jrington.] OPEN-CUT MINING. 69 
The derrick in use at this plant is of a very simple and practical 
esign, there being but one haulage line, which with gravity utilized 
i the lean of the derrick accomplishes the desired work. The derrick 
sans toward the pit in which excavation is taking place — i. e., when 
t rest the boom swings away from the hoisting engine. (See PL 
L) The hauling line passes through a block at the foot of the mast 
ad a few feet in front of it, or toward the direction of haul. In this 
osition immediately upon receiving a hauling strain the boom tends 
) move toward the dump box, and once there, having disposed of its 
>ad, returns by gravity to the pit. To the end of the boom is attached 
rope by which a man in the pit giving his entire attention to this 
peration can regulate the swing of the boom to a nicety. By snub- 
ing this line about a post set firmly in the ground, hauls can be made 
1 any direction with no inconvenience from the swinging of the boom, 
rid the dumping of the load on the platform can be accurately 
ijusted. The derrick on an average lift raises material about 25 feet 
nd carries it approximately 85 feet to the sluices. The amount of 
laterial handled is generally 500 cubic yards in twenty -two hours, 
'ower is obtained from a 15-horsepower boiler and 8-horsepower 
ouble engine hoist, which burns one-half cord of wood in twenty - 
mv hours at $15 a cord. The derricks are of Washington fir, both 
oom and mast being 40 feet long. The hauling line, one-half inch 
i diameter, is of crucible steel wire, plow-share steel not bending 
isily enough, and the guy lines, three-eighths inch in diameter, also 
f steel, are tightened by watch tackles. 
Stones over 12 inches in diameter are not sent through the sluices, 
eing piled by hand in the center of the pit. Larger stones and 
owlders of bed rock are handled by the derrick and piled in the same 
tanner. (See PL IX, i>, p. 68.) The removal, however, of stones 
sceeding 2 tons in weight is not attempted with the derrick. A 
love is necessary each thirty days, and in advancing the entire plant 
pproximately 110 feet eighteen hours are generally consumed. An 
nxiliary flume and dump box must of necessity be used to permit 
ich rapid change. 
The dump box, which is furnished with a platform sufficiently large 
prevent spilling of material, is from 6 to 12 feet above the ground, 
is 16 feet long and has a grade of 14 inches. Below it are 132 feet 
boxes, 20 inches deep and 16 inches wide, with a grade of 7 inches 
the box length (12 feet). These are furnished with pole riffles 
ade 2 inches square, capped with iron, and will last two seasons. 
t the end of the string is a very efficient undercurrent, invented on 
e ground. It consists of an ordinary sluice box furnished with iron 
dts approximately three-eighths or one-half of an inch in diameter, 
nning lengthwise with the box and placed side by side. Beneath 
ese bars, held by Hungarian riffles, is a quantity of quicksilver, 
:i 
