934

THE COLLIERY GUARDIAN

October 30, 1914

We have already explained in our Fifth Report that
samples of mixed dusts collected from the roadways for
the determination of their ash contents should be sieved
through a safety-lamp gauze to exclude large particles.
Any incombustible dust used in order artificially to
raise the ash content of the dust on the roadways,
therefore, should consist so,far as possible of particles
capable of passing through a safety-lamp gauze.

Shales, limestones, and similar substances, which have
been ground so as to pass through a safety lamp gauze,
normally contain a large proportion of much finer dust,
the inclusion of which is of importance. For our
experiments have shown that unless there be present
not much less than 50 per cent, by weight of pai tides
capable of passing through a 200 X 200 sieve, more than
one part of incombustible dust to one part of coal dust
is required to prevent the ignition of the mixture by a
cannon shot.

We have made comparative experiments with the
following materials of different degrees of fineness,
using coal dust of the same degree of fineness in each
experiment (namely, such that the whole passed through
a safety-lamp gauze and about 75 per cent, through a
200 x 200 siev£):—

Percentage by weight
that passed through
Materia .	(---------K--------x

28 x 28	200x200

sieve. sieve.

(1)	Sand ..........................  99	...	4

(2)	AI tofts shale ................. 65	...	18

(3)	Flue dust .................... 90	...	31

(4)	Dolomite dust C‘fine *0....... 68	...	42

(5)	Altofts shale (reground) ..... 98	...	55

(6)	Dolomite dust (“ superfine ”)•••	06	...	66

The materials numbered (5) and (6) on the list were
effective in preventing the propagation of the flame
from a cannon-shot when mixed with the coal dust in

the propoi tion of 1:1. Of either of the materials
numbered (3) and (4), 1^:1 of coal dust was required;
of Altofts shale (No. 2), 2 :1 of coal dust was necessary;
whilst three parts of sand to one of coal dust was not
found to be sufficient.

We are therefore of opinion that care should be taken
that the incombustible dust used for treating the road-
ways should contain not less than 50 per cent, by weight
of fine material capable of passing a 200 x 200 sieve.

The Effect of Diminished Oxygen on the Explosion of Fire-
damp and of Coal Dust.

Proposals have been made to prevent ignitions of fire-
damp in the holds of ships and in mines by mixing the
waste gases from boiler flues with the air so as to
reduce the proportion of the oxygen and increase the
carbonic acid to such a point that firedamp or dust con-
tained in the air was no longer capable of being inflamed,
while at the same time the air should continue to be
safe to breathe for human beings and animals.

We thought it would be of interest to determine to
what extent it was necessary to reduce the oxygen con-
tent in air in order to render methane and coal dust,
respectively, incapable of ignition.

With regard to methane, the results were as follows:—

Per cent.	Lower limit of	Upper limit inflammabili
oxygen	inflammability	
content of	per cent.	per cent.
atmosphere.	of methane.	of methane.
20’9	5’6	14’8
194	5’8	12’9
17’0	5’8	10’5
,	15’8	5’9	8’9
14’8	6T	8’3
13’8	6’4	7’3
13’5	6’5	6’8
13’2	7 No mixture is capable	
and under	) of propagating flame.	

These results show that as the oxygen content of the
atmosphere is reduced, the upper and lower limits of
inflammability gradually come close together. Above
the limit of 13’25 per cent, of oxygen an explosion of
methane in such air is still possible, provided the right
quantity of methane is present to produce it. But
when the proportion of oxygen has been reduced to
17 per cent.—a reduction that is not, we believe,
desirable in air which men and animals have to work in
—any admixture of methane between the limits of
5’8 per cent, and 10’5 per cent, is still explosive.

As regards coal dust, we made a series of experiments
in the spherical explosion bomb already described. It
was found that explosions which developed pressures
amounting to 90 lb. per square inch were readily
obtained from Silkstone coal dust in air containing
19 per cent., 18 per cent., and 17’5 per cent, of oxygen.
No ignition could be obtained under the conditions of
the experiments when the air contained only 17’1 of
oxygen. When, however, the atmosphere also con-
tained 2 per cent, of methane, the oxygen had to be
reduced to 16 per cent, before it became impossible to
ignite the mixture.

Conclusions.

1.	Although the presence of firedamp in the air
facilitates, to some extent, the inflammation of pure
coal dust, we do not think that it diminishes to an
appreciable extent the protective effect of incombustible
dust.

Our experiments, both in the 7 ft. 6 in. and in the
3 ft. galleries, have shown that a 1 : 1 mixture of
incombustible dust and coal du st can be ignited by the
discharge of 24 oz. of blasting powder, and can
propagate the flame throughout the galleries when the
atmosphere contains over 4’6 per cent, of methane but
that 4‘5 per cent, of methane in the air is insufficient to
render the 1:1 mixture ignitible by a cannon shot.

We have also found that a 1 : 1 mixture of in-
combustible dust and coal dust cannot be ignited by the
flame of a fairly violent firedamp explosion.

2.	Our experiments have shown that the wetting of
coal dust in a gallery can be effected best by a fine mist
of water which sinks into and is absorbed by the dust.
Pure coal dust (containing 5 per cent, of ash) required

to be so wetted as to contain 30 per cent, of water
throughout to prevent propagation of flame when 24 oz.
of powder were fired into it. With coal dust wetted in
situ it required an equal weight of water to be used in
the form of fine mist to secure that the large flames
produced (1) by the cannon and 5 lb. of dry coal dust,
and (2) by the explosion of coal gas and air through
150 ft. of the 3 ft. gallery, should not be propagated
through the wet coal dust.

Mixtures of incombustible dust and coal dust may be
rendered less inflammable by water, as shown by the
experiments already described.

3.	Comparative experiments with different incom-
bustible dusts of a mineral character, including powdered
carbonate of calcium and dolomite, show that their
protective action is due mainly to their fineness, and
not to their chemical composition. It is important
that the incombustible dust should contain at least 50
per cent, sufficiently fine to pass through a 200 X 200
sieve.

4.	The experiments that we have made on the reduction
of the oxygen content of the air to so low a figure as
17 per cent., do not support the theories that have been
advanced that such reduction, even if it could be carried
out without detriment to the safety and working capacity
of the miners, would ensure freedom from explosions of
firedamp or of coal dust.

We have now carried our investigations into the causes
and means of prevention of coal dust explosions to the
point at which, in our opinion, it becomes possible for
the Home Office to specify definitely the measures of
precaution which should be taken in mines. ,

The experiments which have been carried on at
Eskmeab during the past three years and the results of
which have been set out in the six reports submitted by
us establish, so far as experiments can, that:—

(i)	The maintenance throughout the roads of such
a proportion of incombustible dust in a state of fine
division as would make a mixture yielding on
incineration at least 50 per cent, of ash ; or

(ii)	The maintenance of at least 30 per cent, of
water in a state of intimate mixture with the dust
throughout the roads ; or

(iii)	A combination of the two previous methods,
i.e., the treatment of the roads first with incombustible
dust and then with water,

would prove effective in very greatly minimising, if not
preventing, explosions of coal dust.

One question remains outstanding, that is the question
of possible danger to the health of the men employed in
the mines from the sprinkling of dust in the roadways.
It is of course essential that no incombustible dust
shall be used for the purpose of mixing with coal
dust, which is likely in any degree to produce
injurious effects, and a provision to that end would
presumably be inserted in any regulations that the
Home Office may make under the Coal Mines Act, 1911.
In our First Report (page 10) we referred to the
question, and, having regard to past experience and to
the results of experiments that had been made, we
expressed the opinion that the dust of argillaceous
shale is innocuous. This is the view held, we believe,
by so great an authority as Dr. Haldane. So many
thousands of men work and have for years worked in
atmospheres more or less charged with shale dust
that had it been in any degree injurious in the
same way as the dust of quartz rocks the results
would have been recognised long ago. It is very
desirable, however, that all possible steps should be
taken to remove any apprehensions on the subject
which may be felt by those who are immediately
affected. Further information, moreover, is wanted as
regards kinds of dust other than shale dust for the
guidance both of owners and of the Home Office. The
question is a physiological one and lies therefore
outside the province of the committee, but we have
with your sanction arranged with Dr. Haldane to
conduct a further special enquiry into the subject,
supplementing the work which has already been done
in the same direction under the direction of the Royal
Commission on Metalliferous Mines and Quarries.
This enquiry has already been commenced, and we
hope that the results will be available shortly.

We very much regret that Prof. Dixon has been
prevented by absence from the country, and Mr.
Blackett by military duties, from considering this
report in its later stages, and that it must be issued
without the support of their great authority. We have
no reason, however, for thinking that they would
dissent from the conclusions reached.

We cannot conclude this report without expressing
an appreciation of the loyal and efficient support we
have obtained from Dr. R. V. Wheeler, D.Sc., and our
staff at Eskmeals ; in this connection we desire to
mention the names of Messrs. T. F. E. Rhead, M.Sc.,
D. T. Jones, M.Sc., M. J. Burgess, A. H. Clarke,
C. B. Platt and A. Hughes.

Henry Cunynghame. R. A. S. Redmayne.

Malcolm Delevingne. A. P.H. Desborough, Cpt

Geological Society of London.—The first meeting of the
session 1914-15 will be held on Wednesday, November 4,
1914, when the following communications will be read :—

The Inferior Oolite and Contiguous Deposits of the
Doulting-Milbourne-Port District (Somerset),” by Mr. Lins-
dall Richardson, F.R.S.E., F.G.S.; “ Some Inferior Oolite
Pectens,” by Messrs. E. Talbot Paris, B.Sc., F.C.S., and
Linsdall Richardson, F.R.S.E., F.G.S.

Immingham Coal Exports. — According to the official
returns for the week ending October 23, the shipments of
coal from Immingham were as follow :—Foreign : Dieppe,
1,251; Gefle, 4,045; Bonne, 1,393; Stockholm, 2,284; and
Svenborg, 701 tons. Coastwise: To London, 2,460; and
Ramsgate, 200 tons; making a total of 9,674 tons foreign,
and 2,660 tons coastwise, compared with 46,917 tons foreign
and 4,550 tons coastwise during the corresponding period
last year.

Notes from the Coalfields.

[Local Correspondence.]

South Wales and Monmouthshire.

Shortage of Labour at Collieries : The Proposed Reduction
of Age Limit for Boys—Tredegar Pits Stopped for Lack
of Men — A Thousand Men Under Notice in Sirhowy
Valley—Pyle and Blaina Works Offered at Auction :
An Extraordinary Record of Finance — Special Police
and Military Guard of Admiralty Pits — New Fuel
Works Adjoining Barry Dock — Cost of Maintaining
Police During Strike—Commission for a Miners' Leader
—Colliery Proprietor's Will.

The Miners’ Federation executive gave consideration last
Friday to the suggestion from the owners’ side of the Con-
ciliation Board that, during the period of the war, it was
advisable that the age at which boys are allowed to work
in the mine should be reduced below 14 years. They
decided that the suggestion could not be approved. Yet the
condition of affairs as to shortage of labour grows more
serious every week. Tens of thousands of men taken from
any single industry would have detrimental consequences,
but the financial effect upon colliery profits is dispropor-
tionately unfavourable, because the large reduction of out-
put—whilst standing charges, expenses of upkeep, remain
unrelieved — must inevitably operate very adversely upon
the net balance. It will in some cases even turn profit into
loss, notwithstanding high prices. It is notorious that the
added relative charges of recent years—due to legislation, to
reduced output per man, lessened hours, higher prices of
stores and material, and other causes—have put the profit
per ton upon a less unsatisfactory level; and, therefore,
unless heavy output be available to compensate, a grave
condition may arise in certain instances.

As yet no proposal has been made to suspend the Eight
Hours Act, though the idea is privately mooted, and is
likely to come into open discussion, seeing the effect which
the new law has had in reducing the income of quite a
large proportion of the men. Original complaints have died
down, but the loss of earnings is said to be none the less
keenly felt.

The Tredegar Company have issued notice terminating
contracts to 700 men in their employ at Tredegar, and to
250 in the house coal seam at Oakdale. The reason
assigned is that owing to the number of recruits who have
left the collieries, there are not sufficient men remaining to
work them at a profit. Other collieries have been similarly
affected; and (according to Exchange observation) report a
shortage of labour due to the heavy recruiting. Moreover,
the labour difficulty is becoming more intense because of the
fact that recruiting, although diminished, shows no signs of
being limited.- Indeed, if the crucial question of adequate
provision for wives and other dependants can be disposed
of, there is no question that a huge impetus will be given to
enlistment.

The Tredegar colliers held a mass meeting on Friday last,
when their agent, Mr. A. Onions (treasurer of the Federa-
tion), submitted his report upon an interview with the com-
pany’s representatives in relation to the notices tendered.
The deputation was assured that the whole of the colliers
under notice would be able to find employment in the other
pits; but that assurance did not apply to day wage men.
Another reason was the high percentage of small coal that
was filled in the pits, small coal at the present time being
a drug in the market. The deputation were informed also
that unless there were considerable improvement two other
pits would also be stopped ultimately. Mr. Onions reported
that an interview had been arranged with Mr. Tallis, the
general manager. There was a probability also of 100 men
in the Waterloo level being served with notices; and alto-
gether about 1,000 men were under notice in the Sirhowy.
One of the speakers at the meeting suggested that the action
had been taken in order to force young men to join the
Army; but Mr. Onions said that the deputation were
assured that such an idea was absolutely unfounded. The
meeting decided to make a strong appeal to the Tredegar
Company that the notices should be withdrawn pending the
completion of arrangements, so that the men could gradu-
ally find new places.

Two collieries in the Avon Valley district have been
closed during the past month owing to the war; and at the
local Federation meeting on Saturday last the miners’
agent (Mr. Jenkins) reported that there was no prospect
of early re-opening, but he added that steps were being
taken to secure employment for the men at other collieries,
and that the railway companies had been asked to afford
facilities for their conveyance. Mr. Jenkins stated that he
had approached the divisional insurance officer with regard
to miners employed on public works, in order to get exemp-
tion from paying the unemployment contributions under the
Act.

The Pyle and Blaina Works at Blaina, in Monmouthshire,
were offered for auction last wTeek, and the attempted sale
aroused unusual interest because of the extraordinary finan-
cial experiences of the undertaking during recent years. A
complete collapse succeeded a huge dividend distribution, the
consequence being that a received entered into possession,
and a sale was ordered by the Court. In addition to the
blastfurnaces specially constructed for ferro-manganese and
spiegeleisen, there is a complete coal washery and about 160
coke ovens, with other manufacturing plant; and the works
were offered as a whole, the site comprising an area of 54
acres. The company paid 12 per cent, in 1906, and in the
following year no less than 20 per cent, dividend, with 33|
per cent, bonus in shares or cash, making 53J per cent,
altogether. As a result, the T1 shares ran up to over 48s.
quotation on Cardiff Stock Exchange. Then financial diffi-
culty arose, and nothing has been paid since; indeed, within
two years a heavy debit balance was reported. An attempt
to raise money by debentures failed, and in 1910 a receiver
was appointed, and the shares quotation ran down to Is. 6d.
At the auction no bid was made, and offers privately were
invited.

The Chief Constable of Glamorgan reported in Tuesday
to the Standing Joint Committee that arrangements with
the military authorities for guarding the Admiralty area
of the South Wales coalfield had worked satisfactorily, the
National Reserve, of late attached to the Welsh Regiment,
having been detailed for service locally.

Tn the course of his speech at the meeting of Baldwins
Limited, the chairman, Col. Wright, stated that the number
of men who had joined the Colours from their works was