; 51<» The American Geologist. May, 189© 
And first, what is the origin of these mineral waters? 
The frequent association of metalliferous deposits and 
eruptive rocks, the presence in the latter of metals in the con- 
dition of minute grains or inclusions and the observation of 
volcanic phenomena have served as a basis for the theory of 
fumeroles, which although ingenious is none the less debata- 
able. The quantity of metals found in eruptive rocks is so 
small that it appears absolutely inadequate to account for 
metalliferous deposits. 
Would this separation of metals that appears so extraordi- 
nary for entire and enormous massifs of surface rocks take 
place at great depths? In that case what would become of 
the fumeroles? The metalliferous deposits would need to be 
formed before the consolidation of the eruptive rocks. But 
we find the contrary to be true. The real advent of the met- 
als is always of later date and affects relatively limited sur- 
faces of the rocks. The phenomena of to-day seem to us in- 
capable of explaining the origin of extensive metalliferous 
regions. 
M. Parran in an unpublished work* expresses himself as 
follows : 
"It should be remarked, however, that metalliferous inclu- 
sions disseminated through the rocks do not explain the exis- 
tence of the associated massive and sometimes colossal deposits 
of compounds of sulphur and iron or copper (Huelva, Tuscany, 
Chessy, lake Superior [?] etc.) It is necessary to assume 
either the mechanical introduction of copper matte along w T ith 
the associated lava or solfataric action which always accompa- 
nies eruptive phenomena, or perhaps the two causes together." 
We believe that mineral waters may be perfectly independ- 
ent of eruptive rocks in the strict sense of the term. Metal- 
liferous solutions (emanations) are derived from the molten 
hath which supports the lava or magma whence all eruptive 
rocks arise. When vapors carrying metals have reached the 
solid crust of the earth and find themselves, at a certain point 
in their ascending course, in the presence of water, the reac- 
tions caused by surface waters may produce conditions of 
which we know absolutely nothing. 
♦Evolution metamorphique des roches basiques et leur contribution & 
la formation des depots filoniens et sedimentables. Oct. 15, 1888. 
