square, but in "liver" rock the holes must be drilled nearly
through the block and the size of the block first reduced.
A more difficult application of the system, and one requiring greater
care in its successful use, is where the block of stone is so situated
that both ends are not free, one of them being solidly fixed in the
quarry wall. A simple illustration of a case of this kind is a stone
step on a stairway which leads up and along a wall, Fig. 11. Each step
has one end fixed to the wall and the other free. Each step is also
free on top, on the bottom and on the face, but fixed at the back. We
now put one of the new form of holes in the corner at the junction of
the step and the wall. The shape of the hole is as shown in Fig. 12.
[Illustration: FIG. 11.]
It is here seen that the grooves are at right angles with each other,
and the block of stone is sheared by a break made opposite and
parallel with the bench, as in the previous case, and an additional
break made at right angles with the bench and at the fixed end of the
block.
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