President of the Geological Society for 1850. 33 



de Beaumont, that a large class of metalliferous veins may 

 simply be regarded as extinct mineral springs. They are 

 fissures in which vapours, or thermal waters charged with 

 various elementary bodies, have precipitated the materials of 

 a refractory kind, or those which are the least easily retained 

 in solution. The marked agreement between the contents of 

 mineral springs and the emanations from active volcanoes 

 strongly supports this view. But why should we doubt that 

 fissures now existing in solid rocks may in like manner com- 

 municate at one extremity with subterranean masses of fused 

 matter, while at their upper end they terminate in mineral 

 springs ? and if so, why may not hot steam and gases and 

 mineral waters be depositing at this moment, as actively as 

 ever, that class of elementary bodies, whether metalliferous 

 or not, which we find in the oldest veins \ The steam or hot 

 water will always part with these substances in the deeper 

 parts of every fissure, and merely bring up to the surface the 

 residuary salts which are more soluble and volatile. Hence 

 mineral veins are marked by the habitual absence of alkalies, 

 which are so readily dissolved in water. 



When we consider the grand and reiterated movements of 

 elevation and depression which have agitated the earth's 

 crust since the palaeozoic epoch, and the vast amount of vol- 

 canic action which can be shown to have been of subsequent 

 date, it is evident that all those refractory bodies said to 

 have been " withdrawn from circulation," must have been 

 from time to time re-melted, and therefore re-issued from 

 the grand subterranean mint. Their circulation may always 

 be confined to the interior of the earth, and they may never, 

 except in very minute quantities, be disengaged superficially. 

 If it be so, they must always be ancient in all future systems 

 of geological classification ; not because they originated at 

 remote eras, but because time is required to uplift and expose 

 them to view. 



No illusion, indeed, is more likely to mislead us in our 

 chronological speculations than the temptation to ascribe to 

 antiquity appearances which are in reality characteristic of 

 a deep subterranean or submarine origin. Volcanic rocks 

 now forming at a certain distance below the surface, or sedi- 



VOL. L. NO. XCIX.— JANUARY 1851. C 



