SUPPLEMENTARY NOTES. 465 



seems to point at an agent which may have produced many of the 

 metallic sulphurets. See vol. ii. P. 108. Note. 



In a subsequent communication to the Geol. Soc. of London, 

 January, 1837, Mr. Fox observes, " I imagine that I see more and 

 more reason to believe, that the Eastward and Westward ten- 

 dency of metallic veins, must be ascribed to the electro-magnetic 

 influence of the earth. In some parts of the world there may be 

 considerable deviations from this bearing, which may be owing 

 to local circumstances; but the coincidence in their direction, 

 generally speaking, is so great and decided as clearly to indicate 

 the operation of a general law. It is worthy of remark that many 

 of the large veins of haematite, and other varieties of the oxide of 

 iron found in Cornwall, have nearly a N. &; S. bearing. I am not 

 prepared to say whether there are any exceptions, or not; but it is 

 curious to find decided iron veins nearly coincident with the mean 

 magnetic meridian," 



M. Becquerel has recently made a most important application of 

 some electro-chemical apparatus to the immediate reduction of the 

 ores of silver, lead, and copper, without the intervention of mercury, 

 and is now occupied with farther researches on the extraction of 

 metals from their respective ores. L'Institut. March 21, 1836. 

 Phil. Mag. February, 1837. 



The practical results of these researches are noticed in the 

 following terms by Mr. Wheatstone, in a letter I have recently 

 received from him upon this subject. " The value of Mr. Fox's 

 interesting experiments consists in the exact analogy they bear 

 to the circumstances which actually take place in mineral veins; 

 still more important are the long-continued researches of M. 

 Becquerel, on the permanent action of feeble currents in effecting 

 chemical combinations and decompositions; a very full account of 

 these instructive experiments has recently been published in the 

 third part of Taylor's Scientific Memoirs, and deserves the atten- 

 tion of every geologist who desires to penetrate into the mysteries 

 of mineral formations. Neither are these investigations without 

 practical value; M. Becquerel has recently shown a mode by which 

 the precious metals may be separated from their ores, in a per- 

 fectly pure state, without the aid of mercury; and we understand 

 that the process is now actually working in some of the mining 



