We have already described panning, the crudest manner of separating gold from gravel. The appliances which Uncle Will and his helpers had now constructed were capable of doing much more work than the pan in a given time, yet required the expenditure of comparatively little labor. Uncle Will first called Roly's attention to the rocker, which at that moment was standing idle at the side of the stream. "The rocker, or cradle," he explained, "consists of a deep box set upon rounded rockers so that it can be swayed from side to side. Within the box are several inclined planes at different heights, covered with canvas and so arranged that water and gravel flowing down the upper one will pass from its lower edge through an aperture to the top of the one below, and from that to the next, until finally the stream issues near the bottom of the machine. Across these planes at intervals are nailed small strips of wood called riffles. A sieve is fitted to the top of the box, its bottom being made of a sheet of tin punched with numerous holes half an inch in diameter. Now let us see it work." So saying, he placed the rocker under the end of a wooden trough set in the bank at a height of three feet. A ditch had been hollowed along the bank to this trough from a point higher up the stream, and David now lowered a similar trough into the water at the upper end. This allowed a stream to come into the ditch from the creek. As soon as the water began to pour into the sieve of the rocker, Coffee Jack, whom Uncle Will had summoned, threw into it a shovelful of gravel from the bottom of the bank. "Now you see," said Uncle Will, as he gently rocked the machine from side to side, "the water carries the sand and smaller pebbles, including the particles of gold, down through those holes and over the riffles on the inclined planes. The gold is so heavy that it lodges against the riffles, but the water, swashing from side to side as it flows down, carries most of the sand and gravel over the riffles and out at the bottom. The operation is almost instantaneous in the rocker, and gravel can be shovelled in quite rapidly, whereas it would take perhaps ten minutes to wash out a very little in a pan. When the sieve becomes choked, it is lifted up and the stones thrown out." Coffee Jack shovelled mechanically, as if all this fuss about the yellow metal were quite beyond his appreciation. In a few minutes Uncle Will released him and sent him back to help Lucky at the sluice. "Now we'll take a look at the results," said Uncle Will, as he removed the sieve, picked out the riffles, which were loosely nailed, and carefully took up the canvas which covered the inclined planes. All the sand and gravel which remained upon the canvas he rinsed off into a pan and proceeded to wash it out at the stream after the usual method of panning. Roly was delighted to see two little yellow nuggets appear, besides many small flakes and grains.