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32 THE COAL TRADE BULLETIN.
upward. This idea received the endorsement of
many eminent mining men and a Royal Commission
of the day, but tlie result was a most dismal
failure.
Displacement blowers like Lemeille and Fabry,
and tlie huge piston machines like Struve and
Nixon, which though of Belgian origin received
their greatest development in South Wales, continued
in use until about forty years ago (indeed
the Struve survived much later at Risca, South
Wales). But when the chimney and shutter invented
by Guibal was placed over a Nasmyth
fan at Tursdale. it showed that the centrifugal
fan was the mine ventilator of the future. This,
coming at a time when colliery explosions were
so common and sweepingly fatal in Europe, gave
tne Guibal fan an excellent entry into the confi­
dence of mine owners, and from a European standpoint
it has well justified that confidence. The
weakness of construction, however, unfavorable
to high speed, compelled mining men to stick doggedly
and tenaciously to slow running fans. In­
creased areas, and consequently increased resistance
to the passage of air in mines, was met by
increased diameter of fans, with a climax of one
50-ft. diameter at St. Hilda colliery. South Shields,
England. Our anthracite friends, in a measure,
have sought to emulate European practice with
less success except in the few cases where Guibal
models have been strictly adhered to. But both
in England and America, outside the hard coal
regions, we have abandoned the idea of getting
over the ground with a cart horse, and have de­
cided that a race horse is what we need to win.
The development of electrical machinery has
had much to do with the new departure in fans.
and the writer would venture to predict that the
electric mine fan of the future is one that will
be direct coupled to the motor.
In twenty years the speed of fans has increased
from about 40 R. P. M. to 200 R. P. M., and diameters
diminished from 50 feet (and very commonly
46 feet) to 16 feet, with results which have surprised
even advocates of high speed. A 45-foot
Guibal fan at Back worth was replaced by a 13-ft.
6-in. Capell fan and 50 per cent, more air passed
at twice the resistance. With fans 16 feet in
diameter we have obtained duties which no Guibal
fan on earth ever did, or ever could do.
A Clifford-Capell fan-;- 25 feet in diameter, running
128 R. P. M. at the Lambert mine, gave a
ventilation of 418,000 cubic feet of air per minute
at a mine resistance equal to 6.2 inches of water
gauge. At Briar Hill mine, Uniontown, Pa., we
have passed 462,000 cubic feet of air per minute
at a resistance of 7.08 inches water gauge, with
a fan 18 feet in diameter, running at 190 R. P. M.,
with a mechanical efficiency of 79.2 per cent, on
IA comprehensive cut of a Clifford-Capell Fan is shown on page
18 of this issue of THK COAI. TKADB BULLETIN.
the indicated horse power of the engine, and the
duty could have been steadily maintained.
The outlines of ventilation should include some
description of the arrangement of underground
workings, but the length of the paper forbids more
than a passing reference. The over-cast or air
crossing is one of the most important things underground,
and its location, size, strength and outlines,
are matters for serious consideration of the
mining engineers.
About the period referred to as the advent of
the Guibal fan, some engineers in England pro­
posed to drive all main air crossings through the
solid strata, above or below the road crossed.
'fhe writer has personal knowledge of only one
mine (Monk Bretton) where this was done.
When an explosion occurs it has been commonly
found that the over-cast is blown down, and consequently
the circulation of air cut off from per­
sons within the mine. Where this is the case,
after-damp gets in its deadly work on those who
have escaped from the heat, or force, of the blast.
In explosions of forty years ago, deaths mainly
resulted from after-damp, the force of the explosion
having been modified by the lack of air to
support combustion. Very limited observations
during twenty years past, and all my reading,
lead me to conclude that the great bulk of deaths
in colliery explosions during that period are from
burning. We do not now get explosions so often,
but when we do get them they are usually detonating
explosions.
In conclusion tne writer ventures to say:
(a) That the air entering a mine should not
have a greater velocity than 2,000 feet per minute
in the down-cast shaft.
(b) The main airways, from the bottom of the
shaft to the first split, should have a combined
area equal to one-third greater than that of the
shaft.
lc) The cross section, at the top and bottom
of a fan shaft, should exceed the area of the shaft
itself by at least 5u per cent.
(di Leading curves at the bottom of the shaft
are a good thing.
(e) The main splits should be as near the
foot of the down-cast pit as possible. Within 100
feet would be good practice.
(f) All air crossings should have cross sections
of 25 per cent, in excess of that of the road delivering
into them, and the grade of approach
should be kept as low as consistent with practical
economy and the volume of air to be passed. This
is also true of an under-cast.
Ig) In all coal mines, where the working zone
is at a distance from the shaft bottom (or drift
mouth) plastered masonry stoppings should be
erected in both main intakes and returns, and
all air scaled to ventilate old workings should be