gaseous
fuel firing, a very considerable economy in fuel and in repairs to
furnace, and a superior roasting effect, have been obtained.

Where the ordinary reverberatory hearth is fired with solid coal from
an end grate, the temperature is at its maximum near the firing end, and
tails off at the extreme gas outlet end. The ores in this furnace should
therefore be fed in at the colder end of the hearth and be gradually
worked or "rabbled" forward to the firing end.

One disadvantage of the reverberatory furnace is the fact that it is
impossible to avoid the incursion of air during the manual rabbling
action, and this tends to cool the furnace.

The cost of roasting, to obtain the more or less complete oxidation, or
what is known in mining parlance as a "sweet roast" (because a perfectly
roasted ore is nearly odourless) varies considerably, the variation
depending of course upon the character of the ore and the cost of labour
and fuel.

There are several modifications of the reverberatory furnace in use,
designed mechanically to effect the rabbling. One of the most successful
is that known as the Horse-shoe furnace. In plan the hearth of the
furnace resembles a horse-shoe.

The stirring of the ore over the hearth is effected by means of
carriages fixed in the centre of the furnace and having laterally
projecting arms, carrying stirrers, that move along the hearth and turn
over the pulverised ore.

In operation, half the carriages are traversing the furnace, and half
are resting in the cooling space, so that a control over the temperature
of the stirrers is established.

This furnace is stated to be more economical in labour than other
mechanically stirred reverberatory furnaces, and there is also said to
be an economy in fuel.

Usually the mechanical stirring furnaces give trouble and should be
avoided, but the horse-shoe type possesses qualifications worthy of
consideration.

"B."--THE REVOLVING CYLINDER FURNACE.

Of these the best known to me are: The Howell-White, the Bruckner, the
Thwaite-Denny, and the Molesworth.

The Bruckner is a cylinder, turning on the horizontal axis and carried
by four rollers.

The batch of ore usually charged into the two charging hoppers weighs
about four tons. When the two charging doors are brought under the
hopper mouth, the contents of the hopper fall directly into the
cylinder.

The ends or throats of the furnace are reduced just sufficiently to
allow the flame evol