eys. The advantage of wrought-iron
or steel chimneys lies in the convenience of removal and erection. They
should be made in sections of 20 feet long, three steel wire guy-ropes
attached to a ring, riveted to a ring two-thirds of the height of the
chimney, and attached to holdfasts driven into the ground; tightening
couplings should be provided for each wire.

Flue dust depositing chambers should be built in the line of the flues
between the furnace and the chimney; they consist simply of carefully
built brick chambers, with openings to enable workmen to enter and
rapidly clear away the deposited matters. The chambers, three or four
times the cross sectional area of the chimney flue, and ten to twenty
feet long, can be built of brickwork, set in cement; the walls are
provided with a cavity, filled with sand or Portland cement, so that
there will be no danger of the incursion of air. In all furnace work
the greatest possible precautions should be taken to prevent the least
cracking of either joints or bricks. It is surprising how much the
inadequate draft of a good chimney is due to cracks or orifices in the
flues; and therefore a competent furnace-man should see to it that his
flues are thoroughly sound, and free from openings through which the air
can enter.[*]

[*] For full details of the most recent improvements in the
cyanide process and in other methods of extraction, the
reader is referred to Dr. T. K. Rose's "Metallurgy of Gold,"
third edition.

CHAPTER IX

MOTOR POWER AND ITS TRANSMISSION

It is unnecessary to describe methods by which power for mining purposes
has been obtained--that is, up to within the last five years--beyond
a general statement, that when water power has been available in the
immediate locality of the mine, this cheap natural source of power has
been called upon to do duty. Steam has been the alternative agent of
power production applied in many different ways, but labouring under as
many disadvantages, chief of which are lack of water, scarcity of fuel
and cost of transit of machinery. Sometimes condensing steam-engines
have been employed. For the generation of steam the semi-portable and
semi-tubular have been the type of boiler that has most usually been
brought into service. Needless to say, when highly mineralised mine
water only is available the adoption of this class of boiler is attended
with anything but satisfactory results.

Recently, however, the