1170

THE COLLIERY GUARDIAN.

June 22, 1917.

areas of coal lying unworked because of that. He
believed, from his own experience of it, that the only
practical solution was hydraulic stowing, and one
colliery had started it where they were worldng a seam
immediately under the foreshore. On the sea side
they had sunk a bore from the foreshore to the coal
works, and poured down sand and water from the fore-
shore. f Fortunately, the foreshore belonged to the pro-
prietor of the. minerals, otherwise possibly it would
not have been practicable. It was going on to-day
with a certain degree of success. But if one was
taking out 1,000 tons of coal per day, a good deal of
sand was required to fill the,gob, and one had to put
in even a still greater quantity of water, which had to
be pumped up. Hydraulic stowing appeared to be
the only cure they knew of, but it was a cure which
could only be used in certain circumstances, otherwise
the cost became commercially prohibitive. He would
be very glad if any member could throw any light on
the working of seams of that kind without having to
revert to hydraulic stowing.

Col. W. C. Blackett (Durham) asked Dr. Haldane
what would be the effect if one put sea water down
instead of fresh water.

Dr. J. S. Haldane (Oxford) did not see that there
would be any harm in it.

Col. Blackett asked if there would be any good
in it.

Dr. Haldane did not know of any good which could
arise from it, except that sea water stopped ankylo-
stomiasis. It was proof against that. But then they
had no ankylostomiasis.

Mr. E. 0. Forster Brown (London) quite appre-
ciated the fact that Dr. Haldane did not want to
commit himself to more than he cared to, but kept to
actual results as far as possible. He would be very
interested to know whether the investigations, and
those of Mr. Winmill, into the causes of spontaneous
combustion had in any way narrowed the limits within
which that cause existed. The author had mentioned
South Wales steam and anthracite coal: he thought it
was correct to say that the mass of the coal in that
'field was lower in volatile than the coal in the other
important coal fields in this country; and, so far as the
best steam coal was concerned, he thought it was also
lower in ash. Fie was particularly interested in the
subject, because he was associated with some develop-
ments in practically a new field, where virtually
nothing was known about the actual future working
conditions. While there were limited analyses avail-
able from boreholes, there was very little information
as to what one actually had to meet when shafts were
sunk deep .enough. In that connection, he would also
like to ask whether there were facilities for having
coal from that particular coal field tested at the pre-
sent experimental station at Doncaster.

Mr. T. F. Winmill (New Whittington, Chester-
field) desired to associate himself with the tribute paid
to Sir Arthur Markham and Mr. Fryar. He had
worked in their laboratory for a long time, and he
wished to say how thoroughly Dr. Haldane and he
appreciated all their kindness to them,- in fact, the
laboratory could not have existed without their
sympathy and initiative. There were other members
more qualified to pay more eloquent tributes to them,
so that perhaps he might confine himself to some points
on which he knew more than some of the other mem-
bers. Dr. Haldane had adopted the uniform principle
from the beginning of insisting that whatever results
Mr. Graham and he (Mr. Winmill) obtained should be
published under their own names. Members of the
institution would, of course, know quite clearly that
the success of the laboratory work had been due to Dr.
Haldane’s clear foresight and encouragement. As
explained by Dr. Haldane, the experiments sounded
very simple, but as soon as one began to make experi-
ments on such a complex substance as coal one got
into difficulties at once. There was no definite sub-
stance to serve as the starting point, and to which all
the measurements could be referred. Coal and its
reactions and so on were so complex that it needed an
exceedingly clear head and logical mind to guide one
through the mazes; and. had it not been for Dr.
Haldane, the experiments would very soon have got
into a tangle that could not have been unravelled.

Mr. J. Ivon Graham (Bentley Colliery) wished to
associate himself with the remarks which had been
made by Mr. Winmill.

Mr. D. M. Mowat (Coatbridge) wished to make one
or two remarks on the paper. Dr. Haldane had
pointed out the fact that coal was practically imper-
vious to the passage of oxygen, or largely so. Of
course, he did not suppose Dr. Haldane suggested that
while coal might be in that condition, the coal seam
was also in the same condition. The coal seam was
cut up by what were called in Scotland “backs and
cracks,” which gave access to the interior of the mass
of coal to a very considerable extent, without bringing
the outside atmosphere into very close contact with
the interior of the cubical- pieces forming the coal
itself. He wanted to draw attention to the fact that
the coal itself might be very dense, but the coal seam
might be comparatively porous. For instance, he had
seen a case where a coal seam was struck in a mine, at
a depth of 250 fms., and the water came through freely
from the beginning, although the coal itself was hard
and dense. It was merely the distinction between a
piece of coal and a seam of coal that he wanted to
draw attention to. There was one other question that
he wished to ask Dr. Haldane. Pyrites had been very
often blamed as the primary cause of underground
fires. He wondered if the presence of pyrites caused
a more rapid disintegration of the coal, so that the
presence of pyrites might be the primary cause of the
tire through the coal being broken down. They had a
seam in Scotland where the lower portion of the coal in
certain areas had never been known to fire, or practi-
cally never. . The portion above that, 3 ft. thick or
thereabouts, was very liable to spontaneous combus-
tion. Thirty years ago the upper part was always left
unworked as inferior coal; it contained a consider-

able portion of pyrites, and a much higher percentage
of sulphur. After having heard Dr. Haldane read
the paper, he wondered whether it was a mechanical
cause or something brought about in the same way as
the swelling of lime shales through the presence of
water—whether the presence of pyrites produced a
more rapid disintegration of coal, which would lead
to the heating of the coal itself. Dr. Haldane had
said that the flow of air through broken coal or other
porous material varied directly as the pressure and
not as the square root of the pressure. By broken coal
he assumed that Dr. Haldane meant coal which was
found in a coal bing where the air spaces were between
pieces of coal. It was not suggested that the air in
that case was passing through the coal itself, but
through pieces of coal. In making fan tests, he had
several times produced an artificial resistance to take
the place of Murgue’s equivalent orifice. Fie was
wondering, after reading the paper, whether the result
got from such a trial could in any way give a wrong
result, because that resistance so induced was very
much like the resistance caused by the passage of air
through a mass of stones or broken coal. He was sur-
prised to learn that the pressure varied as the quan-
tity and not as the quantity squared, as in the case of
resistance to the passage of gases through orifices or
tubes.

The President said that two other papers were
simultaneously open to discussion, along with that of
Dr. Haldane, viz., “ The Permeability of Coal to Air
or Gas, and the Solubilities of Different Gases in
Coal,” and “The Absorption of Oxygen by Coal—
Part X. : The Formation of Water in the Oxidation
of Coal,” both by Mr. J. Ivon Graham.

Mr. J. Drummond Paton (Manchester) said that
while he had not been able to confine his investiga-
tions to coal, he had been forced to investigate the
stability of alloys. In connection with the intrusion
of another element, such as pyrites, in a body such as
coal, he had considered the intrusion of other elements
in metallic alloys. There was a phase which he did
not think was considered sufficiently in its chemical
aspect. If there was any rise in temperature in a
compound in which there were two materials, one had
what was known as the Chatelier effect, which was
known to investigators, though perhaps not so well
known among mining engineers. Chatelier effects in
metals were, to his mind, the determining factor with
regard to the stability of the material. Therefore, he
would suggest that there should be an investigation on
that basis into the combination of pyrites with coal.
If one took a pure copper wire and heated it, and con-
nected the ends across a galvanometer, no current
passed; but if one combined with it a certain amount
of some other element, such as zinc of a higher posi-
tive relation or a lower negative, there was a distinct
electro-thermic effect, and the stability was deter-
mined by the magnitude of that effect. It was well
known that a simple element was more or less stable,
but the moment one introduced a compound one pro-
duced instability; and instability was a function of
the balance of those currents he had mentioned. If a
10 per cent, platinum-iridium wire and a 2 per cent,
platinum-erbium wire were joined and used as a
thermo-couple, and submitted to certain critical heats,
one would get a transfusion of the iridium from the
10 per cent, wire into the 2 per cent. wire. One had,
therefore, an unstable condition, and he held that
pyrites and similar elements in coal could produce a
segregation of an element which—though it might not
be immediately attacked by oxygen while in the com-
pound known as coal—did become more liable to attack
on that basis.

Mr. R. W. Dron (Glasgow) said there was one pro-
blem passing through his mind on which investigation
might throw some light. Practically, he was very
often up against the difficulty of knowing when to
leave well alone. For instance, a few weeks ago he
had been asked down a mine to see the point where
heat was commencing in the gob. After considering
all the circumstances, against the advice of the men
on the spot, which was to start in and dig it out, he
said, “ Leave well alone.” The result up to the pre-
sent time had been perfectly satisfactory. They let
well alone, and allowed the face to proceed; the
affected portion became buried in the gob, air was
entirely excluded, and the temperature had gradually
died down. As far as he could see, the danger was
past. That was one practical point on which, as prac-
tical men, they were getting enlightenment from the
experiments which were being carried on. It really
came to be a critical question whether one was to start
and dig out a gob-fire, or was to let it alone and let
it die a natural death. Another point on which he
thought further investigations were required was the
point mentioned in the paper of the extraordinary
solubility of gas and liquid in coal and other solids. The
point Col. Blackett mentioned with regard to further
investigations as to the effect on other solids such as
shales which were associated with the coal, might be
one of the lines of investigation. For instance, in old
wastes, especially old wastes near the surface, they
were continually troubled by the occurrence of black-
damp. Was that blackdamp given off by the broken
materials in the wastes ; and, if not, what was the
cause of its liberation? Probably, investigations on
those lines would help them in their practical difficul-
ties of knowing how to deal day by day with those gob-
fires as they occurred.

Col. W. C. Blackett said that Dr. Haldane would
forgive him for reminding him of the fact that, in the
worst seams in the North of England which gave off
blackdamp, free sulphuric acid was present in large
quantities; in fact, in some cases they had found it
impossible to pump the water with ordinary pumps
because they were eaten away. He thought that the
effect of sulphuric acid upon the substances in a mine
ought to be remembered.

Mr. T. F. Winmill said he had seen the place to
which Col. Blackett referred. So far as one could see,
free sulphuric acid was always the result of the oxida-

tion of pyrites. In the particular place referred to
by Col. Blackett, there was plenty of pyrites which
was oxidising, and which afterwards fired, and there
was plenty of sulphuric acid, also ferrous sulphate,
calcium sulphate, and magnesium sulphate. He had
never heard of any place where one got free sulphuric
acid in which pyrites was not oxidising.

The President said it was understood that Dr.
Haldane’s paper and the two papers by Mr. J. Ivon
Graham, which were attached to it, would remain open
for discussion at the Newcastle meeting in September.
He hoped that the members who were unable to attend
would send in written communications.

Dr. Haldane’s Reply.

Dr. J. S. Haldane, in reply, said that, first of all,
he would like, on behalf of the Doncaster Coal Owners’
Committee and the companies who supported the
Doncaster laboratory, and on behalf of the staff of the
Doncaster laboratory, to acknowledge the very kind
resolution which had been passed and the kind words
which had been said about the work of the laboratory.
His only regret was that the two men who started the
laboratory were no longer present among them to
know of the resolution which had been passed. A
great many points had been raised, and a great many
questions had been asked which he was quite unable to
answer or to throw any light upon. First of all, with
regard to Col. Blackett’s questions and the fact which
he had brought forward, that gentleman’s experience
with the heap of old waste stuff was certainly very
interesting. He supposed that the new heap had just
slightly warmed the old heap, and got it up to a tem-
perature where oxidation started again. All the
oxidisable material which had been waiting there for
30 years, but had never got to the temperature at
which it would oxidise, just started. He supposed
that was the probable explanation. With regard to
the source of carbon dioxide in mines, Mr. Winmill
had made a number of oxidation experiments on
shales, and it appeared that they would not give off
any carbon dioxide. They had been very puzzled by
the absence of carbon dioxide in oxidisation experi-
ments. Of course, sulphuric acid was a beautiful
agent for liberating carbon dioxide, but it was absent
both at Doncaster and in many mines. The theory
he had advocated 10 years ago was that sulphuric acid
liberated carbon dioxide from carbonates, and thus
accounted for the carbon dioxide of blackdamp ; and
certainly that was the case. He had seen places again,
for instance, in Cornish mines, where there was no
timber about and no coal and nothing to oxidise except
iron pyrites. There one found huge quantities of
calcium sulphate formed by the action of the sulphuric
acid; and one saw that action still going on. One
went into a place like that, and one’s lamp went out,
and the place was as hot as a furnace. There was clearly
nothing else there to oxidise but iron pyrites, and it
did oxidise. No doubt that was the case in coal mines
to a certain extent also. It was that which impressed
him first of all in the North Staffordshire mines. His
first experiences in mining were, he thought, in the
Bullhurst seam. That was a well-known seam in
North Staffordshire for firing. There the old coal
could be seen broken up by crystals of sulphate of iron,
which was simply crumbled to pieces into powder.
He thought it was Mr. Mowat who had raised the
question whether the disintegration caused by the
pyrites increased the oxidation of the coal. Well, it
would; but then the worst of that theory was that
oxygen must already be present in order to oxidise the
pyrites, and disintegrate the coal. The iron pyrites
could not swell up and form crystals of iron pyrites
and disintegrate the, coal until the oxygen was already
there. That was the only difficulty about that theory.
The disintegration of coal by pyrites, when it occurred,
as it did, in the Bullhurst seam and in the Earl seam,
which Mr. Mowat mentioned, was a very striking
thing. Col. Blackett’s remarks more or less related to
those of Mr. Mowat. Col. Blackett asked about the
jelly-like material which was found. He had hoped
that Col. Blackett was going to talk about a very
interesting organism, which had been found in an Ayr-
shire mine. He smelt sulphuretted hydrogen while
going along the mine, and Mr. Winmill and he picked
up some gelatinous material which was sticking to the
stones, etc/, in water flowing out of an old working.
On examining that gelatinous material at Doncaster,
they found that it was an organism which had the
unpleasant property of producing sulphuretted
hydrogen. When it was left in the bottle and kept in
a fairly warm place it produced a tremendously strong
effect, and the smell nearly knocked one over. It
seemed to live on calcium sulphate, which it converted
into sulphuretted hydrogen; and if one fed it occa-
sionally on a little calcium sulphate it needed no
oxygen. Many of those growths in mines were no
doubt very important, especially the organisms which
attack timber. It was possible, of course, that most
of the blackdamp ordinarily came from the decompo-
sition of timber; and in the hamiatite mines, where
there was a huge deposit of decomposing timber on
the top of the works where the surface was let down,
there was not only a tremendous formation of black-
damp, but also a considerable evolution of heat. He
had seen a temperature of 90 degs. within 50 ft. of the
surface in a haematite mine. It was about as hot a
place as one could meet with anywhere underground.
It might be that the decomposition of timber had more
to do. with the formation of blackdamp than ha?
hitherto been assumed. He himself had always blamec
the coal for the formation of blackdamp. That was
one of the questions which would have to be settled in
the future by further observation and experiment.
Mr. Mitton had spoken of the variability of a seam
within a short distance, and that was a very remark-
able thing; one had seen it before. It was certainly
so at the Bullhurst seam in North Staffordshire, which
in some places simply could not be worked, because if
entered anywhere it fired. A short distance further
on it could be worked apparently in comparative
safety. Mr. Mitton’s case was perfectly similar to
that. No doubt a chemical examination of the coal