250 RESOURCES OF CALIFORN^IA. 



slnice runs only during daylight, but in some claims the work 

 continues night and day. Cleaning up occupies from half a 

 day to a day, and therefore must not be repeated too often, 

 because it consumes too much time. In some sluices the clean- 

 ing up does not occur until the riffle-bars have been worn out 

 or much bruised by the wear of the stones and gravel. Clean- 

 ing up is considered light and pleasant work as compared with 

 other sluicing, and is often reserved for Smiday. At the time 

 fixed, the throwing in of dirt ceases, and the water runs until 

 it becomes clear. Five or six sets of riffle-bars, a distance of 

 thirty or thirty-five feet, are taken up at the head of the sluice, 

 and the dirt between the bars is washed down, while the gold, 

 and amalgam lodge above the first remaining set of riffle-bars, 

 whence it is taken out with a scoop or large spoon, and put 

 into a pan. Five or six more sets of bars are taken up, and 

 so on down. Sometimes all the riffle-bars are taken up at 

 once, save one set in every thirty-six feet, and then the work 

 of cleaning up is dispatched much more rapidly. 



The quicksilver and amalgam taken from the sluice are put 

 into a buckskin or cloth, and pressed, so that the liquid metal 

 passes through, and the amalgam is retained. The amalgam 

 is then heated, to drive off the mercury. This may be done 

 either in an open pan or in a close retort. In the former, the 

 quicksilver is lost ; in the latter, it is saved. The pan is gen- 

 erally preferred. Often a shovel or plate of iron is used. 

 Three pounds of amalgam, from which the liquid metal has 

 been carefully pressed out, will yield one pound of gold. The 

 gold remaining after the quicksilver has been driven off by 

 heat from the amalgam, is a porous mass, somewhat resem- 

 bling sponge-cake in appearance. 



§ 182. Riffle- Bars. — The riffle-bars are usually sawn longi- 

 tudinally with the grain of the wood, but "block riffle-bars" 

 are considered preferable ; the latter are cut across the tree, 

 and the grain stands upright in the sluice-box. The block 

 riffle-bars are three times moi'e durable than the longitudinal ; 

 and as the latter kind are worn out in a week in some large 



