ssible
partially to equalize matters. Therefore the size of inclines for
the same output need not differ materially from vertical shafts.

The maximum capacity of a shaft whose equipment is of the character
and size given above, will, as stated, decrease somewhat with extension
in depth of the haulage horizon. At 500 feet, such a shaft if vertical
could produce 70 to 80 tons per hour comfortably with an engine
whose winding speed was 700 feet per minute. As men and material
other than ore have to be handled in and out of the mine, and
shaft-sinking has to be attended to, the winding engine cannot
be employed all the time on ore. Twelve hours of actual daily
ore-winding are all that can be expected without auxiliary help.
This represents a capacity from such a depth of 800 to 1,000 tons
per day. A similar shaft, under ordinary working conditions, with
an engine speed of 2,000 feet per minute, should from, say, 3,000
feet have a capacity of about 400 to 600 tons daily.

It is desirable to inquire at what stages the size of shaft should
logically be enlarged in order to attain greater capacity. A
considerable measure of increase can be obtained by relieving the
main hoisting engine of all or part of its collateral duties. Where
the pumping machinery is not elaborate, it is often possible to
get a small single winding compartment into the gangway without
materially increasing the size of the shaft if the haulage compartments
be made somewhat narrower (Fig. 10). Such a compartment would be
operated by an auxiliary engine for sinking, handling tools and
material, and assisting in handling men. If this arrangement can
be effected, the productive time of the main engine can be expanded
to about twenty hours with an addition of about two-thirds to the
output.

Where the exigencies of pump and gangway require more than two
and one-half feet of shaft length, the next stage of expansion
becomes four full-sized compartments (Fig. 11). By thus enlarging the
auxiliary winding space, some assistance may be given to ore-haulage
in case of necessity. The mine whose output demands such haulage
provisions can usually stand another foot of width to the shaft,
so that the dimensions come to about 21 feet to 22 feet by 7 feet
to 8 feet outside the timbers. Such a shaft, with three- to four-ton
skips and an appropriate engine, will handle up to 250 tons per
hour from a depth of 1,000 feet.

The next logical step in advance is the shaft o