ASCENSION OR LATERAL SECRETION. 569 



from the free carbonic acid and organic acids which they take up at the 

 surface, it seems probable that these would have been neutralized and the 

 solvent power largely lost long- before they could have reached depths 

 comparable with those at which these deposits were formed. 



ORIGIN OR SOURCE OF THE METALLIC MINERALS. 



Ascension or lateral secretion. The origin of the metallic contents of ore de- 

 posits has been, from the very earliest days of geology, a most fruitful theme 

 of speculation and theorizing, probably for the very reason that so little has 

 been done toward obtaining data, founded upon actual observations or 

 experiments, to support one theory or exclude another. In the days of the 

 bitter contests between Neptunists and Plutonists the supporters of either 

 school allowed only the extreme alternatives, that the vein materials were 

 washed into the veins from the surface (descension theory) or that they 

 were forced into them in a molten condition from below (ascension theory). 

 Probably in either case, in the heat of the contest, they went beyond the 

 real opinion of the originators of the school, for it does not appear from the 

 writings of "Werner, 1 the father of the Neptunist school, that he himself 

 went further than to maintain that veins were filled by deposit from solu- 

 tions reaching them from above, without attempting to indicate the source 

 from which these solutions derived their metallic contents. The idea of the 

 original ascensionists, or more properly, injectionists, that the mineral con- 

 tents of ore deposits could have been injected into their present position in 

 a fused state, is so opposed to all observed facts that it has long since been 

 abandoned ; and probably no one would maintain that original ore deposits 

 are derived from waters at present flowing on the surface. 



There still remains a tendency among writers to separate themselves 

 into upholders of modifications of one or the other of these original theories, 

 but an impartial examination of their views shows that, so far as their foun- 

 dation in well-ascertained facts or on legitimate deductions from these facts 

 goes, there is really no great essential difference between them. Thus the 

 French geologists, who, by the prominence given to the synthetic experi- 

 ments of Se"narmont, Daubre"e, and others, may be considered to be the 



1 A. G. Werner, Nene Theorie der Entstehnng der Giinge. 1791. 



