purington.] HYDRAULIC MINING. 115 
then tilled in between the lagging and the side of the ditch, poles laid 
lengthwise over the caps, and sod laid over i\w whole. Fluming has 
been found very unsatisfactory at the Treadwell. The flume was 
banked with sod on sides and top. Anchor ice in winter collected in 
the bottom of the flume, and was removed with great difficulty. 
The Treadwell ditch for long distances is bridged with poles and 
brush, which in many places are covered with sods. Sodding is said 
to be the besk preventive against freezing, not only here, but in all 
parts of Alaska. 
The pressure boxes are connected with the ditch by flumes 35 feet 
long, 5 feet wide, and 3 feet deep. The water first enters a gravel 
tank which is cleaned twice a year. This tank is built of 2-inch lum- 
ber and is 8 feet wide by 9 feet long and 14 feet deep. From the tank 
the water flows through a 4-foot section of flume 3 feet 3 inches wide, the 
bottom of which is only 5 feet below the top of the tank, into the main 
penstock. This is 11 feet long by 9i feet wide, inside measurement, 
and 14 feet deep. It is built of 3-inch lumber, with 8- by 10-inch posts, 
sills, and caps, with 4-foot centers. The penstock is fitted with a 
wooden inclined grizzly to catch any leaves or refuse that pass the 
."•ravel trap. The penstock and sand trap combined make a structure 
>A) feet 6 inches long by 10 feet 10 inches wide by 14 feet deep, out- 
side measurement. The penstock, as illustrated in PL XVII, A, is 
ranked halfway up the sides with sod, and the pipe line leading from 
t is covered with sod. The sand trap is provided with a sluicing-out 
rate on the side opposite that shown by the photograph. a 
PL XVII, B, illustrates a method of guying the pressure box on 
teep slope, in use by the American Gold Mining Company in Silver 
3ow r basin, Alaska. The intake of the pipe line is protected by shed 
rom heavy snows. 
As water is in use for placer mining only during the open season, 
ew instances were seen in Alaska of attempts to sod up the ditches 
nd connections to prevent freezing in winter. At the Treadwell, 
owever, the water is used for generating power. Pipe lines, 
specially in Seward Peninsula, are frequently sodded over, as much 
or protection against rust as to prevent freezing. 
In Silver Bow basin, east of Juneau, ditching has been found imprac- 
cable and all conduits are flumed. In general in southeastern Alaska 
uming will be found cheaper than ditching, as ditches would have to 
e cut in solid rock for the most part, and in numerous places the 
lountain slopes are so steep as to render their construction impossible. 
a See Bowie, A. J., jr., A Practical Treatise on Hydraulic Mining in California, 1885, p. 177, for plan 
id elevation of North Bloomfield pressure box. 
