sible lines of improvement in winding is in the
direction of larger loads and less speed, for in this way the sum
total of dead weight of the vehicle and rope to the tonnage of
ore hauled will be decreased, and the efficiency of the engine
will be increased by a less high peak demand, because of this less
proportion of dead weight and the less need of high acceleration.

LATERAL UNDERGROUND TRANSPORT.

Inasmuch as the majority of metal mines dip at considerable angles,
the useful life of a roadway in a metal mine is very short because
particular horizons of ore are soon exhausted. Therefore any method
of transport has to be calculated upon a very quick redemption of
the capital laid out. Furthermore, a roadway is limited in its
daily traffic to the product of the stopes which it serves.

MEN AND ANIMALS.--Some means of transport must be provided, and
the basic equipment is light tracks with push-cars, in capacity
from half a ton to a ton. The latter load is, however, too heavy
to be pushed by one man. As but one car can be pushed at a time,
hand-trucking is both slow and expensive. At average American or
Australian wages, the cost works out between 25 and 35 cents a
ton per mile. An improvement of growing import where hand-trucking
is necessary is the overhead mono-rail instead of the track.

If the supply to any particular roadway is such as to fully employ
horses or mules, the number of cars per trip can be increased up
to seven or eight. In this case the expense, including wages of
the men and wear, tear, and care of mules, will work out roughly
at from 7 to 10 cents per ton mile. Manifestly, if the ore-supply
to a particular roadway is insufficient to keep a mule busy, the
economy soon runs off.

MECHANICAL HAULAGE.--Mechanical haulage is seldom applicable to
metal mines, for most metal deposits dip at considerable angles,
and therefore, unlike most coal-mines, the horizon of haulage must
frequently change, and there are no main arteries along which haulage
continues through the life of the mine. Any mechanical system entails
a good deal of expense for installation, and the useful life of
any particular roadway, as above said, is very short. Moreover,
the crooked roadways of most metal mines present difficulties of
negotiation not to be overlooked. In order to use such systems it
is necessary to condense the haulage to as few roadways as possible.
Where the tonnage on one level is not sufficient to warrant oth