316

THE COLLIERY GUARDIAN.

FbBKUAKY 6, 1911.

shire it was necessary and he encouraged the managers
to report every case. In North Staffordshire the gobs
as a rule were full of gas, whereas in South Staffordshire
they were not. In the Black Country there were scores
of fires loaded out which never gave rise to serious
trouble, but in North Staffordshire the loading out was
a very different thing. If all these slight heatings were
reported to the inspector, it must follow that they must
either all be investigated, or he must use his discretion
as to how far his staff can undertake the work. If they
were to follow up all the slight heatings in South
Staffordshire the whole staff would be occupied on
nothing else. But, on the other hand, if it was left to
the inspector on the reports of gob fires that were sent
to him, he might in some cases overlook what might be
a very serious fire. He was not prepared without a good
deal of thought to suggest a regulation. Regulations
were rather dangerous things to frame, and one did not
like to commit oneself to exact phraseology.

Asked whether he would approve of a regulation being
made that all the gassy and dusty mines should be stone-
dusted, witness said he thought that would be rather too
drastic. In many of them shotfiring was not permitted,
or only permitted under very strict regulations, and to
require the whole mine to be stonedusted would be
drastic. Many of them ran for years without a gob
fire. In some few cases they were stonedusting
systematically, but he could not say it was general
throughout the district. Personally, he would rather
welcome a rule requiring stonedusting over every dry
and dusty mine road. He was only thinking of the
objection the owners might consider; but even from
their point of view a regulation that there should be a
zone of not less than 120 yards in every direction round
the fire should be adopted. As to the nature of
indications that should dictatestonedusting, he did not
think the matter could be dealt with by merely taking
thermometer readings, because it occasionally happened
that accumulations of rubbish containing carbonaceous
matter heated without being on fire. Therefore, one
would require to have some definition of what was the
smallest indication bf fire, and witness could not quite
see how any regulation could be framed which would
require a manager to report every indication of fire.
The question of temperature presented another difficulty.
They might have a very wide range of normal tempera-
ture in a mine. In mines in North Staffordshire one
part of the mine was perhaps 70 degs., and another
part of it would go up to 90 degs. A standard of
120 degs. would not be unreasonable so far as tempera-
ture was concerned, but it would be unreasonable in
another way. Take two cases—one in a bord-and-pillar
working at Hamstead, for instance. It frequently
occurs there that a very slight gob stink is detected.
There is no apparent heat; but they cut ifito the coal at
a point whence the gob stink seems to issue 1 ft., or it
may be 3 ft., in the coal, and get a crack running
parallel with the road, and that crack is full of live fire,
red hot; but there is no indication of increase of
temperature outside. In the rule as framed, the
manager would have to report it as soon as they got
the fire, but he would neglect to report it altogether
simply from the indication of gob stink. Then, again,
take the case of longwall working where there was a fire
in a pack. If it is near the intake roadway, the
temperature in the roadway may rise. On the other
hand, they may redd through the pack for 3 or 4 yards
and get a live fire; but in this case the temperature in
the roadway may afford no indication that a fire is
there. Mr. Rigby suggested the words “ fire, or
grounds to suspect a fire by reason of gob stink, or
otherwise,” and which witness thought would pretty
well cover it.

Withdrawal of Workmen.

With regard to withdrawing men, witness said that if
a general regulation were laid down that no men were
to be permitted to enter a mine where a fire had been
stopped off or was being filled out, that would practically
mean the closing of the North Staffordshire district and
the whole of the Black Country. In North Staffordshire
witness thought there was more danger present to-day
in the working of the mines than there had been in past
years. In past years gob fires were chiefly in the more
highly inclined seams, and the practice was adopted in
those highly inclined seams of flooding the gob with gas.
In a very inclined seam that was a comparatively safe
proceeding ; but now they were working under practi-
cally the same method in seams much less highly
inclined. In a thick seam with an inclination such as
at Jammage, a seam 20 ft. thick, rising at the seat of
explosion about 1 in 5, it followed that they had a zone
in their broken work stretching from the working face
back for a distance of possibly at least 50 ft. which was
not open to inspection, which was overlaid by gas, and
in which a gob fire might develop at any moment.
There was no possible means of getting in to inspect
it either for gas or for gob fires. The gob stink
from such a fire might rise into the gob behind. The
smell might not come out into the accessible portion.
The higher temperature, owing to the greater, depth,
added to that danger to some extent. During the
process of stopping off, so far as witness’s experience
had gone, the men were stopped in the whole of the pit.
In some cases there was very little open gob; in other
cases there was a great deal of open gob; and if there
was any reason to believe that that open gob was left
charged with gas, he would certainly deprecate the men
working in any part, unless it was stonedusted, until
the stoppings had been put in and had been there, say,
a week. If the roads had been stonedusted in such a
way as to render the propagation of a coaldust explosion
impossible, he should say no. In most cases he should
prefer the immediate introduction of stoppings, and
withdraw the men altogether without wasting time over
stone-dusting. In some cases the time the stonedusting
would take would produce an explosion. That was why,

as an inspector, he would welcome a regulation that all
roads should be systematically stonedusted. In some
mines it would be a hardship—in old mines where the
roads were already of enormous length, and where the
area of coal to be exhausted was comparatively limited.
In North Staffordshire the coal might be worked in
advance, but the whole of the seam was not taken out
in the thicker seams. It was ripped down in the road-
ways ; but very often in some of the seams there was
3 to 4 feet of coal left on above the packs. That came
down in the wastes and was got out as far as they could,
but there was a very large quantity of carbonaceous
matter, coal or coal shale, left in the gob.

Continuous Working.

Answering Sir Arthur Markham, witness said con-
tinuous working was an important factor, because even
settlement tended to prevent excessive falls of roof in
certain parts of the goaf. But so far as fires were con-
cerned, his experience in Scotland was that the chief
danger of irregular working was that the roof cut along
the coal face and closed there. In the Dysart seam, to
which Mr. Robinson referred, there was coal left on the
roof, and if the faces were allowed to stand the roof cut
along the face, sat down, and a lot of coal was buried,
and that almost invariably got on fire unless it was got
out at once before it fired. In many cases it could not
be got out readily, and they cut in at the gate end and
won it afresh, leaving in many cases a thin rib of coal
between the fall and the new cutting. That thin rib of
coal crushed under the roof weight and very often fired ;
but the fires from irregular working occurred much
more frequently at the face, or in the neighbourhood of
the face, than back-bye in the gob. The settlement of
the roof tended to consolidate the gob ; a fresh gob
would not fire so readily as a gob which was probably
some months old. If the face was kept constantly
advancing the settlement of the roof tightened the gob
and prevented the air leaking through it before it got
old enough to oxidise sufficiently to get on fire. If, on
the other hand, the face was stopped for any consider-
able time, they had a certain zone there—a strip along
the face—where the gob is not sufficiently solid to
prevent air getting in through it, and that was where it
fired. There was sufficient air going through to oxidise
the coal and fire it, but not sufficient to carry away the
heat that was generated. He was now speaking
entirely of flat mines. The very same thing applied to
the deep and shallow coals in South Staffordshire. If
the face was allowed to stand for any long period they
very often had fires breaking out, and nearly always
within a short distance of the face. Where they have a
liability to gob fires, as a rule, during a strike they had
men constantly travelling through the pit watching for
any indication of a gob fire and dealing with it as it
arose. The most likely case he knew of for gob fires to
break out quickly was Hamstead. There during the
miners’ strike, oddly enough, they had rather below
than above their average of gob fires. But it was very
injudicious to rest one’s opinions upon a single case.
At Hamstead their method of working was entirely
different to that which obtained in other places. In
some of the works they prepared for the eventuality of
fires by closing up and putting stoppings. In a seam
which is liable to gob fires the seam ought to be so laid
out and so worked that stoppings can be put in readily;
otherwise the system is defective.

The Dangers of Gob Fires.

In answer to Mr. Smith, witness said that he thought
they would find, if they analysed the figures, that
almost all those killed in North Staffordshire had really
been killed by explosions following upon gob fires. In
South Staffordshire the risk was that of poisoning from
the gases because of incomplete combustion. There was
very little risk of explosion there. Mr. Johnstone said
he did not know any cases in his district where reporting
would have improved matters. Witness said it was
very difficult to define the normal state of temperature
in a mine. In a large mine he should like to see the
temperature kept below 80 degs. But in certain parts
of some North Staffordshire mines the temperature was
constantly a good bit above 80, and up to 90 and 92 had
been actually tested, and 92 was normal in that mine or
in that part of the mine, whereas in another part of the
same mine the normal temperature was 75. That was
a mine 900 yards deep.

Replying to Mr. Smith, witness said the period in
which a place through standing would become dangerous,
depended very largely upon the depth of the workings,
to some extent upon inclination, and to a greater extent
still upon the nature of the roof. Some places would
close in a week; others might stand open for three
months. Taking the case in which an inspector saw
fire coming from a pack, witness said that if he had any
means of knowing that the explosion, such as it was,
was due to the ignition of a small accumulation in a
comparatively small cavity—a flash of light through a
pack 20 yards thick would not alarm him much if there
was no gas or dust in the air which was coming from
where that flash was coming out. But, on the other
hand, if be had no means of knowing the condition of
the gob, if it were against a fault where there might be
a very large cavity, the roof having fallen out, he would
certainly not have the men working there if there were
a flame flashing through the pack. Of course, there
are many pits which are continually giving off gas, but
in which the percentage of gas in the travelling airway
never approaches the ignition point. If he saw, in any
mine that he had any connection with as inspector or
manager, a flame flashing through the pack into an
air-course carrying 4 per cent, of gas, he would have
every man out of that pit as fast as he could.

Mr. Johnstone said that where there was no gas and
no dust, or, in other words, where there was no risk of
explosion, he would content himself with taking means
to prevent leakage of air from the gob passing the men
on the return side. It would depend very largely on

the nature of the atmosphere that was coming off. He
had seen gob-fires dealt with where the atmosphere
coming off was quite breathable on account of the fresh
air coming in. In other cases it was so offensive that
men could not work there without using an apparatus.
As to the extent of stonedusting witness said if the
seam in which the explosion originated was isolated by
a long cross-measure drift, and that crut was wet, then
he would not require the dusting of the non-gassy and
non-dusty seam, because he would depend on the crut
arresting any explosion that might occur in the dusty
seam.

Flashes through the Pack.

With.reference to the point raised in regard to flame
coming through the pack, and the dilution of the gas,
witness said he thought the highest percentage of gas
he had encountered under such circumstances was 17.
If it had got to 2, he would have asked for the
workmen to be withdrawn. Of course, the Coal Mines
Act required 2J. He was referring to where the gas
in the gob was igniting, and the air being practically
clear there was no vitiated air going on to the fire. So
that the fire was leaking into practically an innocent
and innocuous atmosphere, and there were no cavities.
He did not explain to Mr. Smith, as he ought to have
done, with regard to this case, that not only was that
gob packed tight, but between that gob and the next
gate, 40 yards on the other side, there was also a tight
gob; there was no waste.

Reducing Temperature.

Sir Arthur Markham interrogated witness on the
subject of temperature. He said if the natural tem-
perature of the strata was 92 degs., he would reduce that
temperature by passing large volumes of wind through
the mine. If there was a large volume of air passing
along the gateway in a mine, and that volume of air was
passing sufficiently slowly to allow it to take up heat
from the strata, it would heat up the air to the tempera-
ture of the strata. But if, on the other hand, the air-
course was not sufficiently long and the air was not kept
sufficiently long in contact with the strata, it would not
heat up to that point, and as it robbed the strata of its
heat, the temperature of the air would be less rapidly
affected.

. Sir Arthur said he had had some experiments made
on this question, and found after the air had travelled a
thousand yards into a mine they could pass what
volumes they liked, but the temperature of the air came
up to the normal temperature of the mine. The experi-
ments extended over five or six years, and there was
gradual cooling. They found the greater variation
with a strong roof and where it used to stand up for a
very considerable distance. Then when they had heavy
waste, the heat in the working place for a time was very
high. Witness observed that if the roof stood up they
would have a very large area and consequently a very
low velocity, whereas, if the roof came down, they would
have an enormous crushing of the coal and therefore a
very rapid oxidation. He did not know which would
account for the quick rise in temperature at the face.
It was, in his opinion, practicable for the normal
temperature of the mine at the working face, which was
92 degs., to be reduced by ventilation. It would not be
cooled down, perhaps, very rapidly, but as the cold air
was continuing for a long period to blow through it, it
would gradually rob the strata of its natural heat and
cooled it down. That would not take place in the working
places in the mine where they were stripping a new face
all the time. If they carried the cold air they gradually
cool the main intake to a point constantly extending
inwards. Then on the actual working face they were
constantly exposing a fresh surface, and the cooling
again would not be so manifest. But as the face
advanced, the extent of the cooled airway would extend
proportionately. It was a problem that was causing a
great deal of attention now among mining engineers as
to what should be done with the deeper workings,
because their workings now were nothing like so deep
as they probably would be 20 years hence. It was a very
serious problem, and he did not see how it was going to
be dealt with otherwise than by improved ventilation.
In a large open area, the velocity of the air was very
low and its cooling effect was very little. The physio-
logical fact was perfectly well known that if the air was
moving, although not at all of a cool temperature, it
had a cooling effect. The cooling effect of the air upon
the body was simply due to the evaporation of the
perspiration on the body. If the air was moving, that
evaporation went on more rapidly, and they had a sense
of coolness, though the thermometer would tell them
it was not 1 deg. cooler. Now the more rapidly the air
was moving along the working face, the less would the
workmen feel heat.—Sir Arthur Markham : Yes; but
the more liability you will have to gob fires, because you
will have the wind drawing through the packs.

Timber a Danger.

Passing on to another question, Mr. Johnstone said
he had found that timber had been a prevalent cause of
fires, and for two reasons ; one was that timber gave off
an inflammable gas at a lower temperature than did
coal, and the gas it gave off was ignitable at a lower
temperature. Then, again, when the props were left in
and the roofs did not subside, as had been pointed out
by a previous witness, the prop standing there, even if
broken, formed a pipe. The fact of the prop being there,
surrounded with gob, meant that the gob did not pack
itself so closely round about the prop as it would if
there were no prop there. It prevented equal settle-
ment and left interstices in the immediate vicinity of
the prop. As the prop heated, that set up a current,
and there was more rapid diffusion of the gases. He
thought all colliery managers as a rule realised the point,
they were constantly impressing it on the men, and an
effort is made to withdraw all the timber. Some man-
agers maintained that all their timber was withdrawn,
but witness doubted whether in any case that was