apart. The powder must, of course,
be provided with a fuse or preferably a fulminating cap. It is well to
insert the cap at or near the bottom of the cartridge, as shown in
Figs. 8 and 9.
After the charge the usual thing to do is to insert tamping. In the
improved form of hole the tamping should not he put directly upon the
powder, but an air space should be left, as shown at B, Fig. 8. The
best way to tamp, leaving an air space, is first to insert a wad,
which may be of oakum, hay, grass, paper or other similar material.
The tamping should be placed from 6 to 12 in. below the mouth of the
hole. In some kinds of stone a less distance will suffice, and as much
air space as practicable should intervene between the explosive and
the tamping. If several holes are used on a line they should be
connected in series and blasted by electricity. The effect of the
blast is to make a vertical seam connecting the holes, and the entire
mass of rock is sheared several inches or more.
The philosophy of this new method of blasting is simple, though a
matter of some dispute.
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