238 ORIGIN OF METALLIFEROUS DEPOSITS. [XII. 



Wurtz, Genth, and Selwyn as to the solution and re-deposition of 

 gold in modern alluvial deposits, seem to be well-grounded, and we 

 are led to the conclusion that the circulation of this metal in nature 

 is as easily effected as that of iron or of copper. The transfer of 

 certain other elements, such as titanium, chrome, and tin, or at least 

 their accumulation in concentrated forms, appears, on the contrary, 

 to require conditions which are no longer operative, at least at the 

 surface of the earth. 



It should here be noticed, that Professor Henry Wurtz of New 

 York, in a paper read before the American Association for the Ad- 

 vancement of Science in 1866, and published in the Journal of 

 Mining in 1868, expressed the opinion that the ocean-waters con- 

 tain gold, and urged experiments for its detection. According to 

 his calculations, the total amount of gold hitherto extracted from 

 the earth, and estimated at two thousand million dollars, would 

 give only one dollar for two hundred and eighty million tons of 

 sea-water ; while from the experiments of Sonstadt it would appear 

 that the same quantity of gold is actually contained in twenty-five 

 tons of water. 



