By means of a machine like a pile driver, this monstrous tool is
raised to a height of about fifty feet, and allowed to drop, point
first. So heavy a mass of metal, falling from a considerable height,
meets with comparatively little resistance from the water, and the
point shatters and grinds up the rock on which it strikes. Fifty or
sixty blows per minute can be struck with a tool of this kind, and ten
thousand blows in all can be inflicted before the tool is so worn as
to be past service. Several of these drills will be at work at the
same time, and to remove the fragments of rock which they break off, a
huge dredge of three hundred and fifty horse power is to be employed.
For excavating by means of explosives, arrangements have been made for
drilling the holes for the cartridges with the greatest possible
rapidity, as on this depends the celerity with which the work can be
pushed forward. Much of the work will be done by means of diamond
drills, which are mounted on boats. Five of these boats have been
provided, each with seven diamond drills, arranged so as to work
perfectly in twenty feet of water. Other boats are fitted with
pneumatic drills, which are operated by means of air, compressed to a
tension of seven hundred and fifty pounds to the square inch.
Pages:
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57