loose ore will lodge on
the foot wall. Stopes opened in this manner when partially empty
are too dangerous for men to enter for shoveling out remnants.

The advantages of this system over others, where it is applicable,
are:--

(_a_) A greater distance between levels can be operated and few
winzes and rises are necessary, thus a great saving of development
work can be effected. A stope 800 to 1000 feet long can be operated
with a winze at either end and with levels 200 or 220 feet apart.

(_b_) There is no shoveling in the stopes at all.

(_c_) No timber is required. As compared with timbering by stulling,
it will apply to stopes too wide and walls too heavy for this method.
Moreover, little staging is required for working the face, since
ore can be drawn from below in such a manner as to allow just the
right head room.

(_d_) Compared to the system of filling with waste, coincidentally
with breaking (second method), it saves altogether in some cases
the cost of filling. In any event, it saves the cost of ore-passes,
of shoveling into them, and of the detailed distribution of the
filling.

Compared with other methods, the system has the following disadvantages,
that:

_A_. The ore requires to be broken in the stopes to a degree of
fineness which will prevent blocking of the chutes at the level.
When pieces too large reach the chutes, nothing will open them but
blasting,--to the damage of timbers and chutes. Some large rocks
are always liable to be buried in the course of ore-breaking.

_B_. Practically no such perfection of walls exists, but some spalling
of waste into the ore will take place. A crushing of the walls
would soon mean the loss of large amounts of ore.

_C_. There is no possibility of regulating the mixture of grade
of ore by varying the working points. It is months after the ore
is broken before it can reach the levels.

_D_. The breaking of 60% more ore than immediate treatment demands
results in the investment of a considerable sum of money. An equilibrium
is ultimately established in a mine worked on this system when a
certain number of stopes full of completely broken ore are available
for entire withdrawal, and there is no further accumulation. But,
in any event, a considerable amount of broken ore must be held in
reserve. In one mine worked on this plan, with which the writer
has had experience, the annual production is about 250,000 tons
and the broken ore represents an investment whi