IX PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



we not adopt as tlie most probable conjectiu'e tlie idea that this mat- 

 ter is now, as of old, passing into gi'anite, or iato some of the grani- 

 tiform compomids, more especiallv wlien we know tliat silex abounds 

 in many modern lavas, and tliat certain obsidians and pumice do not 

 differ materially in their component elements from granite. 



I fully assent to the doctrine so ably advocated by ]\I. E. de 

 Beaumont, that a large class of metalliferous veins may simply be 

 regarded as extinct mineral spiings. They are fissures in which va- 

 pours, or thermal waters charged with various elementary bodies, 

 have precipitated the materials of a refractory kind, or those which 

 are the least easily retained hi solution. The marked agreement be- 

 tween the contents of mineral springs and the emanations from active 

 volcanos strongly supports this view. But why should we doubt that 

 fissui'es now existing ui sohd rocks may in hke manner communicate 

 at one extremity with subterranean masses of fnsed matter, wlhle 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 hi the oldest veins ? The 

 steam or hot water will always part with these substances hi 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 alkahes, which are so 

 readily dissolved hi water. 



"^iVhen we consider the gi'and and reiterated movements of eleva- 

 tion and depression which have agitated the earth's crust since the 

 paleeozoic epoch,, and the vast amount of volcanic action which can 

 be shown to have been of subsequent date, it is evident that all those 

 refractoiy bodies, said to have been *• withdrawn from chculation," 

 must have been from time to time re-melted, and therefore re-issued 

 from the grand subterranean mint. Then- circulation may always be 

 confined to the ulterior of the earth, and they may never, except in 

 yeiy minute quantities, be disengaged superficially. If it be so, they 

 must always be ancient in all fnture systems of geological classifica- 

 rion ; not because they originated at remote seras, but because rime 

 is required to uplift and expose them to view. 



No illusion indeed is more likely to mislead us in our chronologi- 

 cal specularions than the temptarion to ascribe to antiquity appear- 



