April 30, 1915.

THE COLLIERY GUARDIAN.

913

to understand the system. They had a certain area of
coal, and on Mr. Paton’s system they ought to drive to
the boundary, work out the coal, and leave their troubles
behind. But that was not the practice with a thin seam.
In a seam representing any thickness up to 9 ft., they
worked the seam before them, and as a rule they were
not troubled with fires. What he was anxious to get at
was how much per ton the stowing was going to cost,
and especially how much was it going to cost, when the
system was finished and in operation, more than it cost
now.

Mr. Paton, replying, said he reckoned in an ordinary
case that they were dealing with a shaft having a depth
of 200 to 300 yds., and they were using a length of pipe
from 1,000 to 1,500 yds., and ’had a fair roof. They
could get the stowing done for 6d. per ton, covering the
putting in of the material, and including the charge for
the plant. In those big seams on the Continent some
of the plants were very expensive. But it was possible
to put in a primary plant at a very much lower cost.
Part of the expenses of those foreign plants were due to
special circumstances, the location of the collieries, and
the formation of the seams. Replying to other ques-
tions, the author said that there would be a surface
contraction of 2 to 5 per cent. But if they got the best-
material it would not exceed 2 per cent. That, however,
depended on the class of materia], depth of mine, etc.,
and in some cases it might run up to 10 per cent. It
would be possible if the angle were anything like reason-
able to work on three' faces, as already applied in
Germany, Austria, etc.

Mr. Clark remarked that in the South Staffordshire
thick coal there would be a difficulty in dividing the
workings into three faces, because the area consisted of
14 different seams. It would be necessary to deal with
the top portion first, and leave the bottom till last. That
was what was being done at Old Hill, where the coal
was nearly all gone.

Mr. Hugh Johnstone said that if they employed
hydraulic pressure they might have bending without
breaking of the top coal, and it was difficult to see in
that case how gob fires would result, as the goaf being
completely packed, the air would be excluded.

Mr. Clark said that in some portions of the Stafford-
shire district, if they were to work the bottom coal first,
they would spoil the top coal. He was unable to speak
from experience with regard to the Old Hill district, but
he knew enough of it to know that if they did not get
the top first, they were apt to lose it. The only thing
that caused him some doubt was the question of cost,
because if they were going to refill those large spaces
they would have to fill in an immense amount of stuff,
and the process was likely to be very expensive. He
was very much impressed with the possibilities of the
system for thick coal, if the cost was not prohibitive.
The author had referred in the paper to certain thick
coal workings that had been abandoned in the South
Staffordshire district. He assumed the author was
referring to the second and third workings in the South
Staffordshire thick coal, where he seemed to think there
were open spaces. This, however, was not so; the spaces
between the pillars had fallen in, and become practically
consolidated, before the second workings commenced.
He did not think this system was applicable in thick
coal second or third workings.

Mr. Paton said he was not thoroughly conversant with
all the details of the various coalfield, and that was why
he asked for suggestions and information, but he thought
it was well worth looking into, and well worth a certain
number of experiments, and he could not help thinking
that it was entirely a question which the institute might
take up for the purpose of a thorough investigation.

Mr. Forrest said that mention had been made of 6, 7,
and 8 ft. seams in which coal cutters were employed.
He could give instances of such seams, because he was
working coals in seams varying from 3 to 7, 8, and 9ft.,
and he entirely agreed that if those seams had to be
packed, they must be packed very tightly. A great deal
of practical investigation would he required by Mr.
Paton before he could apply that system to the Stafford-
shire district. At present he knew of no face that was
moving 6ft. per day; if they could move that distance,
no doubt they would save considerable timber by the
avoidance of top and bottom troubles. He would like
to know what were the actual running costs.

Mr. Paton said there were very few cases where the
costs ran up to 2s., but that might happen in a public
area where the stowing was necessary for the protection
of residential buildings. In some of the cases where
the stowing was undertaken, the floor was originally so
bad that it was possible to insert the arm up to the elbow
in fissures in the floor. In that case the material used
was rather crude shale. Difficulties were apt to arise if
they had to deal with an oily shale. There was generally
enough moisture in many seams to serve for the carry-
ing out of the system. It was quite true that things
were carried out on a very large scale on the Continent.

Mr. Forrest said that rather confirmed the view he
had already taken, that the foreigners had more money
to spend.

Mr. Paton said he was not sure of that, but certainly
the Germans and the Russians got more out of their
coal in the way of energy. That was particularly the
case with regard to the Westphalian coalfields. Where

the English people got 30,000 to 40,000-horse power out
of a given amount of coal, the Germans would get
70,000, and it was that class of colliery which was
making the fullest use of the stowing system.

Air. J. T. Stobbs (North Staffordshire) said there was
another aspect of the question that had not been touched
upon during the discussion, and that was the public
aspect. The coal question was not a matter which
affected merely coal owners and coal miners, and any-
thing that would prolong the duration of our coal
supplies was something that would be considered, if
necessary, by the State itself. In South Staffordshire
certain existing methods had been pushed to the limits
of their efficiency, and new methods of dealing with the
thick coal would have to be considered. There was no
doubt that present methods were wasteful, involving the
loss of much coal for various reasons, such as gob fires,
railways, surface property. In the northern part of the
coalfield — in Cannock Chase — there were many coal
seams which could not be worked by existing methods,
and which must also be left in for ever. Some new
step would have to be taken if those coal seams were to
be gotten, and that ought to be considered, because
from the national point of view they must be worked.
It must be borne in mind that the method of hydraulic
stowage which Air. Paton had just described was no
longer in the stage of experiment, and it seemed to be
specially suitable for cases of extraordinarily thick coal,
or coals that were situated jiear heavily watered strata,
as were a number of seams in Cannock Chase and South
Staffordshire, where there was very little cover between
those seams and the heavily watered Bunter con-
glomerates. He could not help thinking that some
totally new method would have to be adopted in such
extraordinary conditions, because the present methods
were wasteful or totally unavailable.

Air. S. H. Cashmore enquired as to the desirability of
installing in-bye stowage. With regard to suitable
materials, no doubt their present spoil heaps would be
very useful, and they had to look a little further ahead,
and consider the state of the ordinary subsoil when those
heaps were disposed of. He gathered from the paper
that it was customary to stow the whole area where coal
had been extracted. He would like to ask whether it
was really necessary to do that. At the present time
it was not customary in the case of a longwall face to
deal with more than 45 to 50 per cent, of the area. He
did not know whether that could be done by hydraulic
stowage. It would be interesting to have the approxi-
mate cost of a plant dealing, say, with 1,000 tons per
eight hours, and allowing for 2,000 yds. of pipes.

Air. Paton, replying, said it might be possible to
furnish a heavy crushing plant dealing with about 60
tons per hour for about <£1,250. That did not take any
account of the cost of material. A great deal would
depend on the conditions, and as to whether the material
was uniform. There was no reason why the system
should not be absolutely under control.

The Chairman said he would like to propose a very
hearty vote of thanks to Mr. Paton for the extremely
interesting paper he had given the meeting. He had
introduced an entirely new subject, which had led to a
very interesting discussion. Undoubtedly the district
was very interested in that proposal. But they must
remember that the installations exhibited were on a
gigantic scale. In the Staffordshire district they were
more concerned with smaller areas, perhaps of 200 or
300 acres, where the coal had to be left owing to build-
ings on the surface. In other cases there were upper
seams which had to be left on account of danger from
the water in the gravel beds lying .above. He would
like to see the problem tackled on a small scale, and that
might lead to its ultimate adoption in a much larger
way.

Air. Forrest said he had very much pleasure in
seconding the vote of thanks. He did not remember
having heard a paper or discussion which had been so
instructive, or which had introduced so many new ideas.
He was still somewhat in the dark as to why the scheme
had been so extensively adopted in foreign countries,
where conditions were otherwise favourable and labour
was cheap. If he might venture to suggest to Air.
Paton, it would ’be advantageous to go more deeply into
the subject, and find fresh reasons for the adoption of
hydraulic stowing. They could not expect Air. Paton to
go into all the details, but, at the same time, they must
all remember that it was detail that mattered most in
colliery work. He felt sure the mining engineers
generally would welcome Mr. Paton, and they hoped to
have a visit from him when he had been to Scotland.
As they were aware, Scotsmen were very particular
what they spent, and if Scotland could make the thing
a success, there would be some inducement for Stafford-
shire to follow.

Air. Clark said he would like to take the opportunity
of supporting the vote to add a few words with regard
to some remarks made by Mr. Stobbs as to South
Staffordshire. He thought gentlemen from other dis-
tricts had a rather exaggerated idea of the waste occur-
ring in South Staffordshire. No doubt in years gone
by nothing but the very best coal could be sold. No
one would buy it, and that was doubtless the reason
why some of the poorer seams were closed, and the
coal was left because it was not then of com-
mercial value. If coal in South Staffordshire 60
years ago had been as valuable as at the present time,
and that system of hydraulic stowage had been in force,'

and it had proved itself as valuable as had been repre-
sented to them that day, no doubt there would have
been a large saving to the country, because very
much less coal would have been left behind. He hoped
experiments would be made in the Warwickshire dis-
trict, as well as in the Black Country, to see whether
the system of hydraulic stowage was applicable. They
owed a debt of thanks to the author for placing his
knowledge at their disposal.

The resolution was carried with acclamation.

Air. Paton, in acknowledging, said he was very
grateful to them for their appreciation. He would
remind the President that he had described one of the
simplest of plants in operation at Wish aw when he gave
his last paper at Alanchester. With regard to the future,
all he wanted to impress upon them was that if this
system was being adopted in 500 or 600 seams by other
countries, there must be something in it, and it must
at least be worth their consideration. With regard to
the abandoned seams of Staffordshire, there was a
possibility of their becoming valuable from oil develop-
ment. Oil was increasingly necessary, and those seams
should be investigated from the point of view of oil
production. There was no doubt a high volatile content
in many of the coals, and it should be possible to extract
that valuable oil, and so make use of the poorer coals.
It would be found possible to carry out low temperature
distillation very successfully, and he already had cases
in hand where the oil returns were highly satisfactory,
and promised a great future.

Association of Mining Electrical Engineers. — The joint
meeting with the National Association of Colliery Managers
and the Notts and Derbyshire branch of the Association of
Mining Electrical Engineers, on Mr. Scott’s paper, “ Pro-
tective Devices,” has been postponed from April 24 to
May 8, at the University College, Nottingham, at 3.30 p.m.
prompt.

Standard Specification for Gas Coal.—Mr. Dugald Currie,
gas engineer, Airdrie, presiding at the 32nd annual informal
meeting of Scottish Gas Managers, raised the question of
standard coal specification and conditions of contract. He
said that the present time was most opportune to consider
the advisability, or otherwise, of introducing a standard
coal specification and model form of conditions of contract
which could be used by all undertakings when purchasing
their supplies of coal. It was quite true that many under-
takings purchased coal to their own specification and con-
ditions of contract, but he was strongly of opinion that were
they to adopt some standard form of specification and con-
ditions of contract, their position as large coal purchasers
would be considerably strengthened. To illustrate the
weakness in the present system, it was only necessary to
remind them of the commonly phrased advertisements which
appeared in the technical Press and in the newspapers from
time to time inviting tenders for the supply of, say, screened
coal. In cases where such tenders were received and
accepted without having a detailed specification of the
manner in which the coal was to be screened and handled,
it stood -to reason that the coal master was practically given
power to screen and handle the coal very much at his own
discretion. It frequently happened that gas managers,
previous to entering into contract for their supplies, obtained
trial wagons of the coal they were interested in for testing
purposes, and as the coal generally supplied under these
conditions was well screened and perfectly clean, the results
obtained sometimes turned out so satisfactory that perhaps
a large order was placed. The manager having tested the
trial wagons naturally expected to be supplied during the
currency of the contract with coal of equal quality, but in
many cases his expectations were rudely shattered, as, not
infrequently, supplies were given which could come neither
under the category of being screened nor well handled. In
connection with supplies of washed fuel, such as nuts, they
again placed themselves very much in the hands of the
coal masters, as he was not aware of any recognised stan-
dard being adopted, even by the coal masters themselves,
as to the mesh or width of opening in the screens to pass
the various sizes of nuts which they sold. On the other
hand, they invariably received deliveries of washed fuels in
a very wet condition, and although he understood that some
collieries made due allowance for the excess of moisture in
the fuel, there were others who made little or no allowance,
with the result that in many cases they had frequently to
pay for the weight of water or moisture which was contained
and delivered with the fuel. Again, in connection with
deliveries, they were not much better off, as they had
generally to accept the coal masters’ excuses for non- or
insufficient deliveries, without having facilities to test the
accuracy or inaccuracy of their statements. When pressing
for deliveries, it was quite a common excuse for coal
masters to say that the output had been reduced or stopped
through accident or breakdown at the pit, and, consequently,
deliveries were reduced or suspended; and the manager so
affected was, under the present system, generally not in a
position to verify or contradict such excuses, with the result
that these excuses might be put forward at times when the
coal master was anxious to take advantage of a firm market,
irrespective of the inconvenience he might cause the gas
undertakings which he had agreed to supply. He (Mr.
Currie) would suggest that the question of inaugurating a
standard coal specification and model form of conditions of
contract should be seriously considered by the council of the
North British Association of Gas Managers.—In the dis-
cussion that followed, Mr. A. Yuill, Dundee, said he did
not think they would ever be able to prevent all defective
supplies. They could not say to the coal masters that they
must pass all the coal required through a given size of screen.
He thought if the coal master gave a sample of coal that he
was prepared to supply, and if that coal was suitable for
the purpose, they could then arrange with him, and it then
lay with them to see that he fulfilled the contract according
to the sample they had got. The model form of conditions
of contract ought to be considered by the council of the
North British Association of Gas Managers, because it was
a matter which affected them all.—Mr. J. B. Scott, Cowden-
beath, said the difficulty that appealed to him was that
coal was not a manufactured article. The coal master had to
take the coal from the mine just as he found it. That went
a long way against trying to get a standard specification.