Joseph LeConte—Genesis of Metalliferous Veins. 17 
(which I think it is not), that iron and gold should exist as sul- 
phates in the presence of alkaline bicarbonates and bisulphides, 
we may suppose these were reduced to sulphides by organic 
decomposition and the gold set free as before. In the dee 
gravels with the lava cap above, the slate bed rock beneath and 
solfataric waters flowing between and depositing silica and 
metallic sulphides in their course, we have exactly the phenom- 
ena of metalliferous-vein-formation, except that in this case 
the water-way is horizontal. It is in fact a horizontal vein. 
8. Different kinds of veins.—If we assume then as probable the 
main principles sustained in the preceding pages, it is not diffi- 
cult to account for all the different kinds of veins described 
a. 
their courses, i. e., in water-ways; but these subterranean wa- 
ec 
¢. Brecciated veins—Or sometimes by repeated back and forth 
Am. Jour, aged Series, VoL. XXVI, No. 151.—Jury, 1888. 
