SALMON — MINERALOGICAL NOTES. 



65 



only where these rocks are subjected to a certain atmospheric decom- 

 posing action, by which the gold is dissolved, to be subsequently re- 

 precipitated in a highly concentrated state, that it is found in 

 appreciable quantities. This is strongly supported by the fact that 

 the finding of the gold-deposits is not limited to any arbitraiy depth, 

 but generally extends as far as the effects of atmospheric decompo- 

 sition, and no further. 



The question of the origin of gold deposits by the deposition of 

 the metal from solution is of course connected with the larger ques- 

 tion of the origin of most veins, either of the metallic or non-metalHc 

 minerals, in a similar manner. Omitting Bischoff, who may be con- 

 sidered by some a prejudiced authority, there are many first-rate 

 German mineralogists who hold the doctrine of such an origin for 

 most mineral veins. This scientific infiltration doctrine must not, 

 however, be confounded with a vague mining notion to the same 

 effect, and which would refer such views to a connection with the 

 present drainage of the country, and without any reference to an 

 origin of the metals ; an opinion which sometimes takes a form as 

 loose as that expressed by the Roman poet : — 



" Inque brevi spatio, quoo sunt effossa reponit 

 Tempns, inexhausti servans aJimenta metalli." 



No investigator on the subject of lithology has arrived at more 

 sweeping conclusions as to the origin of rocks than M. Delesse in his 

 "Etudes sur le Met amor phisme." Although M. Delesse's labours 

 have been completed for more than a year, it is to be regretted that 

 no complete abstract of them has been yet presented to English 

 readers.* That memoir is too wide a subject to enter upon here ; but 

 a short reference to another paper, by the same author, in vol. xv. of 

 the " Bulletin de la Society Geologique de France (p. 728), called 

 " Recherches sur I'origine des Roches," ia which he sums up the 

 conclusions of the investigations detailed in his " Etudes" may be in- 

 teresting to many. 



* M. Delesse's memoir has been often referred to, and was particularly ably 

 summed up by tlie President of tlie Geological Society in his last anniversary ad- 

 dress, which should be consulted by all who wish to read a comprehensive re- 

 view of the recent inquiries on this subject. 



VOL. III. I 



