year or two can be saved in getting to production
by entering the property at a higher horizon, the difference in
accumulated interest will more than repay the infinitesimal extra
cost of winding through a combined shaft of somewhat increased
length in the inclined section.

The unknown character of the ore in depth is always a sound reason
for reaching it as quickly and as cheaply as possible. In result,
such shafts are usually best located when the vertical section
enters the upper portion of the deposit.

The objective in location with regard to the strike of the ore-bodies
is obviously to have an equal length of lateral ore-haul in every
direction from the shaft. It is easier to specify than to achieve
this, for in all speculative deposits ore-shoots are found to pursue
curious vagaries as they go down. Ore-bodies do not reoccur with
the same locus as in the upper levels, and generally the chances
to go wrong are more numerous than those to go right.

NUMBER OF SHAFTS.--The problem of whether the mine is to be opened
by one or by two shafts of course influences location. In metal
mines under Cases II and III (outcrop properties) the ore output
requirements are seldom beyond the capacity of one shaft. Ventilation
and escape-ways are usually easily managed through the old stopes.
Under such circumstances, the conditions warranting a second shaft
are the length of underground haul and isolation of ore-bodies or
veins. Lateral haulage underground is necessarily disintegrated by
the various levels, and usually has to be done by hand. By shortening
this distance of tramming and by consolidation of the material
from all levels at the surface, where mechanical haulage can be
installed, a second shaft is often justified. There is therefore
an economic limitation to the radius of a single shaft, regardless
of the ability of the shaft to handle the total output.

Other questions also often arise which are of equal importance
to haulage costs. Separate ore-shoots or ore-bodies or parallel
deposits necessitate, if worked from one shaft, constant levels
through unpayable ground and extra haul as well, or ore-bodies may
dip away from the original shaft along the strike of the deposit
and a long haulage through dead levels must follow. For instance,
levels and crosscuts cost roughly one-quarter as much per foot as
shafts. Therefore four levels in barren ground, to reach a parallel
vein or isolated ore-body 1,000 feet away, wou