was
325 feet long. Commencing at the upper end ol the drift, a cross drift
was run 80 feet to the right and 120 feet to the left. Five additional
cross drifts of similar length were driven from the main drift 50 feet
apart, the last one being opened at a point 75 feet distant from the
entrance of the tunnel. There were three lifters in this last cross
drift, two in the left arm and one at the end of the right arm. The
main drift was tamped from the entrance to the first cross-drift. The
drifts were 3 by 4 feet in size. The blast was simultaneously fired at
ten different points by electricity. The mass shattered was reported as
200 feet long, 150 feet wide, and 73 feet deep.
At the Enterprise Mine, Nevada County, with 250 feet bank, a blast of 1,700 kegs was fired.
Paragon Mine Blast.—In
1874 there was a blast of 700 kegs black powder set off at the Paragon
Mine, Placer County. The details of the drifts arranged for the blasts
are shown in Fig. 60.
The
main drift, A, was tamped for 75 feet from the near end, and the cross
drifts tamped 10 feet each way, a space being left in the lifters for
the expansion of the gas generated by the explosion of the powder. The
drifts were 4-1/2 feet high and 5 feet wide, and the bank was
150 high. The blast was fired by electricity, and the ground covered by
the drifts was thoroughly shattered.
A
blast of 3,500 pounds of giant powder No. 2 was fired, in 1872, in the
Harriman and Taylor claim at Gold Run, Placer County, and is reported
to have thrown down 200,000 cubic yards of gravel.
Dardanelles Mine Blast.—At
the Dardanelles Hydraulic and Drift Mine near Forest Hill, Placer
County, a blast was made with 36,400 pounds of Judson powder (old),
shattering about 500,000 cubic yards of cement gravel. The gravel bank
had a face of some 1,200 feet in length, with a height of 175 feet.
This deposit reposed on a rising bed-rock. Five parallel drifts, 180
feet apart, were run in from the face a length of 70 feet each. From the
