332 ORIGIN AND DEVELOPMENT OE ORE-DEPOSITS. 



5. That a part of the earthy contents of veins, and more 

 especially silica or qnartz, was apparently accumulated in this 

 manner, and usually combined, more or less, with matter other- 

 wise deposited. 



6. That rocks, clay, &c., containing different saline solutions 

 and metalliferous substances, in contact with water charged in 

 many instances with other salts, were calculated to produce 

 electrical action ; and this action was probably much increased by 

 the circulation of the water, and differences of temperature ; but 

 more particularly by the existence of compressed and heated 

 water, metallic bodies, &c., at or near the bottom of the fissures. 



7. That since the water in the fissures containing metallic 

 or earthy salts was a conductor of electricity, especially when 

 heated, and in a very superior degree to the rocks themselves, it 

 is evident that in conformity with the laws of electro-magnetism, 

 the currents of (positive) electricity would, if not otherwise 

 controlled, pass towards the west, through such fissures as were 

 most nearly at right angles to the magnetic meridian at the time. 



8. That the more soluble metallic and earthy salts may 

 have been decomposed by the agency of such electric currents, 

 and the bases been thereby determined in most instances towards 

 the electro-negative pole or rock ; that tin, however, under these 

 circumstances, is only partly deposited at the electro-negative 

 and partly at the electric-positive pole, in the state of a peroxide ; 

 and that these properties of this metal seem to bear on its 

 positions in the lodes with regard to copper, being sometimes 

 found with it and sometimes distinctly separated from it. 



9. That the position of one rock with respect to another or 

 to a series of other rocks may, as well as their relative saline or 

 metallic contents, temperature, &c., have had a decided influence 

 on the deposition of minerals on them by electrical agency, so 

 that a given rock may have been electro-positive iia. one situation, 

 and electro-negative in another, in regard to other neighbouring 

 rocks, as this is quite consistent with voltaic phenomena. 



10. That the evolution of sulphuretted hydrogen, and the 

 tendency of some metals, when in solution, to absorb oxygen and 

 become insoluble, may in some instances have interfered with 

 the regular arrangement of the metals, such as electricity would 



