16 = Joseph LeConte—Genesis of Metalliferous Veins. 
plish the same result. For example, if a double sulphate of 
iron and gold may exist in the presence of alkaline bicarbonate 
and alkaline sulphide (which, however, seems more than doubt- 
ful), then we may well imagine that organic matters in solution 
would reduce these to sulphides, the gold returning to the me- 
tallic condition as before. Or acids of organic decomposition 
might neutralize the alkali and force it to deposit the metallic 
sulphides in solution, the gold as before returning to the metallic 
condition. 
I have assumed that the gold is in a native state. This is by 
no means certain in all cases. Gold exists as telluride, and may 
exist as sulphide along with other sulphides. In that case the 
difficulty of explaining the deposit would be much less. 
ese views are, elieve, substantially sustained by the 
observations of Arthur Phillipson the re-solution and re-deposit 
of gold probably still going on in the deep placer gravels of 
California. These gravels have been, and still are, traversed by 
alkaline waters, certainly alkaline carbonate, and probably also 
alkaline sulphide. .The waters were certainly at one time, if 
not now, hot; for the gravels are deeply covered with lava. 
These alkaline waters dissolve out the silica from the slate bed- 
rock and the slate and volcanic pebbles, leaving these as tough, 
soapy blue clay (putty stones), and re-deposit the silica in their 
course, cementing the gravels and petrifying the drift-wood.* 
On the partially petrified drift-wood, in some places the silica is. 
still found in a gelatinous condition, showing that the process 
is still going on. That the same waters carried iron in solution 
is proved by the abundant deposit of iron sulphide on the drift- 
wood. That they also in some cases carried gold is shown by 
the fact that in a few cases the iron sulphide thus deposited, 
when dissolved in nitrie acid, leaves gold in crystals, threads 
and scales, like those found in true auriferous veins.+ 
Such are the phenomena. Now the explanation. Since in 
this case the water is now at ordinary temperature and moving 
nearly horizontally, and therefore not losing heat and pressure, 
the simplest explanation seems to be as follows: alkaline car- 
bonate and alkaline sulphide waters, circulating through the 
gravels, dissolved and redeposited the silica, cementing the 
gravels and petrifying the drift wood. They dissolved also 
both iron and drift gold found in their course, and carried 
them in solution as sulphides of iron and gold. Coming in 
contact with decaying drift-wood, the alkali was umaccibet by 
the acids of organic decomposition, the silica and the two me- 
tallic sulphides were all deposited, the gold giving up its 
sulphur at the moment of its deposition. Or if it be possible 
* Old River Beds of California, this Journal, vol. xix, p. 176, 1880. 
+ Arthur Phillips, Phil. Magazine, vol. xliii, p. 401, 1872. 
