March 19, 1915.

THE COLLIERY GUARDIAN.

599

r In reply, Mr. Sparks confessed his inability,.owing to
lack of time, to answer all the questions which had been
asked. He said he. had read the paper six times, and
on each occasion ■ the discussion; had been entirely
different, and it was quite an education to have the
subject discussed from so many different points of view.
There was almost unanimity in congratulating him upon
advocating the earthing of the neutral. Only one critic
had taken the opposite view. The measurement, of the
resistance was of great importance, and must be done
carefully, not in a haphazard fashion. Hundreds of
people made earth connections which were valueless,
and he wanted to impress upon them that it was an
important safety point. Some speakers had referred to
the purchase of current from supply companies. In
writing the paper, he restricted himself largely to the
Powell Duffryn works, because it was very representa-
tive, but he was also the adviser to a number of other
collieries which were not so big nor as favourably
situated, and it -appeared to him it was possible in those
cases to get from power companies the moderate
amount required. The cost and working expenses he
had not dealt with, because the paper wras already quite
long enough, and he could not give information which
was more or less confidential, but he agreed that the
members ought to have some comparison, and he W’ould
consider it. The coke ovens were run independently,
and the gas was sold to the electricity department at a
price fixed by arrangement with the colliery manager.
In the South Wales pits there were rats and mice, but
they were never found together. With regard to con-
densers, they started with the surface type, but owing
to the large amount of oil and one thing and another
which came from the winding engine through the low
pressure system into the condensers, the difficulty of
maintaining a good head was very great, and the com-
pany had now adopted jet condensers. From his
experience, he should say that that was absolutely the
right thing to do, though he did not suggest that
surface condensers could not be used.

NORTH STAFFORDSHIRE INSTITUTE
OF MINING AND MECHANICAL
ENGINEERS.

Coal Dust Explosions.

A general meeting of the members of this institute
was held at the Central School of Science and
Technology, Stoke-on-Trent, on Monday evening, when
a paper on “ Coal Dust Explosions ” was read by Mr.
J. B. Morgan. The chair was occupied by the
President, Mr. J. Gregory. An abstract of Mr.
Morgan’s paper appears on p. 593.

In the subsequent discussion, The President said
two new aspects in connection with coal dust explosions
had been put before them by Mr. Morgan. So far as
he was aware, the effect of an excess of coal dust on
the propagation of an explosion had not been fully con-
sidered. He agreed with Mr. Morgan that before any-
thing was finally decided in regard to the use of stone
dust, it would be of the utmost advantage to ascertain
the effect of large excess quantities of coal dust by
means of large scale experiments, such as those carried
out in the Government’s experimental gallery.

Prof. John Cadman, D.Sc., said he had been
privileged to see the small scale apparatus upon which
Mr. Morgan had conducted his experiments, and he
congratulated him upon the ingenuity displayed in the
design. Seeing that so much attention had of late
been given to research upon it, it was surprising
that so little had been accomplished in really discover-
ing the exact limiting conditions under which coal dust
clouds could ignite and be propagated. It was gener-
ally. believed that the Explosions in Mines Committee
had concluded its labours, and that the Sixth Report
was their final one. It was perhaps not unreasonable to
conclude that the committee were satisfied that their
experiments had reached sufficient finality to render
further investigation unnecessary, so far as the intro-
duction of remedial measures was concerned. At the
conclusion of the Sixth Report it was stated that “ 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.”
Referring to the paper, Dr. Cadman said the author’s
suggestion that an increase in the density of a coal
dust cloud might have a diminishing effect upon its
inflammability was open to question, and he would
agree with him that the results obtained in small scale
experiments were not comparable with large scale con-
ditions. The second point was one to which he would
like to lay special stress, as it led to a most serious
question, as to whether the investigation of the problem
was complete, as was now generally supposed. The
author had shown on his small scale apparatus what
had previously been referred to by the Eskmeals Com-
mittee, that the nature of the surface of the tube or
gallery had a very marked effect upon the history of an
explosion. With the conclusion expressed everyone
must agree. To accept, then, the proposals suggested
by the committee as to the quantity of stone dust
necessary to “ very greatly minimise, if not prevent, an
explosion of coal dust,” was a little difficult, seeing that
the experiments which led to the suggested remedy
were conducted in a smooth gallery, particularly when
it had been established beyond question that restric-
tions such as those common to every roadway of a
mine greatly increased the propagating capacity, of a
mixture of coal dust end stone dust when once the same
had become ignited. Indeed, the committee were fully

alive to this fact, and directed serious attention to it;
and the experiments went to show that stone dusting,
so as to produce 50 per cent, ash on incineration, were
capable of materially checking an initial ignition, but
when once set alight it was. not capable of preventing
propagation. It seemed strange, then, that the place
where an initial ignition was more likely to occur,
namely, at the working face, was omitted from the-
committee’s recommendations. One might be misled
into thinking that the Home Office Committee, in their
anxiety to grope at a remedy, started with the fixed
intention of finding stone dust to be a satisfactory and
practicable solution, probably because it was the most
likely looking of all the remedies put forward before the
investigation began. And, in spite of the many objec-
tions to such a dirty and possibly unhealthy material,
and despite the fact that, applied in the manner they
recommend, it was admittedly incapable of stopping an
explosion that had by some unforeseen reason com-
menced at, say, the working face—the most likely place
for such an explosion to commence, and at a place where
it is not suggested that the remedy should be applied—
in spite of these facts, stone dust received the final
blessing of the Committee on the score of its preventing
ignitions. If there were no ignitions, there can be no
explosions. Then, one might ask, why should road-
ways be subjected to the stone dust precaution, for
stone dust could not stop an explosion? Assuming that
every manager was able to foresee eventualities, and
to apply the stone dust remedy to every abnormal con-
dition, whether of coal dust, or accumulation or
outburst of gas, the application of this remedy could be
undertaken with assurance, but in the present state of
our knowledge of the subject, we could surely only
accept the stone dust remedy as a temporary, and not
like some Home Office Regulations, too onerous,
expedient. At the moment there was only one rational
way of viewing this problem, that was, understand the
enemy thoroughly before trying to subjugate him. Find
out, as had not 'been done, the exact limiting conditions
under which coal dust clouds could ignite, and then
seek and apply a remedy which they knew would place
the underground conditions beyond such limits. Such
an investigation might mean years of hard and
laborious research, and it would be a national crime if
the Sixth. Report of the Committee was allowed to
remain the final word of the greatest piece of research
connected with mines ever undertaken by a responsible
Government.

Mr. A. M. Henshaw said with regard to the possi-
bility of an excess of coal dust having a diminishing
effect on the violence and propagation of an explosion,
he was very much inclined to agree with Mr. Morgan.
In investigating one of the largest explosions in the
history of the world, one feature demanded a great deal
of care and investigation, as bearing on this question
of the possibility of an excess of dust having some
neutralising effect. In the case in question, coal was
carried along a level in trams to a staple pit, where, by
means of a tippler, the coal from this upper seam was
tipped and allowed to fall 20 or 30 yds. to the seam
below, where it was loaded into wagons. The coal dust
w’as so excessive—and, of course, very fine—that one’s
feet sank into the dust to the shoe tops. It was, in
fact, heaped up at the sides of the roads to get rid of it.
For some distance along the level the dynamic effect of
the explosion was in evidence, but as they approached
the staple pit it became less and less, and at the top
of the staple there was no evidence of the explosion,
and no evidence that it had gone down the staple to
the seam below. There was, however, evidence of the
explosion in the seam below, though it might have
reached there by some other road. Eventually, it was
held by some of the investigators that the explosion had
travelled through the coal dust to the seam below, but
at the same time they failed to find any evidence of
its having travelled down the staple pit. He had the
impression at the time that the excess of coal dust had
had the effect of stopping the explosion, or, at any rate,
of diminishing its violence. There was also something
to be said in regard to the effect of the surface of the
tube, or the road, on the passage of the explosion.
Everyone who had been engaged in work underground
realised the extraordinary effects that were to be found
—zones giving evidence of the greatest violence,
followed by zones where little violence had occurred,
and yet the explosion had passed those areas to. places
beyond, where.it had again increased in violence. That,
he had long thought, was due to obstructions in the
roads. He had seen stone cruts with even sides where
little damage had been done, whilst places irregular in
character showed evidences of extraordinary violence.
Thus, they had evidence underground corroborating
what had been experienced in the gallery at Eskmeals,
and what Mr. Morgan had discovered with his experi-
ment in a rusty little tube.

Mr. Hugh Johnstone, H.M. inspector of mines, said
one point appeared to be perfectly clear, and that was
that whether or not an excess of coal dust could have
any effect in retarding explosions required to be settled
by experiment. There was room for a great deal more
experiment, but he would strongly recommend that
members should not make the experiment in their
mines by encouraging an excess of coal dust in their
roads.

Mr. Henshaw urged that in using stone dust in mines
they should not be satisfied with one of stone dust to
One of coal dust; they must stone dust in the propor-
tion of two to one or three to one. The work of the
Committee ought not to be discontinued or suspended;
it had a value to the mining community which they
could not over-estimate.

The President said the discussion they had had
clearly showed how debatable the efficacy of the stone
dust remedy really was, in spite of the experimental
work already carried out and the reports that had been
issued. He cordially agreed with Dr. Cadman’s view
that the experiments ought to be continued. He sug-
gested that the discussion should be adjourned to the
next meeting, and in the meantime expressed the
hearty thanks of the institute to Mr. Morgan for his
valuable paper.

Mr. Morgan, in reply, said Dr. Cadman implied that
a 50 per cent, mixture—that w*as to say, one of stone
dust to one of coal dust—would stop an ignition. He
did not think Dr. Cadman quite meant that, because
the Committee’s reports were very inconclusive on that.
There was no doubt that the inflammation in a mixture
of that kind was mot nearly so vigorous as in the case of
pure coal dust, but doubtless they could ignite
a cloud of that mixture; and it did not matter to the
miner whether the flame were rapid or not if there were
200 or 300 ft. of flame going past him. A 50 per cent,
mixture would not stop ignition; it would simply
retard it. It could not be made known too widely
that the work of the Home Office Committee, far from
being final, was scarcely of a preliminary character; it
was purely tentative. The problems to be solved before
any settled knowledge could be established were very
great indeed. He was very glad to have Mr. Henshaw’s
corroboration from actual experience of the two points
he had put forward. To his mind, there was little
doubt about the diminishing effect of an excess of coal
dust upon explosibility.. But it was useless having a
tremendous accumulation of coal dust, and saying,
“ Here is our security,” because the factor that deter-
mined the character of any explosion that might occur
was the state of agitation produced in the air. If the
agitation would not raise any more dust than was
necessary for the explosion, then what was the good of
the excess? Means should be devised to produce the
most violent explosion, in order to see how much dust
could be raised. Then one could proceed to the final
investigation of this question of excess. It was not a
question of so much dust lying on the roadways, but of
how much of that dust could be lifted.

Partnerships Dissolved.—The London Gaztte announces
the dissolution of the following partnerships :—T. H.
Poynter and W. H. G. Edmunds,, under the style of
Edmunds and Poynter, at Buckingham, in the trade of
engineers and cycle dealers; F. H. Powers and C. R. L.
Draycott, ironmongers, cycle dealers, and electrical engi-
neers, at Belwell-lane, Four Oaks, Sutton Coldfield, War-
wick, under the style of Powers and Draycott; C. Worm aid,
C. Ferguson, T. Brook, and J. Scott, turners and machine
and tool .makers, at Calder Vale-road, Wakefield, under the
style of the Yorkshire Press and Tool Company.

Associated Chambers of Commerce.—The president, Sir
Algernon F. Firth, opened the proceedings of the 55th
annual meeting of the Association of Chambers of Com-
merce of the United Kingdom, in London, on Tuesday. - A
resolution was carried approving the action of the executive
council in proposing to the railway companies- that railway
advisory committees should be formed by Chambers of
Commerce in important centres, to negotiate on behalf of
traders and settle with the local representatives of the
railway companies complaints and questions of a local
nature arising from time to time, which do not require con-
sideration by a court of law; and further the proposal to form
a central committee, representing the various local advisory
committees, to negotiate with the general managers, and
settle complaints and questions affecting the trading com-
munity, which cannot be dealt with by the local committees.
Another resolution which was agreed to was that the
Government should be asked to consider the best means of
securing continuity of trade after the war was over, and
the retention of trade gained from Germany and Austria,
which was put in the names of the executive council, Bir-
mingham, and Wolverhampton. There were resolutions in
the names of Leeds, the South of Scotland, and Belfast,
protesting that the proposed scheme of a national company
assisted by Government money to develop the coal tar colour
industry in the United Kingdom would only stifle competi-
tion and establish a monopoly; proposing a substantial
import duty in coal tar colours; and asking the Government
for some satisfactory guarantee against German competition
on the termination of the war, to ensure the adequate estab-
lishment of the manufacture of dyestuffs in this country.
Mr. Bedford (Leeds) said their proposal was that the
Government place a duty of 25 or 30 per cent, on all German
dyes coming into this country for the next 10 years. The
German colour industry had been built up by the very best
chemical research during the last 40 years. The important
side of the question was the chemical one. It was not the
business man, but the scientist, who would really count in
this scheme. Sir Wm. Ramsay had said that British Dyes
Limited, was doomed to failure, because it was not directed
by chemists. It was agreed to divide the Leeds resolution
into two parts, and to vote first of all on the first sentence
down to the word “ monopoly.” Mr. A. Taylor White
(Wakefield) moved as an amendment to this : “ That the
proposed scheme to establish a national company is an
acceptable attempt to solve the question of the deficiency in
the supply of coal tar colours.” This was carried. The
Leeds representatives thereupon withdrew the second part
of the resolution.