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THE COLLIERY GUARDIAN.

June 28, 1918.

logged and soft, but when it was dried it was per-
fectly good, and it took a beautiful polish, showing
that it had not decayed. More knowledge was re-
quired about the conditions which produced decaying
wood. It seemed to him that there were natural
antiseptic substances in the wood, and that those had
to be got rid of in some way or other before the wood
was capable of decaying, and that for it to decay not
only was oxygen required, but also moisture, as shown
by Mr. Graham’s experiments. When one got well-
exposed wood which had probably lost all its anti-
septic substances, it would begin either to oxidise or
to form methane—in other words, to ferment. He
had tried fresh sawdust, and had watched a big heap
of sawdust for a year or two up in Scotland. He
had taken the temperatures in one of the heaps of
sawdust and watched it, but for about a year there
was no sign of heating. After another year or so
it began to get warm; it was evidently oxidised. The
next year it seemed to be hotter still, and no doubt,
if kept long enough, probably all the antiseptic,
resinous substances would be washed out of the wood
or destroyed in some way, or bacteria might exist
and raise the temperature, and then the wood would
heat just like hay. Mr. Graham seemed to have got
both the chemical oxidation and the bacterial oxida-
tion with the old wood. Those shales were from an
old pit, he thought, and had probably lost their anti-
septic substances in the process of standing in the
pit. With reference to the main points in the paper,
the origin of blackdamp had been a puzzle to him
for many years, but he thought that now Mr. Graham
had probably got the truth on the point. It amounted
to this, that in a pit which was damp, and where
the air was more or less damp and the timber was
rotting at a great rate, one got a lot of CO2 in the
blackdamp, whereas in a dry pit the timber was too
dry to rot at any speed, and most of the blackdamp
was nearly pure nitrogen. There were cases in metal-
liferous mines where C02 was given off from carbonates
by sulphuric acid. There were therefore several
different causes, all due to one form or another of
oxidation; but the oxidation of timber was perhaps
the most serious thing, because it meant the destruc-
tion of that timber. If it were possible to prevent
that, it would be an important point in mining.
Carbon monoxide was still another mystery. It rather
looked as if carbon monoxide was formed in all sorts
of oxidations, but it also disappeared. He had known
cases where it had disappeared mysteriously in gas mix-
tures. For instance, if one kept a sample of coal gas
over water for some time, it was unstable and dis-
appeared in some way, and he thought there were two
processes—a formation process and a disappearing pro-
cess. But that was a matter which must be decided by
further experiments. A number of mysterious cases
of carbon monoxide trouble had occurred among the
coal trimmers in a coal bunker, the men trimming
the cargo of coal being knocked over owing to the
formation of carbon monoxide.

Mr. D. M. Mowat said he would like to ask Dr.
Haldane one question, viz., whether the wood cap in
the Cumberland iron ore was similar in any way to
the conditions as to quantity of wood in an ordinary
coal waste. He took it that the wood was added to
under the existing old timbers, and that in time there
came to be a great mass of wood.

Dr. Haldane said that was so—a great mass of
decaying wood. One could realise it at once if one
considered how one of those ore masses was worked
by the subsidence method. It was the same method
as was used in Kimberley in the diamond mines.
They found a big mass of haematite, and then they
sank shafts in the limestone at points where the
shafts were safe and would stand, and then they
worked into the mass of haematite, taking it off layer
by layer from the top. The ground above simply sub-
sided, and if looked at from above it resembled an
old quarry about 200 or 300 years old. They took
out the first layer of haematite, and they had the
timber, of course, to keep up all the overlying mud
and stuff. They left all that timber, and it crushed
in and the mud came down. Then they took the
layer below, and left the timber again before they
started on to another layer, and so on. The conse-
quence was there was a layer of old, decaying timber
with earth and mud on the top of it following them.
It constantly tended to increase in so far as it did
not decay. If one went into the top workings, it
was sometimes hot quite close to the surface, the
temperature there being perhaps 49 degs., whilst
50 ft. down the temperature was perhaps 90 or 100
degs. close in amongst the timber. It had to be ex-
posed at every fresh layer of work, and got more or
less dry, and after a time, if one let air into it,
it produced blackdamp, whilst if the air were kept
out it produced firedamp.

The President said that Dr. Haldane had referred
to the number of tons of timber which were oxidised
per day in the airways, etc., of a mine as calculated
from the analysis of the return air, and he thought
it would be of interest if a precise illustration of the
method of calculation could be given, so that some of
the members who were not so familiar with chemical
reactions could work out the calculation for them-
selves.

Mr. Ivon Graham said that one way of calculating
was this. If one assumed that all the carbon monoxide
coming up the upcast shaft was produced from the
decomposition of timber, then, knowing the air
current, supposing one had a current of 100,000 cu. ft.
per minute coming up and one found 0-2 per cent,
of CO2 in the upcast, that would give 200 cu. ft.
of carbon dioxide per minute; 44 grammes of carbon
dioxide would contain 12 grammes of carbon. In
a given quantity of carbon dioxide one could calcu-
late the actual amount of carbon that was coming
up the upcast, and, assuming the blackdamp was from
the decay of timber, that carbon had come from
the timber itself. Then Mr. Winmill took the timber
as being cellulose, containing about 60 per cent, of
carbon, and from that he calculated the amount of
timber which had been consumed. It came to some-

thing enormous. He (the speaker) did not know the
exact amount of timber that was present in a big
mine, but he should think it was very considerable.
As a matter of fact, he had worked it out himself in
another way. If one got several thousand tons of
timber gradually decaying, the upcast air would con-
tain about 0'2 per cent, of carbon dioxide, with a
velocity of about 100,000 cu. ft. per minute. One could
get that result on the assumption that one had several
thousand tons of timber underground. Replying to
Dr. Haldane, Mr. Graham said that the rate of decay
came out to several tons per day. In some laboratory
experiments on the rate of oxidation of an old piece
of wood showing fungoid growth, he found it was
oxidising practically at the same rate as fresh coal.
Before expressing much opinion on that, however, he
would prefer to do a good many more experiments;
it was not to be decided in a short time.

Firedamp v. Blackdamp.

Mr. D. M. Mowat thought they were very much
indebted to Mr. Graham for the paper before them
and for the series of papers. He did not agree with
any view which sought to reduce the value of such
papers. One never knew where such investigations
would lead. It had struck him while Dr. Haldane was
speaking of the time which elapsed before the saw-
dust began to heat, that that possibly had some re-
semblance to the results which were mentioned in
the last paper by Mr. Graham on “ The Oxidisable
Constituents of Coal.” There, by solution of pyridine
or chloroform, or perhaps both, coal was separated into
two parts, or perhaps more—two parts at any rate—
one which Mr. Graham called the resinous, and the
other the residue. In reading that paper he thought
that the results were perfectly consistent with what
one would expect, because whilst no doubt the
resinous part had some relation to its name, and was
a part which was distinctly inflammable, and there-
fore oxidisable at a certain temperature, it was not
a substance which was oxidisable at a normal tempera-
ture, because, as they had always understood, it con-
tained the antiseptic and preservative part of a body,
the resinous part. It looked to him as if the heap
of sawdust required a solution of pyridine or chloro-
form to dissolve out the resinous part, and then the
residue which remained, the oxidisable part, was
attacked, and that the action in the sawdust was
clearly what one might expect from the results given
by Mr. Graham in his paper on the oxidisable con-
stituents. They had not the same keen interest in
chokedamp to-day as they once had, thanks to the
greater quantity of firedamp. He thought the miner
was more indebted to firedamp than anybody would
give firedamp credit for. When pits were shallow,
in the old days which Mr. Gerrard had spoken of,
and there was practically no firedamp coming off, the
pits were full of blackdamp, and the reason was that
the wood, lamps and coal were there, and there was
no ventilation. In spite of attempts at legislation,
progress was slow until firedamp appeared in greater
quantity and it became impossible to go on without
having more ventilation. When that took place, the
greater amount of ventilation swept away the black-
damp till it had become to a great extent a thing
of the past. He knew a case in one of his own mines
where, also in the good old days, a large area was
left in a seam, with small pillars which they hoped
some day to take out. It was 8 yds. square, and
with rooms perhaps 10 ft. wide. That was the best,
the most sensitive, barometer he knew, because there
was a great issue of blackdamp from that waste. A
waste like that was to some extent a sealed waste—
sealed to the extent that it was impossible to get
into it. It had fallen, but it had not crushed together
like a longwall waste, and therefore it was a gasometer
—a good reservoir of gas which was not accessible.
From a waste like that there were large issues of
blackdamp. But in the last twenty years he had
never seen much trouble arise from the exudation of
blackdamp from the longwall waste; he had never
known it to cause much more than temporary in-
convenience. As to the small percentage of carbon
monoxide, he was surprised, on hearing the paper,
to find that carbon monoxide was given off as a con-
stituent. He had not known that that was the case.
It might account for some deaths, although probably
Dr. Haldane would say that the cases where a person
had gone into the waste and been overcome and lost
his life were more likely to be due to want of oxygen
than to the presence of a small percentage of carbon
monoxide. In Table 1, in the second column, in the
analysis of return air, the carbon dioxide percentages
were given at different times from the commencement
of the experiment. After 21 hours the percentage of
carbon dioxide was 0-24, and it went up to 0-42. He
understood that that was not cumulative, but that
it was the actual analysis of the return air. (Mr.
Graham assented.)

Direct Oxidation.

Prof. L. T. O’Shea said there were only one or two
points to which he would like to draw attention.
First of all, what was really meant by blackdamp?
He assumed that they might take blackdamp to be
a residual gas consisting of nitrogen and carbon
dioxide which had been brought about in some way
in a pit by disturbing the ordinary numerical relation
between oxygen and nitrogen in the air, in conse-
quence of which one got a gas, blackdamp, which
was of most varied composition. Th question of the
carbon monoxide seemed to him to I >f considerable
importance. He and many others had a suspicion that
carbon monoxide was a product of the direct oxidation
of coal, and must have been in existence in the atmo-
sphere of old workings at least, although perhaps they
had not obtained in many cases direct evidence of it.
The results which Mr. Graham had obtained seemed
to him to confirm the view that it was produced by
the direct oxidation of the coal rather than y the
vegetable growth of the fungi, because where the
moist wood treated with zinc-chloride and blackdamp
formed in small quantities, presumably by oxidation
alone, Mr. Graham found carbon monoxide, whereas

without such treatment Mr. Graham got no carbon
monoxide at all; and he gathered from what Dr.
Haldane and Mr. Graham had said that in the second
case the carbon monoxide was probably due to the
growth of some organism. It was startling to learn
the large amount of oxidation that went on in the
wood, and how very largely that was responsible for
the presence of blackdamp in the pits. He trusted
that investigations of that kind would be continued
at Doncaster, and that they might have some further
contributions from Mr. Graham, or from that labora-
tory, in the future.

Dr. Haldane said they were greatly indebted to
Mr. William Smith, of the Dalmellington Coal and
Iron Company, for the help he had given over the
experiments. Mr. Smith had suggested several addi-
tional experiments, which he hoped would be done at
some time in one of his pits later on, but was a little
sceptical as to whether there was enough timber left
in the old workings and places where the blackdamp
came from to produce all that oxidation. That could
be decided by crucial experiments made underground.
One would much sooner trust experiments of that
sort than experiments on a small scale in a laboratory,
since unless the conditions underground were known,
they might be overlooked in laboratory experiments.

The President said that the quantity of timber used
in the mines had a bearing on the question. They
used anything from 1 to 3 tons of timber for every
100 tons of coal raised, probably an average of 2 tons
(taking Scotland as a whole). If one knew the coal
extracted from any particular pit, that would give,
roughly, the amount of timber that was left lying
in it. The subject of the decay of timber was put
forward two or three years ago by the institution as
one of the next subjects that should be tackled in the
way of research, and probably if it had not been for
the war that subject would have been brought forward
and gone into by a committee of the institution. He
hoped that before this time next year they would
have made some arrangements by which such re-
searches could be financed, in addition to the Doncaster
Laboratory, to enable research of that kind to be
carried on more freely. He would like the members
to record a very hearty vote of thanks to Mr. Graham
for his most excellent paper, and he proposed that it
should be kept open for discussion at the next
meeting.	.

The vote of thanks was carried by acclamation.

Mr. J. Ivon Graham, in reply, said, in reference
to Prof. Groom’s remarks, from the laboratory ex-
periments he found a very small quantity of com-
bustible gas in the nature of methane or hydrogen
produced. It was very small compared with the black-
damp produced. Of course, different bacteria were
responsible for the production of the gas, and he might
not have had the special bacteria in the samples of
wood examined. On the question of the production
of carbon monoxide he quite agreed with Dr. Haldane,
and he thought there was a good deal to be found out
about that. He, too, had had some bother about the
carbon monoxide. At one time it practically dis-
appeared—that was, the quantities were not the same
as one would expect from such an experiment.
Judging from experiments, the blackdamp from coal
should contain a large amount of carbon monoxide.
He thought he was right in saying that the physio-
logical effect would be due to the deficiency of oxygen
before one got the effect of carbon monoxide. The
point about the timber was very interesting. He was
quite unaware of the exact quantity of timber being
used; it seemed to be tremendous, so that one could
understand that in a damp pit it was quite possible
to obtain all the blackdamp from the decay of timber.

Flow of Air through Small Coal.

A paper was read on “ The Flow of Air through
Small Coal and other Broken Material,” * by Mr.
J. T. Storrow, chemist at Brodsworth Colliery.

Discussion.

The President said that this was another paper
recording careful laboratory experiments, giving data
as to the flow of air under varying conditions.

M^\ D. M. Mowat said that as the member who
had raised the question at the last meeting about
the rate of flow of air, he would say that they were
indebted to the author for the trouble he had taken
to answer the question. He had not read the paper
until he had heard it read, and therefore could not say
very much about it. He noticed in a general sort of
way that it was only when one went below the % in.
size that one departed from the square root ratio.
In the | in. size, for instance, the figures in practice
were almost identical with the actual experimental
figures, but when one got to the one-tenth in. size
there began to be a marked departure; the quantity
was somewhere between direct proportion and the
proportion of the square root of the pressure. When
one came to one-thirtieth in., which was fairly close,
the proportion came to be direct, as Dr. Haldane had
suggested a year ago in connection with that matter.
There was no doubt that the goaf back from the face
at some distance would be closer than the latter
figures, but within a considerable distance of the face
he could imagine many fissures wider than one-tenth
in. and not limited to one-tenth by one-tenth. The
interstices there were not interstices in the same way
as they were between granular particles, but were
mere slits liaving a measurable width and considerable
length. Whether that would have the effect of re-
ducing the flow in exactly the same way he did not
know. He did not know whether the writer had
formed any theory to account for the change which
took place—why the resistance in the form of larger
particles should not interfere with the ordinary
accepted law of the resistance to the passage of gases—
and when one came down to the very fine size, some-
thing occurred there evidently to modify the relation-
ship between pressure and volume. The figures were
certainly very conclusive.

* See Colliery Guardian, June 14, 1918, p. 1198.