June 22, 1917.

THE COLLIERY GUARDIAN.

1171

would show what had happened. Evidently one had
to examine samples here and there. One dared not
assume that if one got a sample of a certain seam at a
certain place, the seam was going to be the same some
distance further on. It might vary considerably in
composition and in its tendency to firing. Mr. Carlow
had referred to the cracking of hard splinty coal, and
Mr. Mowat had made reference to what was very much
like the same question, and had given an instance of
water coming through a seam of coal, in situ, 250 fms.
deep. That was a quarter of a mile, and the water was
apparently leaking through from submarine workings.

Mr. Mowat said that in one place 8 ft. wide it
squirted across from one side to the other, and con-
tinued till all the works was run over.

Dr. Haldane said that that was a very remarkable
observation. As far as he knew, it was an exceptional
case. Usually a barrier of coal which was not very
thick would keep water out.

Mr. Mowat said that the cracks were quite open
cracks in hard coal.

Dr. Haldane said that was a point which he had
often wondered about himself. All he had seen of coal
was that, as a general rule, it was not only airtight,
but watertight as well. With most seams he thought
that was the rule, that a comparatively small barrier
of coal would keep water out.

The President agreed with Air. Mowat that the coal
in Lanarkshire was extremely pervious to water, and
very large barriers were necessary to hold the water
back.

Dr. Haldane said that was very interesting. He
supposed it was Mr. Mowat’s idea that the coal had
definite cracks in it.

Mr. Mowat said that was so. He might say that on
two occasions in that seam he had done his very best
to get the water to come through, and had failed in
both cases.

Dr. Haldane asked Mr. Carlow if he did not think
his coal was cracked before.

Mr. Carlow said he thought it gradually cracked
over the period of years.

Dr. Haldane asked if that were another kind of
splinty coal.

Mr. Carlow said that was the case. It was not the
same seam.

Dr. Haldane said that that case was really analo-
gous to the case of the Hamstead Colliery, where they
used to get fires developing on the main intake road as
much as 30 or 40 years after the road had been driven,
just through cracks occurring. He remembered a fire
in the main return which cost a great amount of money
to the company on account of the loss of coal. It sud-
denly broke out through one of the cracks opening out
on an old road which had been driven for 30 years. He
would not venture to say anything on the subject of
hydraulic stowing. He had seen a good deal of
hydraulic stowing in Germany, but he had never tried
to go into the question. One knew what a difficult
thing it was sometimes. It might be easy, or it might
be almost impossible. Of course, if one could have
hydraulic stowing, say, in South Staffordshire, where
the thick coal was down 2,000 ft., one could solve many
problems there. But sand, and plenty of it, or some-
thing similar, at a cost of practically nothing, was
required to do it successfully. Mr. Forster Brown
had asked a question about testing coal at Doncaster
with regard to oxidation. He thought that was
a sort of thing that ought to be done in labor-
atories in different parts of the country. At Don-
caster they carefully tested their own coal — the
Barnsley seam — and they had tested a great many
coals from different parts of the country from the
general scientific interest point of view, in order to get
comparative data. He was sure that the laboratory
testing of coal with regard to oxidation would give
information which would be of considerable value in
coming to a decision. But their staff at Doncaster
was rather limited as yet. He thought it was an argu-
ment for establishing laboratories in different districts
in order to get that sort of thing done quite easily,
without any trouble, whenever it was required. Mr.
Mowat had raised a point about some experiments
with artificial resistance. He himself had often
thought of Murgue’s equivalent orifice theory, and as
to whether it really did apply to the mine as a whole;
and though he had never tried it himself, he had been
assured by very competent people that Murgue’s equiv-
alent orifice theory did work out for the ordinary
ventilation of a mine. If one put in an artificial
resistance of, say, small coal or material of that sort,
one got air through that which undoubtedly did not
follow the equivalent orifice theory.

Mr. Mowat said that if the narrow spaces for air
were put in in series in order to baffle eddy currents,
the variation in quantity of air was directly in accord-
ance with the pressure and the square root rule. His
difficulty was to understand how and when the square
root law changed to the direct law.

Dr. Haldane said there was some point in the size
of the lumps of coal where there was a transference
from the square root law to the direct law. If one
took air through cotton wool, which was very porous
and allowed air to pass freely, it would be found that
the flow varied directly as the pressure.

Mr. Mowat said that was a similar case to small
coal.

Dr. Haldane said that if one took sand or small
coal, pretty fine stuff, that law still held, namely—that
the flow varied directly as the pressure; but with
lumps of coal of a certain size the square root began to
operate, and when they got large, and the air was just
buffeted about from one surface to the other, the ordi-
nary square root law obtained. He did not know at
what coarseness of the coal the transition from one law
to the other took place.

Mr. Mowat said it almost looked as if, with air
pores, if one got them ,small enough, a double quan-
tity was obtained with double the pressure, whereas,

with larger ones, four times the pressure was needed
to get double the quantity.

Dr. Haldane said if there were an air wave of any
decent size—an ordinary pipe, for instance—it
followed the square root law. At least, that was his
experience; but if one ventilated through a goaf, with
the leakage through the coal and through the porous
material, the direct law would be followed, if there
was a large amount of leakage. He thought that most
of the leakage in a mine was gross leakage through
holes; one heard the air whistling through. There
was also a very slow current through porous material.
He did not think the amount was great, otherwise
Murgue’s theory would not work out in practice so
well as it did.

Prof. Arnold Lupton wished to ask one question
with regard to the variation from the square root law
to the direct pressure law. Was it the correct explan-
ation that when there was a certain velocity, and the
air met with an obstruction, it was stopped and velo-
city had to be re-imparted? That could only be done
by a pressure varying as the square root. But if the
velocity were very slow, it might be that owing to the
slowness of the velocity the re-imparting of velocity
was such a small factor that one came to true friction
as distinguished from the re-imparting of velocity,
which was not true friction.

Dr. Haldane thought that that was the root of the
matter.. It was the viscosity of the air which told,
and which might be called friction when the passage
was extremely small, and where the air was closely in
contact with the solid, through the chinks of which it
was passing. In the other case, where there was a big
space, and the air met with all sorts of obstructions,
it was as Prof. Lupton had suggested, so far as he
knew; but.he did not profess to have gone into the
physics of it. He was only referring to the fact with
regard to the flow of air, which was undoubted. A
number of other questions had been raised in the
course of the discussion, but he thought he had better
not attempt to deal with one or two of them, because
he was quite incompetent to throw any further light
on them at present. There was one thing which he
had forgotten to mention. He did not at all agree
with Mr. Winmill’s remark as to where the credit lay.
It was not only the fact that a great amount of work
had been carried out by Mr. Winmill and Mr. Graham,
but the amount of brains which they had put into it
was enormous. It was perhaps better known to him
than to anybody else, and he had always considered it
an absolute duty that they should get the credit for
the work, and for the brains they put into the work.
He himself got heaps of credit. It was often the case
that a young man who took enormous trouble over the
work never got proper credit for it at all. He thought
that was not in the public interest. They had only to
read the papers to realise the value of the work. Then
Mr. Winmill’s apparatus for observing the rise of
temperature in coal on a small scale was a lovely piece
of work; it was simple, but extraordinarily effective.
It was a delightful experiment to see the coal on the
laboratory table and watch the thermometer rising as
the coal oxidised. The members of the institution
were able to see that two years ago. He admitted
that Mr. Winmill had doctored it up a little bit. He
had wanted .the experiment to go really well, and had
therefore mixed up a bit of pyrites with it, and then
it went beautifully. One could see the thermometer
moving. All those apparatus were due to the genius
and hard work of Mr. Winmill and Mr. Graham.

This terminated the morning session.

(To be continued.)

Industrial Developments in Corea.—Concerning articles
which have appeared in recent issues of the Herald of Asia
relative to industrial development in Corea, H.M. Consul-
General at Seoul (Mr. A. H. Lay) remarks that he thinks
the writer of the articles is justified in his expectation of
considerable industrial activity in Corea in the near future.
Corea is now an agricultural country, but, while agriculture
is likely to remain her greatest asset, the existence of cheap
and abundant labour, side by side with undeniably great
natural resources, make possible a considerable expansion
in other branches of industry. Present indications seem to
pomt to Ping-yang and the banks of the Dai-do Biver.
with Chinnampo as the outlet, as the future industrial
centre of Corea. There are coal and iron mines in the
vicinity,.and Ping-yang is connected with Chinnampo both
by rail and river. Sai-nei is the place at which the iron
mines owned by the Japanese Government are situated.
These mines produced 73,611 tons of ore during January-
September 1916, as reported in the Board of Trade Journal.
A company has been formed to work anthracite coal mines
which it has recently acouired in the Ko-sai district,
South Hei-an Province. It is estimated that some three
million tons of coal are to be found in these mines.

Decreased German Goal Output.—The Kolnische Volks-
zeitung publishes a statement by the Imperial Commis-
sioner explaining the causes of Germany’s coal difficulties.
The Commissioner said that, owing to the lack of trained
railwaymen, the daily supply of coal in Upper Silesia had
fallen to about half, that of Westphalia from 21,000 tons
to 8,000 tons. Then winter came along, with prolonged
consumption of coal. When the water service started again
the personnel available for Upner Silesia was found insuffi-
cient, while the situation in Westphalia was complicated
by food difficulties and labour movements. The situation
had been further aggravated by the campaign against
Boumania, which had necessitated the despatch of enor-
mous coal supplies, and by the intensified U-boat warfare,
which had obliged Germany to deliver coal to neutrals
who had previously been supplied by England. Not a
single ton of coal left Germany without Germany’s receiv-
ing an equivalent. The Commissioner also said that mili-
tary events at the front had prevented miners from return-
ing home who otherwise would have been available. In
the coming winter there must be no luxurious consumption
of coal. The supply should suffice if the people would
heat only a limited number of rooms, perhaps even only
one room.

REFRACTORY MATERIALS
COMMITTEE.

The report of this committee states that during the
past year the provision of the necessary apparatus at
the County Pottery Laboratory, Stoke-on-Trent, under
Dr. Mellor, has made considerable progress, in spite of
difficulties in obtaining delivery of apparatus. The
necessary plant for the investigation of the question of
refractoriness of material under load, and of the
differences in sizes of bricks when cold and when at
high temperature, has been completed for some time,
and research in these respects commenced. The
apparatus for investigating the influence of fine flue
dust carried into the setting on the refractoriness and
life of the materials employed is now also practically
complete.

In previous years the work done has been chiefly
carried out on manufactured materials obtained from
different makers or on material taken from deliveries
to different gas works. As stated in last year’s report,
it had been found essential to employ in the work, in
addition to such material, bricks which had been manu-
factured from known materials and under exactly
defined conditions, and Dr. Mellor had been authorised
to arrange for the manufacture of such bricks. A
large quantity of clay, amounting to about 20 tons,
has been obtained from six sources, representative of
the different varieties of material found in the United
Kingdom, and has nearly all been made into bricks for
testing purposes. The method of manufacture has been
varied for the different qualities of clay both in respect
to the quantity, fineness, and firing temperature of the
grog, and in the firing temperature of the finished
brick. The bricks, thus made in such a manner that
their “ life-history ” is known, will be employed by
Dr. Mellor in the various researches now in progress.

Sets of 100 of different kinds of bricks are also being
fired in industrial furnaces at about 1,300 degs. Cent.,
five of which are removed after each firing (extending
over eight days). When the 20 firings are completed,
the bricks will all be examined to observe deterioration
according to the length of time of firing.

The results of hot and cold measurements of typical
commercial firebrick cast some doubt on previous
measurements of the coefficient of thermal expansion
of firebricks and related material at high temperatures,
as the true thermal expansion is obscured by effects
due to the after-expansion or aft er-contraction of the fire-
brick which is taking place while the bricks are being
measured. The work demonstrates the importance of
taking into account the continued alteration in the
character of bricks under prolonged or repeated
heating.

A number of measurements of the after-contraction
or expansion of firebricks have been made to test the
conditions laid down in this respect in the standard
specification, and the general conclusion is that the
tendency is for ordinary silica bricks to give a less expan-
sion, and firebricks of fireclay to give a greater contraction
in the reducing than in the oxidising atmosphere.

The question of modifications of the standard
specification has been further considered, but it was
felt that under existing conditions, it would be inoppor-
tune to make any material changes in the tests
specified; two alterations have, however, been made in
the specification relating to retort material. The
wording of the specification relating to the material
to be employed in the manufacture of retorts might
be taken to preclude the admixture of silica-material
with the fireclay used for retort manufacture. To
prevent any misconception on this point words have
been added permitting the use of silica-material, and
Clause 1 now reads as follows : The retorts or retort
tiles shall be made of sufficiently seasoned raw clay
compounded with clean burnt clay or grog; they may
also be made from suitable silica material. No “ grog”
shall be used which will pass through a test sieve
having 16 meshes to the linear inch. It has also been
agreed that, in addition to a minimum porosity of
18 per cent., a maximum porosity of 30 per cent, shall
now be specified.

The sub-committee appointed to report on the extent
of research work on refractories already in progress,
the facilities for research existing in this country, and
the facilities existing for collecting published informa-
tion on refractory materials and making it generally
available, has received from the council of the Institu-
tion of Gas Engineers the following schedule of
problems calling for immediate action:—

(a)	Effect of loads on refractoriness of firebricks at
industrial furnace temperatures.

(b)	Difference of size in firebricks when cold and when
at high temperature.

(c)	Study of clay used for jointing purposes.

(d)	Investigation of the relative effect of an oxidising'
and reducing atmosphere on the refractoriness of fire-
resisting materials and on their permanent expansion or

. contraction.

(e)	The effect of firing temperature on the subsequent
refractory qualities of the goods.

(/) The influence of the flue dust carried into the
settings with the furnace gases, and of the mineral
constituents of the coal carbonised, on the refractoriness
and life of the materials employed.

(g)	The thermal conductivity of the various kinds of
fire-resisting materials at different temperatures.

(h)	Investigation of the effect of the admixture of
highly-siliceous rock, such as ganister (raw or calcined)
on the working qualities of fireclay goods.

(i)	Further investigation of the most suitable means
to be used in the manufacture of the retorts used for
carbonisation of coal, in order that these may withstand
satisfactorily the very frequent and sudden fluctuations
to which they are exposed, owing to their periodic filling
with cold coal when at high temperature, and at the
same time to render them as impervious as possible to
the passage of gases through the retort walls.

A commencement has been made on the investigation
of most of the above matters by Dr. J. W. Mellor at
Stoke-on-Trent on behalf of the Joint Refractory
Materials Committee of the Institution of Gas Engineers
and the Society of British Gas Industries.