144 GRAVEL AND PLACER MINING IN ALASKA. [bull. 263. 
The amount of lumber in a sluice box like that figured is as follows: 
8 posts, 4 by 4 inches by 3| feet. 
4 sills, 4 by 6 inches by 6 feet. 
16 braces, 1J by 4 inches by 1 foot. 
1 top rail, 1£ by 8 inches by 12 feet. 
16 post straps, H by 2 by 4 inches. 
3 bottom boards, 1£ by 8 inches by 12 feet. 
1 bottom board, 1£ by 4 inches by 12 feet. 
4 side boards, 1 by 8 inches by 12 feet. 
6 side boards, 1? by 8 inches by 12 feet. 
2 lining boards, 1£ by 8 inches by 12 feet. 
48 riffle blocks, 8 by 8 by 12 inches. 
16 riffle strips, 1 by 3 by 28 inches. 
Each box, with riffle blocks, contains approximately 540 feet of 
lumber. 
The use of 8-inch lumber is a necessity if native timber is used, 
12- inch lumber being very scarce and the expense of employing it 
prohibitive. The cost of each box, including riffles, averages $25, 
sluice lumber being $45 per thousand and the riffle blocks costing $6 
per box length. The setting of the riffle blocks with alternate spac- 
ing, as represented, is said to be advantageous, causing a cross circu- 
lation and consequent stirring action. The riffles are nailed in sets 
of three to a riffle strip outside the flume, and are piled up ready to be 
put in position as occasion demands. Pole riffles, 12 feet in length, made 
of 3- by 3-inch strips, set with a right-angle uppermost and shod with 
angle iron, are used in a portion of the boxes. A space is left between 
the lowest angle and the bottom of the box, the long strips being set 
with a gain into cross strips, 6 feet apart. The blocks are being grad- 
ually replaced by this type of pole riffle. The gold is coarse, and il 
is said that undercurrents would be of no advantage. In the first bos 
85 per cent of the gold is caught. In the first five boxes all the 
gold is caught which pays to clean up. In one clean-up $25,000 wa^ 
caught in the first box, as against $1,900 in the remainder of the 700 
foot sluice. The clean-up of the upper two boxes takes place once h 
two weeks. In this sluice the miner's inch is said to have a duty of i 
yards. A new box is put on the end of the tail sluice ever} T tw( 
days. When the end of the sluice is spread into Y's, a hinged gate 
with steel plates on both sides, is used for diverting the water an( 
tailings into one or the other branches. 
Experience on McKee Creek appears to show that the gold is savec 
in a comparatively short distance. Yet gravel miners in Californii 
maintain, and with apparent reason, that the longer the sluice th< 
more gold will be saved. For example, at the Hidden Treasure drif 
mine, in Eldorado County, Cal., it was stated to the writer that tin 
2,500 feet of sluice boxes, 19 by 21 inches in the clear, with iron ca 
wheel and rack riffles, and an undercurrent attached, were insuflicien 
