The system developed by Mr. Knox
practically does all and more than was done by the old
Portland system, and it does it at far less expense. It can
best be described by illustrations.
[Illustrations: Figs. 3, 4, 5, 6]
Fig. 3 is a round hole drilled either by hand or otherwise, preferably
otherwise, because an important point is to get it round. Fig. 4 is
the improved form of hole, and this is made by inserting a reamer,
Figs. 5 and 6, into the hole in the line of the proposed fracture,
thus cutting two V-shaped grooves into the walls of the hole. The
blacksmith tools for dressing the reamers are shown in Fig. 7. The
usual method of charging and tamping a hole in using the new system is
shown in Fig. 8. The charge of powder is shown at C, the air space at
B and the tamping at A. Fig. 9 is a special hole for use in thin beds
of rock. The charge of powder is shown at C, the rod to sustain
tamping at D, air space at BB, and tamping at A.
[Illustration: Fig. 7]
Let us assume that we have a bluestone quarry, in which we may
illustrate the simplest application of the new system.
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