Under the continuous action of this enormous force, aided by the softening power of the water, large sections of the gravelly mass are dislodged, and fall with great violence, the debris speedily disintegrating and disappearing under the resistless force of the water, and is hurried forward in the sluices to the mouth of the shaft, down which it is precipitated with the whole volume of turbid water.  Bowlders of 100 to 200 lb. in weight are dislodged and shot forward by the impetuous stream, accompanied by masses of the harder cement which meet in the fall, and by the concussion from the great bowlders the crushing and pulverizing agency required is found to disintegrate it.  The heavy banks, of 80 feet and upward, are usually worked in two benches, the upper never being so rich as the lower, and also less firm, and therefore worked away with greater rapidity.

The lower section is much the more compact, as this stratum on the bed rock being strongly cemented resists great pressure, and even sometimes the full force of the streams of water, until it has been loosened by gunpowder or other explosives.  For this purpose adits are driven in on its foundation-point of from 40 to 70 feet and more from the face of the bank, and drifts are extended at right angles therefrom to a short distance on each side of the adit, and in these drifts a large quantity of gunpowder is placed (from 1 to 3 tons), and fired at one blast, having been previously built in with masonry.  And in this manner the compact conglomerate is broken up, and then the water easily completes its work.  Sometimes in the soft, upper strata the systems of tunnel is extended, as in a coal-mine, by cross alleys, leaving blocks which are afterward washed away, and then the whole mass settles, and is disintegrated under the influence of water.  The wooden sluices in the tunnels already described are often made double for the convenience of “cleaning up” one of them, while the other remains in action.  The process of cleaning up is performed according to the quantity and richness of the material worked upon, at intervals of twenty to forty days, and consists in removing the pavement and blocks from the bed of the sluice, and then gathering all the amalgam of gold and rich dirt collected, and replacing the locks in the same way as at first.  Advantage is taken on this occasion to reverse the position of the blocks and stones when they are worn irregularly, or substitute new ones for those which are worn through.  The mechanical action of the washing process on the blocks is of course very rapid and severe, requiring complete renewal of them once in eight to ten weeks.  Some miners prefer a pavement of egg-shaped stones set like a cobble-stone flooring, the gold being deposited in the interstices.  Most of the sluiceways are, however, paved with rectangular wooden blocks, with or without stones as described.  Standing at the mouth of one of the long tunnels in full action, any