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tion into this furnace shaft, greatly increasing
tne motive column.
Ashton Moss colliery in Lancashire, England,
with a shaft nearly 1,000 yards deep, is ventilated
by a furnace. The writer has no statistics of
the ventilating of this colliery, but from personal
observation, he would not think it approached in
volume many of the better furnace ventilated pits
in the county of Durham. At 1,000 yards deep,
with well designed furnaces, the economy should
approach, if not reach, that of any of our best
modern fans.
At Rose Bridge, another deep mine in Lancashire
still using the furnace, four seams are ventilated,
and the volume of air exceeds 200,000
cubic feet per minute, (shaft 810 yards deep).
The last time the writer descended this shaft, now
over 25 years ago. it was suggested that he accept
the loan of a very heavy flannel jacket and turn
up the collar to pass the furnace drift mouthing?.
Afterwards he was thankful for the loan.
In the construction of furnaces, the general
plan was to build a central arch for the grate and
furnace proper, and two side arches for the purposes
of firing and cleaning the rear end of the
furnace, which had sometimes 50 feet in length
of grate bars by 10 feet wide. These arches were
usually backed overhead, next to the strata, with
sand. Adjustable iron doors at the front, and a
fire brick lined drift to the shaft at the rear,
completed the equipment of an ordinary furnace.
The best practice, however, was to throw a
large arch over the space intended to enclose the
furnace, and build the three interior arches
within it as described above. In a furnace so
constructed, the writer saw checker work of flre
brick over the flre, before he had seen a Siemens
furnace, the mine furnaces performing the same
functions of conserving heat as does the Siemens
furnace, with which you gentlemen are all so
familiar. Two furnaces were often placed side
by side, but delivering into a common furnace
drift, one being kept white hot while the other
was being cleaned.
From 1850 to 1860 the mine furnace received its
greatest development. In mines where the return
air was so highly charged with explosive gas as
to render it dangerous to pass tne returns over
the furnace fire, an arrangement called a "dumb
drift" was used. This was an inclined road
driven from a point in the rear of the furnace,
and in its best form separated from it by solid
strata, entering the shaft at a point sufficiently
high above the furnace drift to prevent ignition
of the fire damp from the flame of the furnace.
In some pits only part of the air was passed
through the duml) drift, and the returns considered
safe were passed directly over the furnace
fire. The best practice, however, was to feed
the furnace with fresh air direct from the bottom
THE COAL TRADE BULLETIN. .31
of the down cast pit, and pass all returns through
the dumb drift.
The danger remaining was the liability to fire
soot in the furnace flue below and cause it to
blaze out the shaft. This soot was cleaned out
during stoppage of the mine, from holidays or
other causes, and the writer well remembers doing
the somewhat disagreeable duty of "sitting a
horse" at the mouth of the dumb drift, watching
with a safety lamp for fire damp, while the men
were sweeping out the soot from me furnace drift
below.
The statistics available, showing coal consumption
in furnace ventilation, are not very reliable,
"Sitting a Horse" at the Mouth of the Dumb Drift.
as in most cases where furnaces were in use, the
up-cast shaft was used as a chimney for underground
boilers whose consumption was not generally
taken into account. The consumption of
coal per H. P. in the air, varied in every case with
the depth of the shaft. For instance, Pelton
colliery, Durham, England, with a depth of 106
yards, the consumption of coal per H. P. per hour
in air is given as 09.8 pounds, while at Ryhope,
where the shaft is 460 yards deep, the consumption
is given as 26.2 pounds.
With the best furnaces it was found that coal
was burnt very wastefully, and as early as 70
years ago, attempts were made to substitute mechanical
for thermal ventilation. One pet idea
was to use the jet like a crude kind of Koerting
blower, placed in the mine shaft with its mouth