ume of the ore, and the size of the load.
For shallow depths and tonnages up to, say, 200 tons daily, geared
engines have a place on account of their low capital cost. Where
great rope speed is not essential they are fully as economical as
direct-coupled engines. With great depths and greater capacities,
speed becomes a momentous factor, and direct-coupled engines are
necessary. Where the depth exceeds 3,000 feet, another element
enters which has given rise to much debate and experiment; that
is, the great increase of starting load due to the increased length
and size of ropes and the drum space required to hold it. So far
the most advantageous device seems to be the Whiting hoist, a
combination of double drums and tail rope.

On mines worked from near the surface, where depth is gained by
the gradual exhaustion of the ore, the only prudent course is to
put in a new hoist periodically, when the demand for increased
winding speed and power warrants. The lack of economy in winding
machines is greatly augmented if they are much over-sized for the
duty. An engine installed to handle a given tonnage to a depth of
3,000 feet will have operated with more loss during the years the
mine is progressing from the surface to that depth than several
intermediate-sized engines would have cost. On most mines the
uncertainty of extension in depth would hardly warrant such a
preliminary equipment. More mines are equipped with over-sized
than with under-sized engines. For shafts on going metal mines
where the future is speculative, an engine will suffice whose size
provides for an extension in depth of 1,000 feet beyond that reached
at the time of its installation. The cost of the engine will depend
more largely upon the winding speed desired than upon any other
one factor. The proper speed to be arranged is obviously dependent
upon the depth of the haulage, for it is useless to have an engine
able to wind 3,000 feet a minute on a shaft 500 feet deep, since it
could never even get under way; and besides, the relative operating
loss, as said, would be enormous.

HAULAGE EQUIPMENT IN THE SHAFT.--Originally, material was hoisted
through shafts in buckets. Then came the cage for transporting mine
cars, and in more recent years the "skip" has been developed. The
aggrandized bucket or "kibble" of the Cornishman has practically
disappeared, but the cage still remains in many mines. The advantages
of the skip over the cage are many. Some of th