482

THE COLLIERY GUARDIAN.

March 9, 1917.

COLLIERY WORKERS AID MINERS’
FEDERATION.

Th© various organised colliery workers outside the
Miners’ Federation of Great Britain are making united
efforts to enforce their claim to individual existence as
separate trade unions, and their rights to recognition in
any national arrangement come to between the Govern-
ment and the workmen’s representatives in connection
with the coal mining industry. Unless such recogni-
tion is conceded, the representatives of the colliery
workers’ trades unions that do not come within the
sphere of the Miners’ Federation, it is contended, cannot
advise the various sections to comply with any arrange-
ments that may be proposed.' The Miners’ Federation,
at the national conference at Southport in 1911, laid
down the principle that all trade union organisations
connected with the mining industry must be merged in
the Miners’ Federation of Great Britain, but it is pointed
out that there are quite a number of separate organisa-
tions, such as the two National Federations of Colliery
Enginemen and Stokers,.the Colliery Tradesmen’s Asso-
ciation, the Colliery Firemen’s Association, the Colliery
Under-Managers’ Association, and other organised
colliery workers, whose wages are regulated by agree-
ments of their own, apart altogether from the Miners’
Federation, and are not directly governed by the National
Conciliation Board. Strong views are held by the repre-
sentatives of these various colliery workers’ trades unions
in regard to the Miners’ Federation leaders dictating to
other unions (which have organised their respective
members and built up agreements for them on account
of their being excluded from National Conciliation Board
agreements) how such unions must be constituted, and,
further, demanding that they must pay tribute to the
Miners’ Federation. It is pointed out that the repre-
sentatives of these separately organised colliery workers,
who have now met in conference to offer their protest,
and affirm their position and rights by specific resolu-
tions, have been absolutely ignored by both the Govern-
ment and the Miners’ Federation of Great Britain in
regard to the formation of the Coal Organisation Board,
absentee conferences, local committees on absenteeism,
and colliery tribunals, notwithstanding the fact that all
their members are affected just as much as those who
belong to the Miners’ Federation, a condition of affairs
which in the emphatic opinion of the unrepresented
organised colliery workers, calls for alteration and
reform. In an interview, Mr. Thomas Watson, secre-
tary of the Lancashire, Cheshire and North Wales
Enginemen and Boil er men’s Federation, who presided
at a conference of delegates at Manchester from no fewer
than 15 separate colliery workers’ trades union organi-
sations, outside the Miners’ Federation, stated that,
without at all wishing to show disrespect to the miners,
it must not be lost sight of that the 90,000 colliery
workers represented at the conference, of which he was
president, are of just as much importance in the work-
ing of collieries as are the whole body of miners repre-
sented by the Miners’ Federation of Great Britain. This
conference, while recognising the great necessity for
some system of closer unity between the Miners’ Federa-
tion and the other organisations representing colliery
workers, could not possibly accept the conditions laid
down by the Miners’ Federation of Great Britain, and
pledged itself to defend the various organisations con-
cerned against any encroachment by the Miners’ Feder-
ation upon their constitutional rights as statutory trade
unionists. Further, it was decided that whatever terms
might be made with the Miners’ Federation, the organi-
sations represented at the conference should insist upon
the right to have complete control of their own trade
union affairs. The representatives at the conference also
claimed, emphasising their claim by resolution, that in
any national arrangement between the Government and
the workmen’s representatives in connection with the
coal mining industry, the colliery organisations repre-
sented at the conference must be recognised as well as
the Miners’ Federation, otherwise they could not, it was
added, advise the various sections to comply with such
arrangement. The Prime Minister, the Home Secretary,
the President of the Board of Trade, and the Minister
of Labour have been notified of the decisions of the
conference.

American Coal in France.—The third instalment, made
public a few days ago, of the report of the American Indus-
trial Commission, sent to France by the American Manu-
facturers’ Export Association, deals with railways and coal,
and states that so far the quantity of coal imported from
the United States has been insignificant. Some of the
French railroad companies have ordered American coal, but
not in large quantities, and some American coal has been
brought over for industrial purposes as well. The possi-
bility of bringing over a large supply of coal from America
hinges chiefly on the freight situation. The present Trans-
atlantic freight rates are practically prohibitive. It would
appear that the outlook for coal shipments from America to
France, during the war, would become really encouraging
only if the Transatlantic freight rate could be reduced to
something like lOdols. per ton for the Atlantic ports, and
about 12 dols. per ton for the Mediterranean ports. The
present prohibitive freight rates in the case of coal imported
from America are due not only to the lack of ships, but also
to the well-known fact that it is difficult to obtain suitable
bulky and heavy return freight from France, because French
exports consist principally of fine goods, frequently of
luxuries of high value in small bulk. There is practically
no anthracite coal produced in France. Anthracite coal is
at present received from Wales, and would be a desirable
product from the United States. The demand for and con-
sumption of anthracite coal is not very great. There is
also a lack in France of gas coal and of coke. There would
seem to be a future for the sale of gas coal, the consumption
of which amounts to several million tons per annum.

EXPLOSIBILITY OF COAL DUST.

In his report on the coal mining work of the United
States Bureau of Mines in 1916, Mr. Van H. Manning
gives particulars of investigations into the following
factors governing the explosibility of coal dust :—(1)
Size of dust particles; (2) quantity of loading, or amount
of dust per unit of area or space; (3) composition of the
coal; (4) effect of wetting coal duist; (5) effect of pre-
sence of inflammable gas on ignition and propagation;
(6) effect of wide rooms or places in starting dust explo-
sions by shots.

Size of Dust Particles.

Tests made originally in the Pittsburg gallery in 1909
and in 1915 in the experimental mine indicated that
particles of dust larger than 20-mesh do not enter into
an explosion except as they may prevent smaller par-
ticles from rising into the air. The coal for these tests
was therefore crushed to a 20-mesh size with either 10,
20, or 40 per cent, to pass through 200-mesh. The
amount of pulverised shale which it is necessary to mix
with these dusts and with pulverised coal dust to pre-
vent the propagation of an explosion started in a 50 ft.
zone of pulverised coal dust, is shown in the following
table :—

Percentage
of shale.

Pulverised coal ............................ 75

20-mesh coal, 40 per cent, through 200-mesh ... .; 70
20-mesh coal, 20 per cent, through 200-mesh. 60

20-mesh coal, 10 per cent, through 200-mesh .. 50

The size of dust which may be present is thus of the
greatest importance; hence in determining the explo-
sion hazard from coai dust in any particular mine, the
size of the dust as well as the quantity per unit of area
found at the face and along the entries back to the
shaft or entrance to the mine is obtained by systematic
sampling of the dusts on the roadway, ribs, roof, and
timbers, and screening tests made of these samples to
determine the quantity of each size of dust particle.

Amount of Dust per Unit of Area of Space.

It was not possible to conduct these tests in the early
stages of the experimental work, owing to the fact that
until more recently the coal ribs were exposed, and there
• was a question as to how far dust from the ribs might
be abraded, and take part in the action. Later, the
portions of the mine in which standard tests were con-
ducted were lined, the floor with concrete and the ribs
and roof with cement mortar placed by a cement gun,
so that all surfaces could be thoroughly cleaned, remov-
ing deyond question the possibility of dust abrading
from the ribs, roof, and floor. The quantity of loading
was varied from | lb. per ft. of entry (0*38 oz. per cu. ft.
of air space) to 61b. per ft. (1-65 oz. per cu. ft. of air
space), these tests being conducted with the standard
Pittsburg dust. Modifications in the figures must be
made for other kinds of coal dust.

It was found that for loadings of 1 lb. per ft. (0*275 oz.
per cu. ft.) of coal dust, and heavier loading, the explo-
sibility is practically constant, but lower percentages of
shale or inert dust are required to prevent propagation
when the loading is less than lib. per ft., and strong
propagation is obtained with pure pulverised Pittsburg
coal dust loaded at the rate of only 0*3 lb. per ft. of
entry (0*83 oz. per cu. ft. of air space). In the Pitts-
burg gallery tests and those conducted by J. Taffanel
in France, ignition was obtained with a smaller quan-
tity, but the quantity named is barely perceptible in an
entry lined with cement, and would be inappreciable in
an ordinary unlined mine passage,

As regards “ super-dusting,” up to 1 lb. per lin. ft. of
entry no lessening of the propagation was obtained. As
61b. per ft. is a very large quantity of dust, such
amounts of dust of a fine character • being rarely found
in mines, it would seem that the possibility of there
being too much coal dust present to propagate an explo-
sion may be left out of practical consideration. It is
expected that in the future further experiments on the
maximum and minimum quantities of dust within a
range liable to be found in commercial mines will be
conducted.

Composition of the Coal.

Many tests were made to determine the percentage of
shale dust that should be mixed with coals of different
chemical composition coming from different parts of the
United States. The results will be reported later, but
in general it may be stated that dusts from coals with
high ash or high moisture content, or dust from coals
approaching anthracite in composition, •require less
admixture of inert dust to render them inexplosive.

Effect of Wetting Coal Dust.

A series of tests were made in the experimental mine
to determine the effect on explosibility of adding water
to mixtures of Pittsburg coal and shale. While, in
general, there was a confirmation of the previous gallery
tests, it was found that in the mine under conditions
wetter than those contained in the gallery propagation
occurred with equally high percentage of moisture, bo
far as the pure dust is concerned. These tests were
conducted in the summer time, and the mine was often
dripping wet. Infone case, it was found that a mixture
of 77 per cent, pulverised coal and 23 per cent, water
(not including the water of composition in the coal) gave
a very strong propagation. The mixtures which would
not propagate for the various sizes of coal are given in
the following table :—

20-mesh coal 20-mesh coal
Pulverised 40 per cent. 20 per cent,
coal. through through
200-mesh.	200-mesh.

Without water...... 25 p c. coal... 30 p.c. coal... 40 p.c. coal.

75 p.c.	shale.	7<'» p.c. shale.	60 p.c. shale.

10per cent, water..	40 p.c.	coal...	40 p.c. coal..	50 p.c. coal.

50 p.c	shale.	50 p.c. shale.	40 p.c. shale

20 per cent, water	........... 80	p.c. coal...	80 p.c. coal.

Effect of Inflammable Gas on Ignition and Propagation.

Tests were conducted with Pittsburg coal dust and
coal dust from various fields upon the effect of inflam-
mable gas (natural gas) in the air current at the time of.
testing. Tests with 1, 2, and 3 per cent, of gas in the
air current were made. It was found that the presence
of gas materially increased the explosibility of coal dust
and mixtures of coal dust, especially of dust approach-
ing anthracite in composition. On an average, it may
bo" stated that 1 per cent, of natural gas will offset 5 to
10 per cent, of shale dust, or other inert dust, in the
mixture; and hence in gaseous mines additional amounts
of inert dust must be added to offset the presence of gas.

Effect of Wide Rooms in Starting Dust Explosions by Shots.

It has always been assumed that dust explosions were
more liable to start in narrow places than in rooms.
With a. view of getting some information on this point,
some tests were conducted in one of a group of adjoin-
ing rooms. This room was 20 ft. wide and 160 ft. long,
and was connected by cross-cuts, or break-throughs, to
the adjacent parallel rooms. A strong ignition resulted
from a blown-out shot, which spread to the adjoining
rooms, and out on to the butt entry, when 20-mesh pure
coal dust was used—20 per cent, of which would pass
through 200-mesh—being scattered on the floor with a
loading of 0*2 lb. per sq. ft. of floor space, vdiich is
equivalent to 0*55 oz. per cu. ft. of air space. The
explosion travelled several hundred feet through the butt
entry, as far as the loading of coal dust extended, but
in another test in which the entry had been freshly
dusted with 61b. of limestone dust per ft. of entry, the
explosion flame was extinguished after travelling along
100 ft. of the entry.

SIGNALLING WITH BARE WIRES.

[Contributed.]

The two Home Office reports and the interest recently
manifested on this subject, recall the discussion which
took place in the columns of the Colliery Guardian,
upon the same subject, over 20 years ago. There had
been a good deal of discussion of the subject in other
quarters, before the South Wales Institute of Engineers
for instance; and the problem involved in igniting mine
gas was not the only one discussed. About that time
there was considerable difficulty with shot firing in
mines, owing to the uncertainty of the behaviour of the
fuses employed, when magneto electric machines were
used to furnish the current. The question of igniting
a detonating mixture, and an explosive mixture of gas
and air, are apparently quite different; but in reality
they are very similar. In both cases a certain quantity
of heat has to be delivered to the mixture, sufficient to
cause combustion; and the question was how could this
heat be provided, and what was the quantity of current,
with varying pressure, and with other conditions
differing. The present writer conducted a large number
of experiments with a view to determining these figures ;
he had not at his command in those days the beautifully
delicate and accurate apparatus that the Home Office
experimenters have employed, and the work which they
have done is therefore a very welcome contribution to
the subject. The measurements which they have made
upon the minimum current required to be passing in an
electric signal circuit, in order that an explosion may
follow when the circuit is opened, are of immense value.
It is always of great service to engineers to have definite
figures to work to; with electrical apparatus especially,
once the working conditions are known, and the figures
representing those conditions, there is rarely any
difficulty in constructing apparatus to meet them. In
the tables accompanying the second report, electrical
engineers who make electrical signal apparatus, have
all the necessary data before them to enable them to
construct and to fix apparatus that should be absolutely
safe under practically all conditions. The electrical
engineers who look after the apparatus at the colliery
also have given to them in the tables referred to, complete
guides that should enable them to maintain the apparatus
perfectly safe. It is well known that an apparatus
when fixed in a coal mine, particularly an electrical
apparatus, is in a far more favourable condition for all
useful purposes than after it has been working for
some time.

The Break Flash between Bare Wires.

The Home Office second report dealt entirely with
the question of the spark, or flash, thaf passes between
the bare signal wires on the mine haulage roads, when
the wires are allowed to fall apart, after a signal has
been given. It will be remembered that the signal on
a mine haulage road consists of two naked galvanised
iron wires, secured to small reel insulators, fixed to
props at the side of the road, and connected to the bell
and battery in the engine house in such a manner that
when connection is made between the iron wires the
circuit is complete and the bell rings. The circuit may
be completed either by bringing the wires themselves
together by the hand or by rubbing another piece of
metal over the two wires. The latter method is a
favourite one, because the wires become dirty and
require to be cleaned before good connection can be
made between them, and rubbing another piece of
metal, such as a file or a piece of wire, over them,
accomplishes this purpose very well. It is the spark,
or flash, which passes between the wires, or between
one wire and the piece of metal that has been used to
connect' them, that forms the subject of the Home
Office investigation. In the writer’s view, however,
though the experiments have been so carefully carried
out, they have not reproduced the conditions existing
on a haulage road in a coal mine, at the point where
the circuit between the wires is opened. The experi-
menters are careful to explain that the method employed
to reproduce the break flash is that given in the