It is much better, however, to release the
"pressure" from the ledge by channeling, after which a single end may
be detached by a Knox blast. It is well to bear in mind that the holes
should invariably be of small diameter. In no case should the diameter
of a hole be over 11/2 in. in any kind of rock. This being the case, the
blocks of stone are delivered to the market with but little loss in
measurement. It is a noticeable fact that stone quarried by the new
system shows very little evidence of drill marks, for the faces are
frequently as true as though cut with a machine.
A further gain is the safety of the system. The blasting is light and
is confined entirely within the holes. No spalls or fragments are
thrown from the bast.
The popular idea that the system is antagonistic to the channeling
process is a mistaken one. There are, of course, some quarries which
formerly used channeling machines without this system, but which now
do a large part of the work by blasting. Instances, however, are rare
where the system has replaced the channeler.
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