February 20, 1914j.

THE COLLIERY GUARDIAN.

405

some such manner that the whole of its power would
not, as at present, be exerted in the wrong direction ?

. Coaid as t from the screens was carried into the
air-current, simply because it had gathered at such a
point that the suction at the top of the downcast shaft
drew it into the shaft. If, therefore, the stonedust was
to be distributed in the same manner, the stone-crushing
plant should be in the near neighbourhood of the down-
cast shaft, or, better still, in a shunt connecting the
surface with the downcast shaft in much the same way
as the fan drift usually connected with the fan inlet with
the upcast shaft. Or, if suitable fluedust was available,
this could be deposited in a drift or shunt leading from
the boilers to the downcast shaft.

The Coal Mines Act of 1911 required that the tubs
should be so constructed and maintained as to prevent,
as far as practicable, coaldust escaping through the
sides, ends, or floor of the tubs, although any tub which
was in use in any mine at the date of the passing of the
Act might, notwithstanding that it was not so con-
structed, continue to be used in that mine for a period
of five years from the said date. That provision fore-
shadowed the introduction of a closed tub. The design
should not be left to Parliament. He thought that
managers, in their own interests, should forestall any
such legislation and anticipate it in such a way that the
tub produced to their own design should be cheap,
convenient, and effective. Open-ended tubs had never
found favour in the north of England. A good iron
tub, however, with normally open top, such as that
usually employed in the north, seemed to be as good an
arrangement as could be adopted, provided that the tubs
were not loaded above the level of the tub itself.

The writer proposed that managers should anticipate
the closed tub foreshadowed by the Act and improve
upon it. A store of inert dust should be taken nightly
to the haulage landing of every district. During
working hours the landing-lad could do all the rest if
provided with a number of shallow trays made of
galvanised sheet iron and fitting the tops of the full
tubs. In each of these trays he would place a few
handfuls of the inert dust. These light trays, fitted on.
the tub tops, would practically transform the present
open tub into a closed tub. The tray alone would
prevent the coaldust from being removed from the tubs
by the air-current, whilst the inert dust reposing in the
tray would be shaken up as it travelled and be carried
away and deposited by the incoming intake current of
air. There was no reason, provided that the buoyancy
of the inert dust was sufficiently marked, why the stone-
dust treatment, conducted on such lines, should not
penetrate into every obscure hole and corner which had
hitherto been accessible only to coaldust. When such
a course of treatment had been in operation for some
time, expensive stone-crushing plants might possibly be
dispensed with. Much manual labour now employed in
distributing stonedust might be more profitably placed,
and the mine would be eventually so adequately
stonedusted that its efficiency in that respect might
conceivably be maintained by simply utilising the
drilling-dust made by the stonemen. An easy calcula-
tion would show that, at many collieries working thin
seams and producing large outputs, the weight of the
stone drillings produced per annum could not be less
than several hundred tons.

One method that might be adopted had been outlined,
but the system possessed great elasticity. It would
here be sufficient to describe another method which
differed slightly from that just sketched out. In the
first place, it was suggested that the screens had
probably been blamed far more than they deserved. It
appeared to the writer that the coaldust carried in the
downcast air-current was obtained principally from the
load within the cage, and in a less degree from the
screens. Although the cage was always roofed,' anyone
who had happened to “ ride ” in the shaft when the
winding engineman had permitted the cage to travel for
a few moments at “ coal work,” would be fully aware
that a strong blast of air was propelled through the
passages of the cage in such circumstances. When the
cages were travelling in the shaft at an average speed
of 30 to 40 feet per second, and in some instances reaching
a maximum speed of from 60 to 80 feet per second,
whatever dust remained on the tub tops must be swept
off into the shaft and carried downwards by the current,
which in the shaft generally travelled at high velocity,
and in the opposite direction to the loaded cage; hence
the force of the down-going current on the up-going
tubs was equal to that developed by the air-velocity and
the cage speed combined. Bearing that state of affairs
in mind, the writer submitted that, in a few cases, a
better plan would be to leave the trays of stonedust on
the full tubs at the bottom of the shaft and let them
remain there until the tubs are banked. They would be
sent down loaded on the tops of the empties. It
appeared quite probable that, if that method were
adopted, the down-going current would sweep the stone-
dust off the ascending trays in precisely the same
manner it now swept the coaldust from the ascending
tubs, not only within the shaft proper, but in greater
degree, as all mining men had experienced, at that
point where the cage reached the normal surface and
the air of the atmosphere was sucked into the colliery
shaft.

If it were true, as suggested, that the current entering
and traversing the downcast took most of its dust from
the top of the tubs and least from the screens, it
followed that the shunts or drifts suggested in the
previous arrangement need not be made, because
sufficient inert dust would be obtained in the downcast
current from the trays of stonedust resting on the tub
tops. Further, it was by no means an indispensable
part of the arrangement that stonedust in bulk should
be taken into the landings at all. The trays could be
filled from a hopper containing fluedust and placed just
above the landing stage, so that each tray, after being
placed on the top of its empty tub, could be replenished

with the inert dust, of which, of course, it would only
be necessary to place one or two handfuls on each tray.
The empties covered in that way would descend the pit,
and the trays would not be removed until the tubs
reached the landings, or even the flats, as the manager
might decide. At the flat or landing, the tray, still
containing some of the inert dust placed upon it at the
surface, would be transferred from the empty to the
loaded tub and sent out-bye on the train.

The construction of such a tray would be as simple
as that of an ordinary domestic “ blazer.” It must be
remembered that it would have to be easily portable.
To make one for a tub measuring internally, say, 42 in.
in length by 36 in. in width would require a piece of
galvanised sheet iron or, better still, of very mild steel—
steel because, strength for strength, it is lighter than
iron and also rather stiffer, but very mild, because that
kind of steel would be most easily workable by the
colliery blacksmith. To make a tray for the size of tub
indicated, a sheet of mild steel 47 in. long by 38 in. wide
would be required—that is to say, a sheet 5 in. longer
than the internal length of the tub and 2 in. wider
than the internal width. As the tray had practi-
cally no work to do, its thickness need not exceed
■Jg in., and probably it would be found that a lesser
thickness would be ample. The deposition of coaldust
would be practically abolished by the use of the empty
trays alone; but whatever dust was actually deposited
would be the inert dust blown from the loaded trays.
There was no reason why the use of these trays should
not extend from the surface right up to the putters’
flats. It would probably be found that, in some few cases,
if the trays received their contents on the surface, the
suction of the intake current at the top of the downcast
shaft might be powerful enough to sweep off the whole
contents at one swoop. In that circumstance the better
method was that first described—namely, to take the
inert dust to the landings and replenish the trays at
those points. In the majority of cases, however, the
second was the handier and more economical method—
that was, to replenish the trays at the surface by means
of a hopper placed at any suitable point on the heapstead,
and above the tracks laid for the empties.

Dr. John Harger (Liverpool) wrote expressing his
pleasure that someone bad come forward with sugges-
tions of a method which he had long advocated. An
ounce of fine stonedust, floating in the air of an intake
haulage road, was of more use than a hundredweight of
coarse stonedust on the floor and sides. Mr. Halbaum,
however, was wrong in stating that the most dangerous
dust was that found on the main haulage roads. The
writer’s experience was that it was found at or near the
working face. He believed that Mr. Halbaum’s scheme
would ensure a continuous supply of stonedust even at
the working face.

Mr. John Morrison (Newcastle) averred that the
paper was rather a suggestion for a closed tub than a
practical scheme of stonedusting, inasmuch as the same
object would be attained if the stonedust, sufficiently
fine, were shovelled into the roads in sufficient quantities.
As to the prevention of the escape of coaldust from the
full tubs, that could be attained by the spraying of the
full tubs. There must be care taken, he added, to
ensure that the stonedust selected was harmless to
respiration.

Mr. T. A. Southern (Cardiff) thought that Mr.
Halbaum had hit upon a happy solution of the problem
of applying stonedust. He did not think that it was
essential that stonedust should be as buoyant as the
finest coaldust. It was regrettable that the Home Office
was conducting its experiments in such an outlandish
place as Eskmeals. He thought that the Home Office
could easily have found a suitable site in Yorkshire,
sufficiently remote from public dwellings and highways,
and yet easily accessible by rail from all the great
coalfields.

Mr. Leonard Fletcher generally commended Mr.
Halbaum’s suggestions, although seeing difficulties as to
the fitting of the trays on the tubs.

Mr. E. O. Simcock (Hanley) wrote pointing out
that very few colliery tubs retained their shapes until
they were scrapped. Indeed, there was no assurance
that tubs would retain their shape during their first
working day. The writer had been assured by medical
men that any such lengthy breathing of stonedust would
have a dangerous physiological effect. The best time to
put such a scheme into operation would be when there
were fewest people in the mine. It ought not to require
much ingenuity to invent such a vehicle as would
•perform the work of stonedust distribution when the
coal-drawing shifts were over.

Prof. Louis (Armstrong College) said that Mr.
Halbaum began with six “incontrovertible” proposi-
tions, every one of which could be made the subject of
acute controversy. Mr. Halbaum said that stonedust
must be equally plentiful; the speaker believed that
25 per cent, had been found to be quite sufficient. Mr.
Halbaum said stonedust must be equally finely divided ;
the speaker averred that that was incorrect, and
that the dust must be more finely divided than coal-
dust. Further, with regard to Mr. Halbaum’s clause
(3), the speaker declared there was no inert stonedust
which had a lower specific gravity than had coal dust.
The remaining “incontrovertible” propositions would
certainly be disagreed with by those who were in favour
of the zone system of dusting.

Other speakers remarked that an atmosphere

impregnated with stonedust would be most disagreeable,
even if the dust were free from siliceous particles,
and that distribution of stonedust by hand could
be made even more effective than by Mr. Halbaum’s
method.

Mr. J. B. Atkinson, ex-inspector of mines for the
Newcastle district, asked Mr. Halbaum if he was quite
sure that more dust came from tubs travelling in the
cage in the shaft than from the screens on the surface.
It might be so, but the speaker’s impression was that
where the screens were near the top of the downcast
shafts there was more dust that way.

Prof. Bedson (Armstrong College) reminded those
present that there was a great variety of stonedust. In
all the discussions he had seen in connection with
stonedust the composition of the dust seemed to be put
into the background, although its physical condition
was considered. He had had some experiments made
as to the relative value of gypsum and Chancey’s Mud
(calcium carbide). The latter decomposed, and gave
off carbon dioxide, which aided in the quenching of
flame.

The President remarked that there seemed to be a
tendency on the part of one or two people to throw
stones at the committee at Eskmeals for not getting
everything done that was wanted at once. If they knew
of the work that was being done, they would realise
what a long time it took to make explosions in such a
huge gallery. When one had to deal also with all sorts
of faddists and theorists, it was quite impossible for the
Home Office to please everyone—and he did not think
they were going to try. He did not agree with the
propositions with which Mr. Halbaum had prefaced his
scheme. It was not a question of how the dust was to
be deposited, but of when the dust that had been
deposited should act. It was not absolutely necessary,
for incombustible dust to be able to stop ignition, that
it should be equally plentiful. The stonedust need not
be equally finely divided. He was inclined to think that
the hand method of distribution was, in the end, likely to
prove the best. The physiological action of the dust
was a question of the very greatest importance. So far
they had applied stonedust quietly, and at such times
as would give the least discomfort. In that way they
could work with almost dangerous dusts, and still main-
tain a condition of health. He took a great objection
to the word “ inert.”

Mr. Halbaum said he meant by “ inert ” that it did
not enter into chemical action in the presence of heat.
He further stated that he would defer his reply to the
discussion until he had seen the speaker’s remarks in
print. He did not think that he would have much
difficulty in replying, for it was possible to set off
one objection against another to a considerable extent.
He pointed out that the air current would only lift the
fine dust off the trays and would leave the lumpy
particles on. He could not see how that very fine dust
was going to do any injury to the lungs.

A vote of thanks to Mr. Halbaum was cordially carried.

The following papers were also read:—“Notes on Gob
Fires and Blackdamp, &c.” by Mr. John Morris, and “A
Westphalian By-product Coking Plant which Supplies
Town Gas,” by Mr. Leo Dorey Ford. Reports are
withheld until next week.

Middlesex Foundry Limited.—This private company has
been registered, with a capital of ^5,000 in £1 shares, to
acquire the bu&iness now carried on at Isleworth, Middlesex,
under* the style of Middlesex Foundry Company, and to
carry on the business of metal founders, mechanical engi-
neers, and manufacturers of implements and machinery, &c.,
also to enter into an agreement with R. A. Bryant and T.
Henderson, who are the first directors. Registered office,
The Works, Wor ton-road, Isle worth, Middlesex.

The Institute of Metals.—The annual general meeting of
this institute will be held at the Institution of Mechanical
Engineers, Storey's Gate, Westminster, S.W., on Tuesday
and Wednesday, March 17 and 18, 1914. The meeting will
commence at 3 p.m. on March 17, and 10.30 a.m. on March 18.
The fifth annual dinner of the institute will be held on the
Tuesday at the Criterion Restaurant, Piccadilly Circus, W.
The following is a list of the papers and reports that are
expected to be submitted on March 18 :—First Report to the
Beilby Research Committee, dealing with the solidification of
metals from the liquid state, by C. H. Desch, Ph.D., D Sc.;
“Bronze,” by J. Dewrance; “Vanadium in Brass: The
Effect of Vanadium on the Constitution of Brass containing
50-60 per cent, of Copper,” by R J. Dunn, M.Sc., and
O. F. Hudson, M.Sc.; “The Quantitative Effect of Rapid
Cooling on Binary Alloys ” (second paper),by G. H. Gulliver,
B Sc.; “Crystal P/otomorphs and Amorphous Metal,” by
Prof. A. K. Huntington, A.R S.M.; First Report of the
Nomenclature Committee; “ The I» fluence of Nickel on Some
Copper-Aluminium All ys,” by Prof. A. A. Read, M.Met.,
F.I.C., and R. H. Greaves, M Sc.; “Muntz Metal: The
Correlation of Composition, Structure, Heat Treatment, and
M-chanical Properties, &c., &t,” by J. E. Stead, D Sc.,
D Met., F.R.S., and H. G. A. Sidman, A M.IE.E.; “The
Micro-Chemistry of Corrosion,” Part II., by S. Whyte, B.Sc.,
and C. H. Desch, Ph.D., D.Sc.