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September 25, 1862: Douglas City

September 25, 2012

[This morning], September 25, we started for the place, Douglas City, on the Trinity River, six miles south. We found no fossils there, but very extensive “hydraulic” diggings.

The river here makes a curve. A stratum of soil twenty or thirty feet thick forms a flat at the curve of the river, of limited extent. The “bed rock” beneath this is of metamorphic slates, much twisted, contorted in every shape by former volcanic convulsions, and much of it very hard. The soil above is very hard, like rock itself, made up of loose rounded bowlders, cemented by a firm red clay into a mass as hard as ordinary sandstone. In this the gold is found.

Deep ditches are cut, not only through this, but deep down into the hard bed rock beneath, often twenty or more feet into the latter, and running out to the river. In these are the “sluices”—merely long troughs for conveying the water. The bottoms of these sluices are made of blocks sawed from the ends of partially squared timber, so that the end of the grain is presented to the surface, sometimes of a double row, thus—

sometimes, however, of but a single row of blocks. These do not lie perfectly square and level, so, as the water flows swiftly over them, they cause a ripple, like water flowing swiftly over the stony bed of a stream. The bottom of the box or trough, below these blocks, is perfectly tight, and quicksilver is poured in and collects in all the holes between the blocks.

Ditches, from miles back in the mountains, bring the water up against the hillside, far above the surface of the flat, and a flume, or “raceway,” built on high stilts, over seventy or one hundred feet high, brings the water directly over the “claim.” A very stout hose, often six inches in diameter, conducts the water down from this high head, and has at its end a nozzle like that of a fire engine, only larger. Now, this stream of water, heavy and issuing with enormous force from the great pressure of so high a head of water, is made to play against this bank of hard earth, which melts away before it like sand, and all flows into the sluices—mud, bowlders, gold. The mud is carried off in the stream of thick, muddy water; the bowlders, if not too large, roll down with the swift current; the heavier gold falls in the crevices and is dissolved in the quicksilver, as sugar or salt would be in water. In some mines these sluices are miles long, and are charged with quicksilver by the thousands of pounds. This washing down banks by such a stream of water under pressure is “hydraulic mining.” After a certain time the sluices are “cleaned up,” that is, the blocks are removed, the quicksilver, amalgamated with the gold, is taken out, the former being then driven off by heat—“retorted”—and the gold left.

From this flat near Douglas City over a million dollars has already been taken, and it looks as if as much more was yet to be got. Owing to the want of water at present the sluices were dry, and men were only preparing for water when the rains should commence.

The amount of soil removed in hydraulic mining must be seen to be at all appreciated. Single claims will estimate it by the millions of tons, the “tailings” (refuse from the sluices) fill valleys, while the mud not only muddies the Sacramento River for more than four hundred miles of its course, but is slowly and surely filling up the Bay of San Francisco. In the Sierra, the soil from hundreds of acres together has already been sluiced off from the rock, which it formerly covered even to the depth of 150 feet! I have seen none of the heavy mining as yet, although I have seen works and effects that one would imagine it would take centuries to produce, instead of the dozen years that have elapsed since the work began.

Well, this we found, but we found no fossils, and no formation at all possible to contain them.

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