14 S. F. EMMONS — THEORIES OF ORE DEPOSITION 



to the theory of deposition by solutions ascending under the influence 

 of internal heat, the water being furnished from the sea, which covered 

 many of the Cornish lodes. 



The electro-chemical theory, which had already been suggested in 

 1810 by Bergrath Schmidt, and for a time enjoyed a certain popularity 

 among English geologists, was founded mainly on observations made 

 on the mine waters of Cornwall by Robert Ware Fox. This theor}' 

 assumed that vein minerals had been precipitated from solution under the 

 influence of electrical currents. It would appear, however, that, owing 

 to the imperfect knowledge of chemistry of that time, the believers in 

 this theory assumed electric currents to be a necessity for the production 

 of certain reactions when they only serve to facilitate them. Fox's ob- 

 servations on the action of mine waters on minerals were, moreover, 

 rendered somewhat inconclusive by the fact that he did not distinguish 

 between primary vein minerals and those that have been formed during 

 their secondary alteration by surface waters. 



Among French geologists, Plutonist views were predominant from the 

 first; even those who under the influence of Werner's magnetic teach- 

 ing had for a time embraced his Neptunist theory soon recanted it, 

 when their field of observation had widened to include volcanic regions. 

 The cosmic theory, general^ known as the " nebular hypothesis," the 

 one which has been most universally accepted by geologists as an ex- 

 planation of the earth's beginnings, as finally received, was the work of 

 a French mathematician, Laplace (1796). Hence, in seeking to account 

 for the origin of ore deposits they were naturally inclined to look for 

 igneous agencies. Thus, A. Burat, well known through his work, "Ap- 

 plied Geology " (1843), took extreme Plutonic views and divided the 

 copper, lead, and iron deposits of the Italian peninsula, which he had 

 especially studied, into (1) dikes or eruptive masses, with gangue of 

 amphibolite and ilvaite, and (2) irregular veins of contact between erup- 

 tive serpentine and sedimentary rocks. The Elba deposits of specular 

 iron, which he regarded as striking instances of the first class, he con- 

 sidered to have exercised an elevatory as well as metamorphic action on 

 the enclosing rocks at the time of their injection. Fournet, another 

 prominent authority on the subject, maintained a theory of igneous 

 injection for vein fillings as late as 1859. 



As in Germany it was the professors in the mining schools, especially 

 those at Freiberg, who in the early part of the century led in forming 

 scientific opinion as to ore deposition, so it was the School of Mines at 

 Paris which later furnished the leaders in that branch of geological 

 thought. 



The French students of underground phenomena were at a certain dis- 



