River-Mining.—River-mining is mining for gold in the beds of rivers, below low-water mark. The only practicable method of doing this is by damming the stream, and taking the water out of its bed, in a ditch or flume. It has been proposed by persons who never saw the mines, to get the gold by dredging, or with a diving-bell; but such schemes are absurd in the eyes of miners. The rivers in which the gold is found are mountain-torrents, in which a canoe can scarcely float in summer, much less a dredging machine; and any large scoop working under water would miss the crevices and corners in the rocks, where most of the gold is found. As the water is very seldom more than a couple of feet deep, a diving-bell would be of little service. The flume, the ditch, and the wing-dam, are the chief tasks of the river-miner. The ditch is rarely used, because the banks of the mining-streams are usually so steep, high, rocky and crooked, that a flume is cheaper. The wing-dam is not often used, because the river-beds are in most places too narrow. The flume is almost universally employed.

The work of river-mining can be done only during the summer and fall, while the water is low, and while the miner can have confidence that it will not rise. It may be as low in January as in August, but the winter is the season of rains; and when the flood comes, it sweeps dams, flumes and every thing before it. If the dam and flume be commenced too early in the season, they may be carried off before they are finished; and it frequently happens that they are destroyed in the fall just when the miners are commencing to reap the reward of their summer's labor.

River-mining has many disadvantages, as compared with other branches of mining. The miner cannot work at it more than half the year; he cannot prospect the dirt which is hidden under water; he must erect expensive dams and flumes, which can be used for only a few months; and then he is exposed to floods which may come and destroy all his work before he has commenced to wash. These disadvantages, and the exhaustion of most of the river-diggings in the state, have almost put an end to river-mining in California. In a few cases, extensive fluming enterprises have proved profitable; but, as a general rule, river-mining in this state has cost more than it has produced. A river is seldom flumed for less than three hundred yards, and sometimes for a mile; and the lumber and labor required to make so long a flume, and one large enough to hold all the water of a river, are very expensive. The dam will always leak, and water will run into the bed from the adjacent hills and mountains, and this water must be lifted out by pumps driven by wheels placed in the flume. The river-beds are full of large rocks, weighing from one to ten tons, and these must be moved by machinery, to allow the dirt to be taken out.

River-mining is now never undertaken by an individual, but always by large associations, generally called "fluming companies," sometimes composed of miners exclusively, sometimes of miners and all the principal business-men living near the place where the work is to be done. The lawyers, doctors and office-holders, pay their assessments in cash; the merchants furnish provisions, the lumbermen supply lumber, and the miners make the dam, and help the carpenters build the flume.

Beach-Mining.—Beach-mining is the business of washing the sands of the ocean-beach. Between Point Mendocino, in California, and the mouth of the Umpqua River, in Oregon, the beach-sand contains gold, and in some places it is very rich. The beach is narrow, and lies at the foot of a bluff bank of auriferous sand. In times of storm, the waves wash against this bank, undermine it, sweep away the pieces which tumble down, leaving the gold on the beach. The gold is in very fine particles, and it moves with the heavier sand, which alters its position frequently under the influence of the waves and surf. One day, the beach will have six feet depth of sand; the next, there will be nothing save bare rocks. The sand differs greatly in richness at various times: one day, it will be full of golden specks; a few days later, at the same place it will be barren. The sand in the mean time has been moved by the waves, and replaced by other sand.

It is a very difficult matter to know where the sand is rich and where it is not. The companies employed in mining on the beach number about ten men; and there is a foreman who rides out early every morning, following the beach about two miles to the northward and two miles to the southward of the camp, for the purpose of finding where the sand is the best. So changeable is the sand, that a new examination is made every day; and only three or four men are supposed to be good judges of the quality of sand, from its appearance.

When the foreman has selected a place, he orders all the men to it, and they go with twenty pack-mules, which carry the sand in alforjas, or raw hide sacks, to the place of washing, which is up on the bluff, probably a mile or more distant from the spot where the sand is obtained. It happens occasionally that the foreman rides long distances on the beach, and sometimes he will order the sand to be obtained ten miles from the washing-place. The sand must, of course, be very rich, to pay for such transportation, but the beach-sand at times in the sunlight is said to be actually dazzling yellow with gold. The purpose of going upon the bluff to wash it, is to get fresh water for washing; for the sea-water is not so good, nor can it be obtained conveniently. The richest dirt is that the farthest down on the beach, so still weather and low tide are the best times for getting it. When a rich place is discovered low down on the beach, great exertions are made to get as much of the sand as possible before the tide rises. When high tide and storm come together, little can be done. The sand, having been separated from all clay and soluble matter by the action of the sea, is very easily washed, and all collected in a month can be washed in two days in a sluice.

Mining-Ditches.—The placer-mines of California would yield very little gold, were it not for the numerous ditches which supply them with water for washing. The auriferous districts are very dry in summer, and in some places there is not a spring nor a brook within many miles. The artificial ditch supplies the want. The ditches are made by large companies, which sell the water by the "inch." An inch of water is as much as will run out of an orifice an inch square, with the water standing six or seven inches deep in the flume over the orifice. The depth of water over the orifice is called the "head." The orifice is usually two inches high, and as long as necessary to give the amount of water desired. Nobody wants less than ten or twelve inches for mining: a "sluice-head" is about eighteen inches; a "hydraulic-head" is from forty to two hundred inches. The water, however, is not measured accurately. Of course the amount which runs through the orifice will depend to a considerable extent upon the "head," which is usually greater in the morning than at night. At sunrise there may be fifteen inches head, and at sunset only three. The water collects during the night, and is exhausted during the day. The price of water is in no place less than ten cents an inch per day; in some places it is forty cents; the average is about twenty cents.

Many of these ditches are extensive enterprises, and have cost hundreds of thousands of dollars. When they cross ravines and valleys, large flumes—wonders of carpentry—must be built. Some of these are two hundred feet high and a mile long, and so large that a horse and waggon can be driven through them. In all, save length and durability, they are as wonderful as the great Roman aqueducts, whose tall ruins still stand in the Campagna, near the Eternal City. In some cases iron tubes have been used, and although they are very expensive, yet they may pay for themselves, by