April 14, 1916.

THE COLLIERY GUARDIAN.

717

both countries. They were all indebted to Mr. Dean
for having brought that subject before them. The paper
should make us think whether there was anything we
could do to make our results approximate more nearly
to those of America. He thought, however, that there
was nothing in the paper to make us believe that we
were lagging behind the Americans in efficiency and in
the provision of labour-saving plant.

Coal Dust Explosions.

Prof. Henry Louis, in opening the discussion on Mr.
Blatchford’s paper (p. 704), remarked that the author
had thrown a good deal of light on the use of various
substances in quenching explosions. He believed that
the original idea of these investigations sprang from
himself (the speaker) in the discussion of a paper before
an institute meeting, when he had compared from the
theoretical point of view boiler ashes and ground shale
or gypsum from the point of view of specific heat, and
heat absorbed by dehydration, and he had then predicted
that either of these bodies would be more efficient for
the quenching of explosions than either boiler ashes or
sand. He thought Mr. Blatchford had overlooked one
of the conditions which might explain some of the
anomalies in his tables. That condition was the state
of fineness of division of particles. It was very puzzling
to find that magnesia was a very much more efficient
quencher than.quicklime, for he should have expected to
find them much of the same order. Could not the fine-
ness of division of these particles be determined?
Obviously, the smaller the particle the greater was the
proportion which the surface which absorbed the heat
bore to the mass.

The President proposed a vote of thanks to Mr.
Blatchford, and the vote was cordially agreed to.

Mr. Jos. Severs observed that he did not think that
the conditions of the experiments were quite those in a
pit. In the latter, one had the roads all dusted with a
quencher, say, flue dust. The process went on week by
week, and by-and-by there were five or six layers, one
on top of the other, and the whole of the stuff was lying
in a condition of rest on the floor and sides and galleries.
There might be an explosion, but, if so, that explosion
was probably due to the fine dust in the pit having been
mixed in the air under conditions conducive to the explo-
sion. Coal dust had a specific gravity of about 1-25.
Shale dust would probably not rise up with the same
rapidity as coal dust, and an explosion might thus occur.
More experiments should be made on lines similar to
those of the pit. For himself, he thought it would be
impossible to use Glau'ber salts, by reason of the expense.
Glauber salts cost 2d. or 3d. per packet, whereas flue
dust cost nothing, and, indeed, they were very glad to
send it down the pit and dust the galleries with it.

Mr. T. W. D. Gregory (Central School of Science and
Technology, Stoke-on-Trent) submitted calculations
which, he thought, tended to prove that the conclusions
arrived at by the author with reference to the value of
the specific heat factor were anything but proved. He
had for years advocated the use of potash alum as a
deterrent, considering it more suitable than any other
substance. It contained large quantities of combined
water, which, unlike soda crystals, etc., it could retain
for long periods at the ordinary mine temperature. It
absorbed large quantities of heat,'owing to the fact that
heat was required to dehydrate the substance, and, also,
to vaporise the water liberated. It also became liquid
on heating, and tended to coat or film the substance in
contact with it.

Mr. J. D. Morgan (Birmingham) stated that the
results in the paper confirmed what had hitherto been
more or less generally believed, but not, so far as he
knew, established by a systematic investigation, namely,
that, apart from considerations of cost and convenience,
the usefulness of an inert dust in diminishing or pre-
venting a combustible dust explosion depended upon its
capacity for heat, and the rate at which heat could be
absorbed by it. Excepting for decomposible inert dusts,
these properties depended upon specific heat and con-
ductivity. The value of the paper would be increased if
the thermal conductivities of the materials mentioned
could be given. He could scarcely agree with the
author that the rate of heat absorption was implied in
the conception of specific heat. Rate belonged rather
to conductivity. In the case of decomposible com-
pounds, the effects of specific heat and conductivity, were
supplemented by, if not subordinated to, the heat
absorption in the process of decomposition. In general
terms, the usefulness of the inert material depended
upon its rate of and capacity for heat absorption, a fact
abundantly supported by the evidence adduced in the
paper. It was interesting to see laid low the old fallacy
concerning materials which gave off carbon dioxide when
decomposed by heat. A little consideration was
sufficient to show how slight was the justification for
that belief. The carbon dioxide formed was practically
a by-product of the explosion, and, consequently, could
not have any more quenching effect than had the carbon
dioxide ordinarily produced in a coal gas or dust
explosion.

Prof. P. P. Bedson (Armstrong College) wrote that he
was much interested in Mr. Blatchford’s careful exami-
nation of the conditions which determined the action of
different substances which could be employed as preven-
tive agencies in coal dust and air explosions. It was
very evident that the mode of action of these quenches
was by no means a simple matter, and the facts brought
forward showed, that chemical decomposition of the
quench by heat was of quite a subordinate influence, if
an influence at all. It would appear that their action
was physical rather than chemical.

The meeting then ended.

MANCHESTER GEOLOGICAL AND
MINING SOCIETY.

A meeting of the members of this society was held
on Tuesday last at the rooms of the society, John
Dalton-street, Manchester. Mr. Leonard R. Fletcher
presided.

The following mew members were nominated for
election :—Daniel Darlington, 212, Marlborough-street,
Ashton-under-Lyne; David Price, Empire Colliery,
Cwmgwrach, Neath; Sydney Rayner, The Marshes,
Atherton-road, Hindley Green, near Wigan; John P.
Thomas, 41, Graig-road, Ynishir.

Economies in Coal Washing : Discussion.

A paper on “ Economies in Coal Washing ” was read
by Mr. Sherwood Hunter. (See page 705.)

The Chairman said the erection of washeries was such
an important part of a modern colliery that any informa-
tion which would add to their knowledge of the plant
was of great interest to those engaged in mining opera-
tions. He moved a vote of thanks to the author, which
was carried.

Mr. Bramall remarked that Mr. Hunter had not
explained how they were to get rid of the dirt after
washing. They were told that the same water could be
used over and over again, but that was not his experi-
ence, which was that if the'same water were used two
of three times the coal became the colour of clay, and
on that account was difficult to sell. The fine fireclay
coated the coal which, after being washed, had to be
syringed with fresh water before it was disposed of.

Mr. Drummond Paton said the paper appeared to be
written on the basis of providing washeries where the
moisture content was over 5 per cent. For several years
he had been endeavouring to bring before the notice
of colliery owners the system of dry dust treatment, and
he read a paper on the subject to the members of that
society some time ago. He also emphasised the
importance of special reference being paid to the section
in which there was the maximum ash in connection with
the washing of coal. Hits experience proved that it was
practically impossible to enrich the coal dust under one
millimetre, and that if that medium were allowed to
pass into the washery they got a thick viscous washing
fluid, with all its attendant troubles, whilst the material
which eventually issued from the washery was not in
any way enhanced in value, especially in the flour dust
section. The flour dust produced a treacly washing
water in which there was no distinctive action, and in
the bulk of cases left a coating of dirt on the washed
nuts which was detrimental from a commercial point
of view.

The Chairman remarked that Mr. Hunter distin-
guished between continuous and intermittent washeries.
By “ continuous,” he gathered the author meant a
washery in which coal was conveyed direct from the
screening plant by a conveyor belt; and by “ inter-
mittent,” one where the coal was loaded into'wagons
from the screens and unloaded again from the wagons
into the washery. It would appear that the first method
was the cheaper of the two, but there were disadvantages
attached to a continuous washery which Mr. Hunter had
made no reference to. The supply of material did not
always come evenly from the pit, and that was an
important point to be reckoned with when the erection
of a washery was under consideration. It was very
annoying to have the pit stopped on account of the
washery being overloaded, when every effort had been
made to provide a plant capable of dealing with all the
slack likely to come from the workings. For some
reason or other the coal coming from the pit contained
more slack at one period than it did at another, with
the result that the washery was overloaded perhaps for
one hour, and had not enough to do the next hour.
Mr.' Hunter recommended washing first, and then
sizing, but in his (the speaker’s) view there was a good
deal to be said for sizing first and washing afterwards,
and he would like to hear the author’s reasons for taking
the view he had done, because the opinion he (Mr.
Fletcher) had formed was that they would get more
efficient washing if the sizing was done before the coal
was sent to the washery.

Mr. Siddall asked if the author intended to convey
that the water was used over and over again when he
stated that “ it had been found possible to work a
washery year in and year out without any outlet what-
ever.” If that were so, there might be a difficulty
owing to the water getting very thick and dirty. He
had had experience of a washery where the fine dust
from a millimetre downwards made all the difference in
the world .to the efficiency of thfe treatment. After it
had been working some time the water became like a
thin cream, or whitewash, and it dusted the washed
nuts, etc., to such an extent that customers would not
have them at any price. The fact that it had been
washed knocked several shillings a ton off the value of
the coal, because it was plastered all over with the fine
dust. An effort was made to extract the dust by putting
in screens, and that increased the efficacy of the
washery, both as to the amount of material put through,
water used, and cleanliness of the coal treated. Very
fine dust was commercially valueless, and if a system
could be devised by which the dust could be eliminated
by means of an extractor before the coal was washed
there would be less water used and a finer product
obtained.

Mr. Stoker said, he should like to know whether the
dust it was desired to eliminate was coal, stone, or clay
dust. The clay or stone . dust caused the water to
become dirty or viscous, but if that dust was eliminated
before washing, it would be interesting to know what
they were going to do with it.

Mr. Drummond Paton remarked that the coal dust so
extracted might in the near future be applied for low-
temperature distillation.

Mr. Stone agreed that, at present,, it was difficult to
know what to do with the extracted dust, which, in a
dry state, was a very nasty commodity to deal with. He
understood that at one colliery it was collected by drums
or a patent vacuum apparatus, but even then, when a
large' quantity of dry dusty stuff was heaped on the
surface, it was really a problem to find a suitable method
of dealing with it. One suggestion might be that it
should be made into briquettes, which was possible where
the dust was of good quality, but it would not apply to
all collieries.

Mr. J. Gerrard said that, to his mind, the question
of fine dust and slurry was a minor one, the important
point being to extract the dirt and make the coal cleaner.
Washeries had got beyond the experimental stage, and
had been established at a great many collieries through-
out the country, with considerable success. Anyone
who had been in the neighbourhood of Newton Colliery
would have noticed the immense heaps of dirt which
had been taken out of the coal, and although in these
war times it might not be so important to have clean
coal, yet in the past owners had been able to get
enhanced prices for their washed nuts. Some of the
difficulties mentioned by previous speakers had been
overcome on the Continent. ’ On one occasion he was
taken by the managing director of the Harpen Company
to one of their largest collieries, where washeries had
been erected, and he was shown a series of settling tanks
used for collecting the fine coal dust, which they had no
difficulty in disposing of when it was removed. In point
of fact, it was almost pure coal, and they had found a
market for it. On the whole, there could be no doubt
that washeries were of great advantage, and paid for
their erection over and over again. Sir William
Garforth, who installed one at Altofts some 20 years
ago, had proved the value of washing coal, and through-
out South Yorkshire, where they made large quantities
of coke, they could not go back to the old days when
coal washing was not in vogue. His opinion was that
.the question of dealing with the fine dust and slurry was
no bar at all to the washing of coal.

The discussion was adjourned to a future meeting.

The Connection Between the North-Western European
Coal Fields : Discussion.

Tn connection with the above paper read by Prof.
Stainier at the February meeting (see Colliery
Guardian, February 11, 1916), a written contribution
was submitted from Mr. H. Bolton, of Bristol. Prof.
Stainier, he said, had rendered a notable service to
British geologists in supplying so masterly an analysis
of the earth movements and accompanying physical
conditions which operated during carboniferous times in
Northern Europe and the British Isles. The clear
determination of these broad tectonic outlines was
absolutely, essential if they were to advance further
towards a better knowledge of the relation of one coal
field to another and to the sequence of development of
the coal measures in any particular area. Prof. Stainier
showed that certain inferences as to the relationships
between coal fields might be reasonably drawn upon
present evidence, and also that more evidence was
required to demonstrate those relationships as unques-
tioned. Faunal evidence had a bearing (not wholly
recognised yet) upon these questions, and must be taken
into account. Two examples might be quoted from the
paper. The physiographical conditions of the Pendleside
period were regarded as contradictory, inasmuch as
” deep sea ” cephalopods (Goniatites) crowded the
shales and Posidonomya were no less abundant. To
that he (Mr. Bolton) might reply that the occurrence of
all stages of growth of Goniatites in the “ bawn-pots ”
associated with the Bullion coal in Lancashire, and the
remarkable suite of nodules charged with Goniatites at
Garre Heys, near Colne, long ago led him to the belief
that Goniatites were not deep-sea forms of coal in coal
measure times, but flourished in inshore waters where
truly littoral conditions prevailed.' The extreme thin-
ness also of some of the marine horizons could hardly
have arisen under deep-sea conditions. Prof. Stainier
also drew attention to the existence of Upper Old Red
sandstone fishes in rocks at Southall boring, which
lithologically were of Lower Old Red sandstone type.
That occurrence was somewhat similar to what he had
already described in connection with the Kent coal field
where a Farington fauna was associated with Pennant
grit types of rocks. In each case physiographical con-
ditions must have furnished the factors that enabled the
association to be possible. The paper would no doubt'
do much to clarify their conceptions of the southern coal
fields and their inter-relationship, and aid materially in
future work. He congratulated the author upon his
contribution to the Transactions.

The discussion was further adjourned.

Partnerships Dissolved.—The London Gazette announces
dissolution of the following partnerships:—R. Hollands, J.
Hollands, and D. Hollands, coal merchants, as R. and J.
Hollands, Eshton-road, Eastbourne; H. Dewhurst and W.
V. Dewhurst, founders, as Dewhurst Brothers, Warren-
street, Sheffield.