clear. In blocking out the stopes, the uprights are 6 feet 2
inches, just one foot shorter than those in the main drives.
The caps and struts are of the same dimensions and timber as
the sill floor. The planks used as staging are 9 inches by 2½
inches; they are moved from place to place as required, and
upon them the men stand when working in the stopes and in the
faces. A stope resembles a huge chamber fitted with
scaffolding from floor to roof. The atmosphere is cool and
pure, and there is no dust. Stage is added to stage, according
as the stoping requires it, and ladders lead from one floor to
the other; the accessibility to all the faces is a great
advantage.

If, while driving, a patch of low grade ore is met with, it
can be enriched by taking a higher class from another face,
and so on. Any grade can be produced by means of this power of
selection. Opinions have been expressed that this system of
timbering is not secure, and that pressure from above would
bring the whole structure down in ruins. But an opinion such
as this is due to miscomprehension of the facts. If signs of
weakening in the timbers become apparent, the remedy is very
simple. Four or more of the uprights are lined with planks,
and waste material is shot in from above, and a strong support
is at once formed, or if signs of crushing are noticed, it is
possible to go into the stope, break down ore, and at once
relieve the weight."

[Illustration: THE SQUARE SYSTEM OF TIMBERING IN MINES.]

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