SALMON — MINKKALOUICAL NOTES. 65 
only where these rocks are subjected to a certain atmospheric decom- 
posing action, by which the gold is dissolved, to bo subsequently rc- 
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 arbitrary depth, 
but generally extends as far as the effects of atmospheric decompo- 
sition, and no fiu'ther. 
The question of the origin of gold deposits by the deposition of 
the metal from solution is of coui'se connected with the larger ques- 
tion of the origiu of most veins, either of the metalHc or non-metallic 
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, qnae sunt effossa reponit 
Tempus, inexhausti servana alimenta metaUi." 
No investigator on the subject of Hthology has arrived at more 
sweeping conclusions as to the origin of rocks than M. Delesse in his 
"Etudes sur le Metamorphisme." 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 Societe Geologique de France (p. 728), called 
" Recherches sur I'origine des Roches," in which he sums up the 
conclusions of the investigations detailed in his " Etudes" may be in- 
teresting to many. 
* M. Delesse's memoir lias been often referred to, and was particularly ably- 
summed up by the President of the 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 
