been customary 

 to speak of those of the organic world as vital. The tendency 

 of modern investigation is, however, to regard the processes of 





