996

THE COLLIERY GUARDIAN

May 17, 1918.

porous than the rest. Two other slides represented
vertical and horizontal sections of the seam. They
showed the large resinous bodies contained in the coal.
When the coal was broken up into dust-like particles
the edges of those bodies were revealed. The vertical
section contained layers of leaves which showed the
tissue almost perfect. Another section showed the
leaf laminae parallel to the bedding of the coal. The
section was taken right through the length of the leaf.
From these sections, considering the texture of the
coal, the fineness of the dust, and so on, one could
easily see that if by some chance or other there had
been an accumulation of gas, dust of that sort would
be likely to cause a violent explosion. A more com-
plete investigation of the material would be of great
interest.

Mr. Files said his experience of outbursts of gas
tended to show that boring in advance would be of
service. He happened to be down a pit one day when
a sinker was boring a hole. Suddenly the drill was
blown out of his hand and carried ten yards away.
The pressure of gas that came from that particular
bore hole was certainly tremendous, though it was
only a small seam.

At the close of the meeting the slides prepared by
Mr. Lomax were shown by the lantern, operated by
Mr. Atherton, and further explanations were given
by Mr. Lomax.

Mr. Siddall remarked that he was indebted to Mr.
Lomax and to Mr. Atherton for the additional interest
they had given to the paper.

NEW MAXIMUM PRICES FOR
FRENCH COALS.

The French Minister of Munitions has issued the
following additional list* of maximum prices for the
various collieries mentioned. The figures in paren-
theses immediately preceding the prices relate to the
average maximum percentage of ash content in the
coals.

Soc. des Mines du Bourbonnais (Commentry).

Provisional Prices.—Through and through picked,
over 20 mm. (25 per cent.), 50 fr.; small, 0-20 mm.
(45), 20 fr.; through and through (40), 25 fr.; wash-
ing sludge (50), 18 fr.

Definite Prices when the Commentry washery begins
work, and not later than August 1, 1918.—Large
picked coal, over 55 mm. (20), 62 fr.; washed nuts,
20-25 mm. (20), 62 fr.; washed small, 0-20 mm. (24),
52 fr.; through and through (40), 25 fr.; re washed
schists (50), 18 fr.; sludge (50), 18 fr. (all at pit head
or washery).

Cie. Fermiere de l’Etablissement Thermal de Vichy
(Mine de Megecoste).

Through and through picked, over 20 mm. (25),
50 fr.; small, 0-20 mm. (40), 30 fr.; through and
through (35), 35 fr.

Soc. des Houilleres de Saint-Chamond.

Coal with 15-17 per cent, volatiles.—Nuts, over
25 mm. (16), 49 fr.; through and through (20), 44 fr.

Soc. des Mines de Janon-Terrenoire.

Through and through (1), Saint-Felix (25), 50 fr.;
(2) Avaise (25-35), 44 fr.; (3) Avaise (35-45), 37 fr.

Cie. des Mines d’Anthracite de la Mure.

Anthracite with 6-8 per cent, volatiles.—Large
broken and screened, 55-80 mm. (16), 52 fr.; eggs,
35-55 mm. (16), 53 fr.; nuts, 25-35 mm. (16), 53 fr.;
broken and screened, 25-55 mm. (16), 48 fr.; screened,
over 15 mm. (18), 41 fr.; small (1), 14-25 mm. (18),
44 fr.; (2) 6-14 mm. (22), 36 fr.; (3) 3*5-6 mm. (22),

31	fr.; (4) 25-3*5 mm. (22), 28 fr.; crushed slaty
coal, 4-23 mm. (35), 30 fr.; fine slack, 0-5 mm. (35),
25 fr.; briquettes (25), 51 fr.

Cie. des Houilleres d’Ahun.

Lean anthracite coal with 10-12 per cent, of
volatiles.—Large (1), over 40 mm. (18), 54 fr.; (2)
over 40 mm. (18-30), 42 fr.; cubes, 30-80 mm. (25),

54	fr.; washed nuts, 15-30 mm. (36), 31 fr.; washed
smithy small, 0-15 mm. (25), 48 fr. Briquettes.—
Blocks (24), 64 fr.; ovoids (24), 62 fr.

Soc. des Houilleres de Bosmoreau.

Anthracite with 8-10 per cent, of volatiles.—Through
and through special, over 16 mm. (28), 45 fr. Ovoid
briquettes (25), 61 fr.

Soc. de Commentry-Fourchambault et DecazeVILLE
(Mine de Brassac).

Lean anthracite coal with 10-12 per cent, of
volatiles.—Large, over 50 mm. (13), 52 fr.; small
cobbles, 60-80 mm. (13), 53*50 fr.; washed cubes,
25-60 mm. (15), 55 fr.; washed nuts, 12-25 mm. (15),
48*50 fr.; washed beans, 6-12 mm. (12), 44 fr. Ovoid
briquettes (18), 66 fr.

Soc. des Charbonnages du Centre (Mine du
Charbonnier).

Anthracite with 8-10 per cent, of volatiles.—
Screened cubes, 55-80 mm. (15), 64 fr.; washed nuts,
25-55 mm. (15), 64 fr.; washed nuts, 15-25 mm. (15),

55	fr.; washed small, 5-15 mm. (15), 48 fr.; unscreened
small, 0-5 mm. (20), 30 fr. Washery sludge (25), 20 fr.
Ovoid briquettes (18), 66 fr.

Soc. des Huilleres de Messeix.

Anthracite with 6-10 per cent, of volatiles.—Large
screened, over 60 mm. (16), 55 fr.; washed nuts,
30-60 mm. (12), 61 fr.; 16-30 mm. (12), 51*50 fr.;
6-15 mm. (12), 42 fr.; washed small, 0-10 mm. (14),

32	fr.; unwashed small, 0-16 mm. (20), 25 fr.
Washery sludge (22), 20 fr. Ovoid briquettes (18),
61 fr.

* See Colliery Guardian, May 10, 1918, p. 943.

Soc. des Houilleres de la Haute-Loire (Mines de
la Taupe et de Grosmenil).

Large, over 50 mm. (12), 58 fr.; through and
through screened, over 40 mm. (12), 53 fr.; washed
nuts, 18-40 mm. (12), 56 fr.; washed smithy nuts,
over 18 mm. (10), 50 fr.; nuts, 18-40 mm. (18), 42 fr. ;
washed smithy small, 10-18 mm. (10), 46 fr. Washery
sludge (20), 20 fr. Briquettes (12), 64 fr.

Houilleres de Marsanges.

Through and through regraded, over 15 mm. (18),
49 fr.; washed grains, 10-15 mm. (16), 44 fr.; washed
slack, 0-10 mm. (16), 38 50 fr. Washery sludge (22),
25 fr.

Soc. des Mines de Champagnac.

Large, over 40 mm. (16), 47 fr. ; washed nuts,
35-60 mm. (22), 47 fr.; small washed nuts, 25-35 mm.
(22), 47 fr.; washed beans, 14-25 mm. (22), 47 fr.;
washed grains, 9-14 mm. (18), 43 fr. ; through and
through, free from dust, over 5 mm. (18), 41 fr.
Briquettes (16), 64 fr.

Soc. des Mines de la Bouble.

Large (1), over 60 mm. (12), 47 fr.; (2) over 60 mm.
(12-18), 42 fr.; screened, over 15 mm. (15), 42 fr. ;
screened nuts, 20-60 mm. (16), 40 fr. ; washed nuts,
30-60 mm. (14), 45 fr.; washed beans, 15-60 mm. (14),
41 fr.; washed gas small, 6-15 mm. (14), 38 fr. ; washed
gas slack, 0-15 mm. (12), 35 fr.; washed steam small,
0-30 mm. (16), 33 fr.; unwashed small, 0-15 mm. (20),
30 fr.; through and through re-graded, 0-15 mm. (15),
39 fr. ; through and through picked, 0-60 mm. (16),
38 fr. Briquettes (14), 58 fr.

Schneider et Cie. (Mine de Decize).

Large, over 42 mm. (15), 47 fr.; cubes, 28-42 mm.

(15)	, 46 fr.; nuts, 15-28 mm. (15), 43 fr.; washed
small (1), 0-15 mm. (15), 38 fr.; small (2), 0-15 mm.
(15-25), 25 fr. Washery sludge (27), 20 fr.

Cie. des Mines de Bourbon-Saint-Hilaire.

Flaming coal.—Large (1), over 55 mm. (25), 44 fr.;
(2) over 55 mm. (25-40), 25 fr.; nuts (1), 32-55 mm.

(25)	, 42 fr.; (2) 32-55 mm. (25-30), 34 fr.; small nuts

(1)	, 18-32 mm. (26), 36 fr.; (2) 18-32 mm. (26-35),
28 fr.; beans (1), 10-18 mm. (26), 30 fr.; (2)
10-18 mm. (26-35), 24 fr.; washed small (1), 0-10 mm.
(28), 25 fr.; (2) 0-10 mm. (28-40), 20 fr. ; through
and through, free from dust, over 10 mm. (20), 34 fr.

Soc. Nouvelle de la Condemine (Mines des
Plamores).

Flaming coal.—Large (1), 60-100 mm. (28), 42 fr.;

(2)	60-100 mm. (28-35), 27 fr.; nuts (1), 10-65 mm.

(26)	, 40 fr.; (2) 10-65 mm. (26-32), 32 fr.; cobbles,
110-130 mm. (30), 30 fr.; small, 0-10 mm. (30), 24 fr.;
through and through (35), 22 fr.

Mine de Buxieres et la Courolle.

Flaming coal.—Large (1), over 60 mm. (28), 42 fr.;
(2) over 60 mm. (28-40), 25 fr.; nuts (1), 30-60 mm.
(26), 41 fr.; (2) 30-60 mm. (26-32), 35 fr.; small nuts,
15-30 mm. (30), 30 fr.; small, 0-15 mm. (37), 20 fr.

Cie. des Mines de Houille de Bert et de
Montnombreaux.

Flaming coal.—Large (1), over 60 mm. (18), 42 fr.;
(2) over 60 mm. (18-31), 33 fr.; nuts (1), 25-60 mm.
(20), 38 fr.; (2) 25-60 mm. (20-33), 30 fr.; beans,
0-25 mm. (30), 28 fr.; small, 0-8 mm. (30), 22 fr.
Ovoid briquettes (28), 50 fr.

Cie. des Quatres Mines Reunies de Graissessac.

Large, over 250 mm. (15), 46 fr.; 100-250 mm. (15),
44 fr.; cobbles, 45-80 mm. (17), 43 fr.; Bousquet
screened, 30-200 mm. (19), 39 fr.; Bousquet works
coal, 15-150 mm. (25) 33 fr.; nuts, 30-45 mm. (20),
38 fr.; gas nuts, 10-28 mm. (12), 45 fr.; smithy,
10-28 mm. (12), 45 fr.; washed small, 0-28 mm. (15),
37 fr.; through and through (1) (20), 33 fr.; (2) (15)
41 fr.; re-washed small, 30-45 mm. (40), 27 fr.
Washery waste (60-65), 7 fr., (50) 10 fr.; sludge (25),
18 fr. Briquettes.—Blocks (15), 64 fr.; ovoids (25),
57 fr.

Cie. des Forges de Chatillon, Commentry, Neuves-
Maisons.

Large (1), over 60 mm. (14), 51 fr.; (2) over 60 mm.
(14-20), 44 fr.; (3) over 60 mm. (20-27), 37 fr. ; through
and through re-graded (19), 44 fr.; through and
through, Noyant-Ferrieres (15), 45 fr.; through and
through, Saint-Eloy, 0-60 mm., 38 fr.; nuts (1),
Noyant-Ferrieres, 30-60 mm. (13), 50 fr.; (2) 30-60 mm.
(13-17), 46 fr.; (1) Saint-Eloy, 30-60 mm. (17) 46 fr.;
(2) 30-60 mm. (17-21), 42 fr.; small nuts, Noyant-
Ferrieres, 18-30 mm. (20), 46 fr.; Saint>Eloy,
18-30 mm. (20), 43 fr.; washed small (1), 0-18 mm.

(16)	, 36 fr.; (2) 0-18 mm. (16-25), 31 fr.; unwashed
small, Saint-Eloy, 0-18 mm. (25), 31 fr.; Ferrieres,
0-18 mm. (16), 36 fr. Washing sludge (28), 20 fr.
Briquettes (18), 59 fr.

Determining Carbon Content in Furnace Fuel.—The
estimation of the total carbon in fuels is a highly
important factor in the study of economical heating, and
affords the only means of establishing the heat balance
of a furnace, and other useful details, such as the sum
total of heat utilised or lost. D amour and de la Moriniere
describe an apparatus for this purpose, consisting of a
combination of the Mahler-Goutal bomb with the usual
absorbent tubes. A capsule of quartz containing 0-5 grm.
of the test fuel is placed in the apparatus. After the
explosion, the gases are passed through the absorbents,
increased weight of the tubes indicating the carbon content
in an hour and a half. Corrections have to be made for
checking the small amount of carbon dioxide left in the
bomb. The authors also describe steam tests on a boiler
series. The full carbon content of the fuel and the
determination of the calorific power were the factors
employed for gauging the losses per kilogramme of coal
consumed through joints and cracks in the flues and
chimney. By this method, possibility of saving 16-5 per
cent, in the fuel consumption was demonstrated. Tests
on an open-hearth furnace also showed that a saving of
between 15 and 20 per cent, can be effected with a
neutral or slightly reducing atmosphere.

STONE DUSTING IN MINES.*

By A. Rushton.

The question of stone dusting in mines has been
given serious thought and consideration by mining
officials for some considerable time past. It has also
engaged the attention of the Home Office to such an
extent that it was legislated upon in the last Mines
Bill, and stone dusting was made compulsory in dry
and dusty mines. The object of stone dusting is, of
course, to counteract the coal dust which is always
present in the deep, dry and dusty mines now being
worked in the Lancashire coalfield. When those
mines were being opened out the disasters which
occurred at various pits varied so much in character
that the experts, as a result of their investigations,
were led to believe that some powerful agent besides
gas was at work which caused such loss of life and
destruction to the mines and property. A series of
experiments were carried out, and the country is
indebted to Sir Henry Hall, I.S.O.—who for many
years was inspector of mines for the South-West Lan-
cashire district—for his research work and the results
obtained by him about 20 years ago. In conducting
his experiments, Sir Henry used an old pit shaft at
the White Moss Colliery, Skelmersdale, and by his
experiments with different qualities of coal from col-
lieries in various districts, he proved conclusively that
coal dust, and coal dust alone, could cause a serious
explosion. That having been definitely proved, the
responsibility rests with colliery owners and mine
officials to reduce the risk of explosions by removing
the coal dust or counteracting its evil influence in
the mines.

Roads and Dust Deposition.

In the author’s opinion, the size, shape, and con-
struction of mine roads has a great bearing on the
subject because of the weight of dust which can be
deposited in them, both visible and invisible. For
instance, a main roadway which is bricked by a semi-
circular arch is the best and safest of all roadways,
and it will contain less hidden coal dust than any
other road. Another safe type of roadway is one
with sufficient thickness of ripping, taken down from
the roof, to bury the coal sides or packs along the
road sides, the roof and sides being properly squared
up and the road fairly free from timber. The roads
which collect the most hidden coal dust, and nurse
it, are strait places driven in the coal where, after
a time, the coal fractures and breaks along the sides,
causing crevices and openings to be formed, and also
packed roads in wide work, which suffer little through
subsidence, * and are lined or built up on each side
with stones from either the roof or floor and heavily
timbered with bars for roof support. As the coal
dust is carried along in the air current it is deposited
in the crevices, etc., which are fairly numerous and
possess an extensive dust-collecting surface. If steel
girders are used for roof supports the gathering ground
for the dust is very much increased. When such a
road is being retimbered a dense cloud of dust can be
noticed when the old-standing timber and packs are
being disturbed.

On the question of prevention, the author considers
that water is the best antidote to coal dust in mines,
and where water zones can be made it is a very safe
and comforting friend to the colliery manager.. But
as it is impossible to use water in most mines, the
next best method to be adopted is that of stone dusting,
which was proved to be an effective antidote to coal
dust by the experiments carried out, about ten years
ago, by Sir W. E. Garforth at his experimental
station at Altofts Colliery, Normanton. There are
various systems of stone dusting in practice—the best,
in the author’s opinion, being that of using an ejector
or dust sprayer. The dust, by means of compressed
air, is blown through the sprayer into the atmosphere
of the mine, and being in suspension in the air
current it is carried along and deposited on the roof,
sides, and floor and in the crevices practically in the
same manner as the coal dust is deposited.

Sprayer.

The sprayer is made principally of wrought iron
tubing, 2 in. inside diameter and about 20 in. in
length, with an UL” leg of about 10 in. The
straight length of pipe is reduced at one end to three-
quarters of an inch diameter to admit the compressed
air. The UL” leg is inserted into the dust, which
is then sucked up and blown out at the other end of
the straight pipe, this end being belled out to expand
the dust cloud. In order to use the sprayer the mine
must be provided with compressed air, which is now
extensively used, in deep mines, for coal cutting. If
the compressed air is already at hand it is only neces-
sary to lay the pipes along the road selected and
make the connections wherever desirable. By way of
illustration, we may take a main intake haulage road,
2,000 yards long, 10 ft. wide, 6 ft. high, and passing
an air current of 50,000 cu. ft. per minute, which has
not already been provided with compressed air pipes.
A 2 in. range of pipes could be laid and connections
made every 300 yards along the road. During the
day the dust could be sent in 2 cwt. bags or boxes to
each connection, so that when the operator starts
stone dusting he will empty the bags on the floor or
board provided, connect the sprayer to the compressed
air, insert the “L” leg into the stone dust, and with
40 lbs. pressure of compressed air in ten minutes he
will have blown the dust away, disconnected the
sprayer, and be ready to travel to the next connection.
Allowing ten minutes for the operator to reach the
next connection and be ready for operating, 900 yards
of roadway can be stone dusted in an hour. On that
basis an operator could cover the 2,000 yards of road-
way and get back to his starting point well within
three hours.

Omitting the capital charge for pipes, the cost of
the sprayer and the operation is very small indeed.
The sprayer has practically no upkeep charges, and
the cost for wages is low, as the work can be done

* Paper read before the Manchester Geological and
Mining Society on Tuesday, May 14.