192 
GRAVEL AND PLACER MINING IN ALASKA. 
[bull. 263. 
derrick skips dump into the mud box, a platform, inclined at an 
angle of about 50°, 9 feet square, and built up of timber floored with 
rough scantling, is erected on the side of the box for the gravel to 
fall on. 
The capacity of the sluice is cut down rather than increased by the 
use of the mud box, and the expense is increased by the cost of the 
man. A greater saving of gold is made, but at best the operation is 
expensive and of small and variable efficiency. In some shoveling-in 
operations the use of the mud box is advisable, but where mechanical 
self -dumping buckets are used, it is possible that some other form of 
agitator might be advantageously employed. 
The developments of the open-cut and drifting methods of gravel 
mining have necessitated an enlarging of the sluicing capacity. With 
Plan 
^-^1 
LMJ 
uu 
w 
A 
Grade ,6 to 12" in 12' 
Side elevation 
Front elevation 
Rear elevation 
Scale 
O 1 
i feet 1 
Flume 
intake 
\ 
\ 
i i i i 
G. 40. — Mud box. 
the enlarging of the capacity, however, there has not been a propor- 
tionate improvement in the construction of the gold-saving appliances. 
In other words, instead of drawing on the experience of the hydraulic 
miner and the dredge miner for the adoption of gold-saving methods, 
the creek miners of the Klondike have continued the method of the 
long, narrow sluice used for shoveling-in operations, amplifying its 
error and suffering the inevitable losses of fine gold which its use 
entails. 
The average capacity of a small placer operation where hand labor 
is employed is 40 cubic yards a day of ten hours. Grant that the nar- 
row sluice of 36 feet in length with pole riffles is most economical for 
the needs of such a mine. Now take an average summer drifting 
