, a hole 11/2 in. in diameter was drilled in a block
which was 27 ft. long, 15 ft. wide and 6 ft. thick. The blast broke
the stone across the "rift," only 8 oz. of black powder being used. At
the Portland, Conn., quarries a single blast was fired by electricity,
15 holes being drilled with 2 lb. of coarse No. C powder in each hole,
and a rock was removed 110 ft. long, 20 ft. wide and 11 ft. thick,
containing 24,200 cu. ft., or about 2,400 tons, the fracture being
perfectly straight. This large mass of stone was moved out about 2 in.
without injury to itself or the adjoining rock.
Another blast at Portland removed 3,300 tons a distance of 4 in.
Seventeen holes were drilled, using 2 lb. of powder in each hole, the
size of the block being 150 x 20 x 11 ft. In a Lisbon, O., quarry a
block of sandstone 200 ft. long, 28 ft. wide and 15 ft. thick was
moved about 1/2 in. by a blast. This block was also afterward cut up by
this system in blocks 6 ft. square. A sandstone bowlder 70 ft. long,
average width 50 ft.
Pages:
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69