The
arrangement of the powder chambers for a 1,201-keg blast made by the
Smartsville Hydraulic Mining Company in December, 1868, is shown in the
following diagram.
X was a shaft 74 feet deep, from the bottom of which the main drift, A, was driven 185 feet. The cross drifts,
B,
three in number, were driven at distances respectively of 70 feet, 120
feet, and 170 feet from the shaft, X. They extended each 20 feet on one
side of the main drift and 40 feet on the other side. The several
drifts marked C are called "lifters." Each " lifter " was 15 feet long.
The total length of the drifts aggregated 570 feet. They were 2-1/2 feet
wide and 3-1/2 feet high. The cross drifts were charged with 1,201 kegs
(25 pounds each) of black powder. The main drift was securely tamped
from the shaft to the first cross drift, a distance of 70 feet. The
powder was simultaneously ignited by electricity at 12 different
points.
The ground moved was 270 feet long, 180 feet wide, with an average depth of 100 feet. The cost of the blast was about $6,000.
Blue Point Blast.—A large blast of 2,000 kegs (25 pounds each) was exploded December 29, 1870, at the Blue Nevada County. The main drift
