ustration: Fig. 32.--Longitudinal section. Rill stope filled
with waste.]

[Illustration: Fig. 33.--Longitudinal section. Horizontal stope
filled with waste.]

[Illustration: Fig. 34.--Longitudinal section. Waste-filled stope
with dry-walling of levels and passes.]

In this system of stope support the ore is broken at intervals
alternating with filling. If there is danger of much loss from
mixing broken ore and filling, "sollars" of boards or poles are
laid on the waste. If the ore is very rich, old canvas or cowhides
are sometimes put under the boards. Before the filling interval,
the ore passes are built close to the face above previous filling
and their tops covered temporarily to prevent their being filled
with running waste. If the walls are bad, the filling is kept close
to the face. If the unbroken ore requires support, short stulls
set on the waste (as in Fig. 39) are usually sufficient until the
next cut is taken off, when the timber can be recovered. If stulls
are insufficient, cribs or bulkheads (Fig. 31) are also used and
often buried in the filling.

[Illustration: Fig. 35.--Cross-section of Fig. 34 on line _A-B_.]

Both flat-backed and rill-stope methods of breaking are employed in
conjunction with filled stopes. The advantages of the rill-stopes
are so patent as to make it difficult to understand why they are
not universally adopted when the dip permits their use at all. In
rill-stopes (Figs. 32 and 34) the waste flows to its destination
with a minimum of handling. Winzes and ore-passes are not required
with the same frequency as in horizontal breaking, and the broken
ore always lies on the slope towards the passes and is therefore
also easier to shovel. In flat-backed stopes (Fig. 33) winzes must
be put in every 50 feet or so, while in rill-stopes they can be
double this distance apart. The system is applicable by modification
to almost any width of ore. It finds its most economical field
where the dip of the stope floor is over 45 deg., when waste and ore,
with the help of the "rill," will flow to their destination. For
dips from under about 45 deg. to about 30 deg. or 35 deg., where the
waste and ore will not "flow" easily, shoveling can be helped by the
use of the "rill" system and often evaded altogether, if flow be
assisted by a sheet-iron trough described in the discussion of
stope transport. Further saving in shoveling can be gained in this
method, by giving a steeper pitch to the filling w