furnace of the immense size to be presently given, but in 1884 it
erected a revolver only about 3 ft. to 4 ft. short of the length of
that one, and having two discharging holes. The giant revolving
furnace to be described measures in length 30 ft. and has a diameter
of 12 ft. 6 in. Inside length is 28 ft. 6 in., with a diameter of 11
ft. 4 in. It is lined with 16,000 fire bricks and 120 fire-clay blocks
or breakers, weighing each 1¼ cwt. The bricks weigh per 1,000 about
four tons. The weight of salt cake per charge (i.e., contained in
each charge of salt cake, limestone, mud, and slack) is 8 tons 12 cwt.
For 100 tons of salt cake charged, there are also charged about 110
tons of lime mud and limestone and 55 tons of mixing slack. In a week
of seven days about 48 charges are worked through, weighing of raw
materials about 25 _tons per charge_. The total amount of salt cake
decomposed weekly is about 400 tons, and may be reckoned as yielding
240 tons of 60 per cent. caustic soda. As regards fuel used for
firing, this may be put down as 200 tons per week, or about 10 cwt.
per ton of salt cake decomposed. Also with regard to the concentration
of liquor from 20° Tw. to 50° Tw., there is sufficient of such
concentrated liquor evaporated down to keep three self-fired caustic
pots working, which are boiled at a strength of 80° Tw. Were it not
for this liquor, no less than seven self-fired pots would be required
to do this work, showing a difference of 80 tons of fuel.

[Illustration: A NEW MONSTER REVOLVING BLACK ASH FURNACE. (2 Figures.) ]

The question may be asked, "Why increase the size of these huge pieces
of apparatus?" The answer, I apprehend, is that owing to competition
and reduction of prices, greater efforts are necessary to reduce
costs. With automatic apparatus like the black ash revolver, we may
consider no very sensible addition of man power would be needed, in