THEORIES OF ORE DISPOSITION HISTORICALLY CONSIDERED. 321 



Ihat this nu'lluxl of foniiatioii best fits the ore deposits of their 

 country. 



In Euijlaiul, tlie home of Phitonism, on the other hand, no very 

 decided views on theories of ore deposition were held. John Macciil- 

 lou^h. in lS'Jl-lS2o, after a discussion of the Wernerian-Huttonian 

 views, wisely concludes that it is necessary to study nature's proc- 

 esses more closely before a satisfactory theor}'- can be formulated. 

 He enumerates the minerals occurring in ore deposits which may be 

 foruKMl by infiltration or solution and by sublimation, contending 

 that many vein minerals can be produced in either way, and recom- 

 mends further investigations along that line. 



John Taylor, in his report on minelar veins to the British .Vssocia- 

 tion in 1833, makes a similar review and arrives at similarly indefi- 

 nite conclusions. 



Later, De la Beche, in his Geology of Cornwall (1839), says: 



The tlieories of the day divide tlieniselves into, first, the contemporaneous 

 formation of mineral veins witli tho rocks which inclose them; second, the 

 filling of fissures formed in rocks by the sublimation of substances driven by 

 lieat from beneath upward; and. third, the filling of fissures in rocks by chem- 

 ical deposits from substances in solution in the fissures, such deposits being 

 greatly due to electro-chemical agency. 



The contemporaneous theory, according to him, was still gener- 

 ally held among Cornish miners, but he himself is evidently more 

 inclined to the theoiy 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 popular- 

 ity among English geologists, was founded mainly on ohservations 

 made on the mine waters of Cornwall by Robert Ware Fox. This 

 theory assumed that vein minerals had been precipitated from solu- 

 tion 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 observations on the action of mine 

 waters on minerals were, moreover, rendered somewhat inconclusive 

 by the fact that he did not distinguish between primary vein min- 

 erals and those that have been formed during their secondary altera- 

 tion by surface waters. 



Among French geologists Plutonist views were predominant from 

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

 teaching, had for a time embraced his Neptunist theory soon re- 

 canted it when their field of observation had widened to include vol- 

 SM 1904 21 



