Ground Sluice.—All the sluices hitherto mentioned and described have wooden boxes, but the ground-sluice has no box: the water runs on the ground. The place selected for the ground-sluice is some spot where there is a considerable supply of water, a steep descent for it, and much poor dirt. The stream is turned through a little ditch, which the miners labor to deepen and enlarge, and when it is deep they prize off the high banks so that the dirt may fall down into the ditch. This is a very cheap and expeditious way of washing, but it is not applied extensively. It is used to the most advantage for washing where the water is abundant for only a few weeks after heavy rains, and where it would not pay to erect large sluices. A few cobble-stones should be left or thrown at intervals in the bed of the ground-sluice to arrest the gold, for if the bed were smooth clay, the precious metal might all be carried off. Quicksilver is not used in the ground-sluice. After the dirt has all been put through the ground-sluice, it is cleaned up in a short board-sluice, or a tom.
Long Tom.—The tom or long tom, an instrument extensively used in the Californian mines in 1851 and 1852, but now rarely seen, is a wooden trough about twelve feet long, eighteen inches wide at the upper end, and widening at the lower to thirty inches, with sides eight inches high. It is used like a board-sluice, but has no riffle-bars, and at the lower end its bottom is of sheet-iron, perforated with holes half an inch in diameter. This sheet-iron is turned up at the lower end, so that the water never runs over there, but always drops down through the perforated sheet-iron or riddle, into a little riffle-box, containing transverse riffle-bars. A stream of water of about ten inches makes a "tom-head"—or the amount considered necessary for a tom—through the tom, which has a grade similar to that of a board-sluice. The dirt is thrown in at the head of the tom, and a man is constantly employed in moving the dirt with a shovel, throwing back such pieces of clay as are not dissolved, to the head of the tom, and throwing out stones. From two to four men can work with a tom; but the amount of dirt that can be washed is not half that of a sluice. The tom may be used to advantage in diggings where the amount of pay-dirt is small and the gold coarse. The riffle-box contains quicksilver, and as the dirt in it is kept loose by the water falling down on it from the riddle above, a large part of the gold is caught; but where the particles are fine, much must be lost.
Cradle.—The rocker or cradle is still less than the tom and inferior in capacity. It bears some resemblance in shape and size to a child's cradle, and rests upon similar rockers. The cradle-box is about forty inches long, twenty wide, and four high, and it stands with the upper end about two feet higher than the lower end, which is open so that the tailings can run out. On the upper end of the cradle-box stands a hopper or riddle-box twenty inches square, with sides four inches high. The bottom of this riddle box is of sheet-iron, perforated with holes half an inch in diameter. The riddle-box is not nailed to the cradle-box, but can be lifted off without difficulty. Under the riddle is an "apron" of wood or cloth, fastened to the sides of the cradle-box and sloping down to the upper end of it. Across the bottom of the cradle-box are two riffle-bars about an inch square, one in the middle, the other at the end of the box. The dirt is shovelled into the hopper, the "cradler" sits down beside his machine, and while with one hand with a ladle he pours water from a pool at his side upon the dirt, with the other he rocks the cradle. With the water and the motion the dirt is dissolved, and carried down through the riddle, falling upon the apron which carries it to the head of the cradle-box, whence it runs downward and out, leaving its gold, black sand, and heavier particles of sand and gravel behind the riffle-bars. The man who rocks a cradle learns to appreciate the fact, that the "golden sands" of California are not pure sand, but are often extremely tough clay, a hopperful of which must be shaken about for ten minutes before it will dissolve under a constant pouring of water. Many large stones are found in the pay-dirt. Such as give an unpleasant shock to the cradle, as they roll from side to side of the riddle-box, are pitched out by hand, and after a glance to see that no gold sticks to their sides, are thrown away; but the smaller ones are left until the hopperful has been washed, so that nothing but clean stones remain in the riddle, and then the cradler rises from his seat, lifts up his hopper, and with a jerk throws all the stones out. The water and the rocking are both necessary. Without the water, the dirt could not be washed; and without the rocking, the dirt would dissolve very slowly, and the gold would most of it be lost. The rocking keeps the dirt in the bottom of the cradle more or less loose, so that the particles of gold can sink down in it, whereas if the cradle stood still, the sand there would almost immediately pack down into a hard floor, over which the gold would run almost as readily as over a board. The whole business of washing with a cradle, is a repetition of the process already described—some dirt, about one-third or one-fourth of what the hopper would hold, if full, is put into the hopper, and while the cradle is rocked with one hand, the other pours in the water. The cradle is cleaned up two or four times in a day. The cleaning up is done by lifting the hopper, taking out the apron, scraping up all the dirt in the bottom of the cradle with an iron spoon, putting it into a pan and washing out the dirt, so that only the gold will be left. This last process is called panning out, and will be described in the next section. Most of the gold collects above the upper riffle-bar, including all the larger lumps. If the apron be of rough woollen cloth, some of the fine gold will be caught there. In diggings where the gold is very fine, the hopper is sometimes placed over the lower end of the cradle, and the apron is made twice as long, and with a lower inclination than in the more common form of the rocker. The water for the cradle should be supplied by a little ditch, with a reservoir at the head of the cradle, to contain five or six gallons. The dipper should be of tin, shaped like a basin, hold about a gallon when full, and have a handle an inch and a half in diameter, and eight inches long. The difference of height between the upper and lower ends of the cradle should not be more than two inches: a steeper inclination will make the current running through it too strong, and the gold will be carried off; and, on the other hand, if the cradle be nearer a level it will be hard to rock, and the dirt in the bottom will pack more rapidly. The amount of dirt that can be washed in a day with a cradle, varies from one to three cubic yards. The dirt is usually shovelled into a pan or bucket, from which it is thrown into the hopper. The miners usually measure the amount of dirt washed by the number of "pans." One man working alone with a cradle ought to wash from seventy-five to one hundred and fifty pans in a day, and two men will wash twice as much. A pan may contain one-third or one-half of a cubic foot. Two men can work more conveniently with the rocker than one. There is enough work to give constant employment to a cradler and a shoveller. The latter has a couple of buckets or pans, which he fills alternately, always keeping one full and near the cradler, so that without moving his feet he can pick it up and empty it into the riddle-box. If the rocker have only one man, he must stop rocking after washing every pan and get more dirt. This delay is injurious to the process of washing, because it allows the dirt in the bottom of the cradle to harden and pack, and some gold is always lost as a consequence. If the dirt and water be convenient, not more than two men can work to a profit with a rocker. But sometimes it happens that water cannot be led to the claim, and in such case the dirt must be carried to the water, a greater weight of which is used than of dirt. At least three times as much water as dirt is required for washing. If the distance from the hole to the water be not over ten or twenty feet, the miners will usually carry the dirt in buckets; if farther they will use wheelbarrows; and sometimes for greater distances pack-mules or waggons. The greater the distance, the more the men required for carrying the dirt. Sometimes, too, it happens that the claim is troubled by water, and then one man may be constantly employed in bailing.
It is of great importance in mining with the cradle, to have the cradle placed within four or five feet of the hole from which the pay-dirt is obtained, and to have a good supply of water at the head of the cradle, and then to have a good descent below the cradle, so that the tailings may all be carried away by the water, so as not to accumulate. The rocker washes about one-half the amount of dirt that can be washed by an equal number of men with the tom, one-fourth of what can be washed with the sluice, and one-hundredth of the amount that can be washed with the hydraulic process; but it is peculiarly fitted for some kinds of diggings. Many little gullies, containing coarse gold in their beds, cannot obtain water for washing except during rains, and then only for a few days at a time. In these gullies the cradle can be used to the best advantage, for it can easily be transported, and it is very good for saving coarse gold. While dirt that would pay from ten to twenty-five cents, was abundant at the surface of the earth in the Californian mines, the cradle was extensively used, but now it has been abandoned by the whites, and is left to the Chinamen, who think themselves doing well if they make seventy-five cents or one dollar per day.
The great difficulty in mining with the cradle is, that the sand will "pack," or make a hard mass on a level with the top of the riffle-bars, and the gold then is lost. So long as the cradle is in motion the dirt does not pack, but when the rocking ceases, the mass hardens in a few minutes. If the miner leaves his cradle standing for fifteen minutes, he stirs up the dirt with his spoon before commencing again to wash. One device to prevent packing is to put a little block under each end of the rockers, so that at the end of every motion the cradle receives a shock. Quicksilver is sometimes used in cradles, but not usually.
Pan.—The pan is used in all branches of gold mining, either as an instrument for washing, or as a receptacle for gold, amalgam, or rich dirt. It is made of stiff tin or sheet-iron, with a flat bottom about a foot across, and with sides six inches high, rising at an angle of forty-five degrees. A little variation in the size or shape of the pan will not injure its value for washing. Sheet-iron is preferable to tin, because it is usually stronger and does not amalgamate with mercury. The pan is the simplest of all instruments used for washing auriferous dirt. Some dirt, not enough to fill it full, is put in, and the pan is then put under water. The water ought to be not more than a foot deep, so that the pan may rest on the bottom, while the miner inserts his fingers in and under the dirt and lifts it up a little, so that the whole mass is wet. If the water be deep, the pan may be held in one hand while the other is used to stir up the dirt, but it is more convenient to take both. The dirt having been filled with water, the miner catches the pan at the sides, raises that part toward his body, and lowers the outer edge a little, and commences to shake the pan from side to side, holding it so that all the dirt is under water, and so that a little of the dirt can escape over the outer edge. The earthy part of the dirt is rapidly dissolved by the water, assisted by the shaking of the pan and the rolling of the gravel from side to side, and forms a mud which runs out while clean water runs in. The light sand flows out with the thin mud, while the lumps of tough clay and the large stones remain. The stones collect on the top of the clay, and they are scraped together with the fingers and thrown out. This process continues, the pan being gradually raised in the water, and its outer edge depressed, until all the earthy matter has been dissolved, and that as well as the stones swept away by the water, while the gold remains at the bottom. Panning is not difficult, but it requires practice to learn the degree of shaking, which dissolves the dirt and throws out the stones most rapidly without losing the gold. If the shaking be too mild and slow, the process consumes too much time; whereas if it be too rapid and violent, the gold is carried off with the stones. Sometimes the pan is shaken so that the dirt receives a rotary motion. This is the most rapid method of washing dirt, but also the most dangerous. The pan must always be used in cleaning up the dirt which collects in the cradle, in prospecting, and frequently in washing small quantities of dirt collected in other kinds of placer mining. Amalgam can be separated from dirt by washing, almost as well as gold. In panning out, it frequently happens that considerable amounts of black sand containing fine particles of gold are obtained, and this sand is so heavy that it cannot be separated from the gold by washing, while it is easily separated by that process from gravel, stones and common dirt. The black sand is dried, and a small quantity of it is placed in a "blower," a shallow tin dish open at one end. The miner then holding the pan with the open end from him, blows out the sand, leaving the particles of gold. He must blow gently, just strong enough to blow out the sand, and no stronger. From time to time he must shake the blower so as to change the position of the particles, and bring all the sand in the range of his breath. The gold cannot be cleaned perfectly in this manner, but the sand contains iron, and the little of it remaining is easily removed by a magnet. The blower should be very smooth, and made of either tin, brass or copper.