1out
because of the hardness or other difficulty, and the drift or tunnel is
low, a heap of dried logs is placed against the rock and fired; if the drift or
tunnel is high, two heaps are necessary, of which one is placed above the
other, and both burn until the fire has consumed them. This force does not
generally soften a large portion of the vein, but only some of the surface.
When the rock in the hanging or footwall can be worked by the iron tools
and the vein is so hard that it is not tractable to the same tools, then the
walls are hollowed out; if this be in the end of the drift or tunnel or above
or below, the vein is then broken by fire, but not by the same method; for
if the hollow is wide, as many logs are piled into it as possible, but if narrow,
only a few. By the one method the greater fire separates the vein more
completely from the footwall or sometimes from the hangingwall, and by the
other, the smaller fire breaks away less of the vein from the rock, because in
that case the fire is confined and kept in check by portions of the rock which
surround the wood held in such a narrow excavation. Further, if the
excavation is low, only one pile of logs is placed in it, if high, there are
two, one placed above the other, by which plan the lower bundle being
kindled sets alight the upper one; and the fire being driven by the draught
into the vein, separates it from the rock which, however hard it may be, often
becomes so softened as to be the most easily breakable of all. Applying this
principle, Hannibal, the Carthaginian General, imitating the Spanish miners,
low, a heap of dried logs is placed against the rock and fired; if the drift or
tunnel is high, two heaps are necessary, of which one is placed above the
other, and both burn until the fire has consumed them. This force does not
generally soften a large portion of the vein, but only some of the surface.
When the rock in the hanging or footwall can be worked by the iron tools
and the vein is so hard that it is not tractable to the same tools, then the
walls are hollowed out; if this be in the end of the drift or tunnel or above
or below, the vein is then broken by fire, but not by the same method; for
if the hollow is wide, as many logs are piled into it as possible, but if narrow,
only a few. By the one method the greater fire separates the vein more
completely from the footwall or sometimes from the hangingwall, and by the
other, the smaller fire breaks away less of the vein from the rock, because in
that case the fire is confined and kept in check by portions of the rock which
surround the wood held in such a narrow excavation. Further, if the
excavation is low, only one pile of logs is placed in it, if high, there are
two, one placed above the other, by which plan the lower bundle being
kindled sets alight the upper one; and the fire being driven by the draught
into the vein, separates it from the rock which, however hard it may be, often
becomes so softened as to be the most easily breakable of all. Applying this
principle, Hannibal, the Carthaginian General, imitating the Spanish miners,