172 M. Becquerel on the Electric Origin of 



It is true, Mr Fox, who has operated with plates of copper 

 and of zinc alternately, has observed in both cases currents 

 taking the same direction. Such^ result is so far favourable 

 to his opinion, but it is not sufficient to demonstrate completely 

 the fact. 



In order to shew in what manner electric currents have acted, 

 and are acting, on metalliferous deposits, some persons have re- 

 cently supposed that the veins have been filled by the action of 

 electric currents ; but it is only necessary to be acquainted 

 with the manner in which they are filled, to reject such a theory. 



We know that veins are fissures which occur in many of the 

 rocks composing the crust of our globe, and that they are filled 

 with metallic and stony substances. Different opinions are held 

 as to the manner in which this was effected. Some say by 

 igneous, others by aqueous action. Werner was of the latter 

 opinion. According to this celebrated geologist, the mass of 

 which mountains are composed was moist and yielding ; after- 

 wards, in settling and drying, fissures were formed, which were 

 filled from above by substances held in solution ; but, as there 

 are veins which appear to have been filled from beneath, we 

 must therefore admit that this was effected by sublimation. 

 Hutton, who is the great advocate of the igneous theory, sup- 

 posed the internal heat of the earth so great, as to melt and 

 volatilize the metals and earths. These, by their expansive 

 force, have produced rents in the crust of the earth, and solidi- 

 fying during their escape, have thus given birth to the crystal- 

 line rocks. It is thus he accounts for the production of the 

 great trap-dykes which traverse formations of all ages. 



Taking this view, veins have been opened by elevatory ac- 

 tion, and filled by sublimation from beneath, and from above 

 by substances which have been decomposed and transported by 

 various causes, and have rested undisturbed in the veins. 



All the facts hitherto observed induce us to think, that we 

 cannot admit one of these hypotheses to the exclusion of the 

 other, as each of the supposed causes may have concurred, ac- 

 cording to circumstances, in filling veins of various descriptions. 

 Geologists consider it certain, that veins containing the debris 

 of the superior (or newer) formations of the country they tra- 

 verse, and of organized bodies, have been filled from above ; 



