March 16, 1917.

THE COLLIERY GUARDIAN.

535

a.c. Generating Set for Sale,
triple expansion, 135 lb., speed 330 revolutions, rope-driven
exciter.—HELLE WELL & CO., Royal Exchange, Manchester.

SEMI-PORTABLE AND PORTABLE ENGINES.

pv/Vn.h.p. Compound Undertype Semi-

O' \J Portable Engine, by Robey, h.p. cylinder 13^ in., l.p. cylinder
23 in.j stroke 24in., 140 lb. w.p., a very fine engine; £725.

Two 12-h.p. Semi portable Engines, by Robey, 120 lb. w.p.; £170 each.

10-h.p. Marshall Portable Engine, single cylinder, 80 lb. w.p.; £130.

8-h.p. Portable Engine, by Ruston Proctor, 100 lb. w.p.; £120.

JOHN FRHDK. WAKE, DARLINGTON.

Wanted.—Lancashire Boiler, 30 ft.

by 8 ft., 120 lb. pressure, hand-fired.

SILVERDALE CO. LTD., Silverdale, Staffs.

For Disposal, Two Steel Shafts, 20 ft.

6% in. over.all length, and 12 in. dia. at centre and 8%in. at ends; also
one Double Arm Belt FLYWHEEL (in halves), 15ft. dia. and 2 ft. lOgin.
width of face; and one ditto wheel 5 ft. dia. and 2 ft. 10J in. width.—Boz 6701,
Collierv Guardian Office, 30 & 31, Furnival- st., Holborn, London. E.C. 4.

TXT’anted.—Boiler Tanks, or old Boilers

V V for making into tanks.

A. UNDERWOOD, 3, Queen-street, E.C.

HAULING OR WINDING ENGINES.

Pair very fine Hauling or Winding

Engines, by Grange Iron Co., 16 in. cylinders with Corliss valves,
almost as new; £250.

Pair 16 in. cylinder link-reversing engines, suitable for hauling or winding;
£150.

Pair of 13 in. Engines, reversing, by Marshalls, suitable for hauling or
winding; £180.

JOHN FREDK. WAKE, DARLINGTON.

For Sale.—2 Galloways, 5 Flue Lanca-

SHIRE BOILERS. 120 lb. pressure, 30 ft.* by 8 ft. 6 in. dia.; also
several old EGG-END BOILERS, suitable for tanks.

SILVERDALE CO. LTD., Silverdale, Staffs.

For Sale.—126-kw. Steam Generating

SET, 220 volte, 6-pole, by Mather & Platt.

A. UNDERWOOD, 3, Queen-street, E.C.

Generating Set for Sale.

\ J d.c. 500-550 volts, 135 lb., speed 240, compound engine.

HELLE WELL & OO., Royal Exchange, Manchester.

STEAM NAVVIES.

Q-ton Whittaker Crane Type Navvy,
fl 4 ft. 8i in. and broad gauges, modern first-class machine; £1,100.
10-ton Wilson Crane Type Steam Navvy, good condition; £950.

10 h.p. Ruston Proctor Steam Navvy, late type; £750

10-ton Whittaker Crane Type Steam Navvy, excellent machine; £850.

JOHN FREDK. WAKE, DARLINGTON.

J. W. BAIRD AND COMPANY.

PITWOOD IMPORTERS,

WEST HARTLEPOOL,

YEARLY CONTRACTS ENTERED INTO WITH COLLIERIES.

OSBECK & COMPANY LIMITED,
PIT-TIMBER MERCHANTS,
NEWOASTLE-ON-TYNE.

SUPPLY ALL KINDS OF COLLIERY TIMBER.

Telegrams—“ Osbecks, Newcastle-on-Tyne.”

**♦ For other Miscellaneous Advertisements see Last
White Page.

AND

Jsisraal of th® Coal and Iron Tradas.

Joint Editors—

J. V. ELSDEN, D.Sc. (Lond.), F.G.S.
HUBERT GREENWELL, F.S.S., Assoc.M.I.M.E.

(At present on Active Service).

LONDON, FRIDAY, MARCH 16, 1917.

The London market continues brisk. Public
orders are not so pressing, and merchants are over-
taking arrears. Supplies are still short.

The general tone of the Tyne and Wear market is
better, although spot business is still possible at
slightly lower prices. Coke is very firm. Quotations
in Lancashire are practically unchanged, but they
are nominal for the most part. For good rough
slack 17s. has been paid. The supply of Lancashire
steam coal is particularly small. Yorkshire collieries
appear to be suffering mainly from wages shortage,
and similar trouble affects the supplies in the
Midlands. Heavy stocks in South Wales have
caused quotations to weaken. A fair amount of
business in Scotland is reported, despite the
shrinkage in exports.

Chartering is still checked by the inadequate
tonnage supply. Coke rates from north-east ports
to north French ports are 47s. to 52s. 6d. The
business in Cardiff improved a little in the middle of
the week, but the position is still very unsatisfactory.

The Inter-Allied Chartering Executive in London
has been given discretionary power to go outside the
schedule of rates in order to obtain neutral tonnage.

The Controller of Coal Mines has addressed a
special note to coal owners, factors and merchants,
in which he asks them to refrain from making
forward contracts for longer periods than three
months.

The issue of the Board of Trade returns relating
to coal has been suspended for the present.

So far as information is available,
Coal Dust the United States was the only
Experiments country in which, systematic coal
in U.S.A, dust experiments were pushed last
year to any conclusive results. These
have recently been, embodied in a report by the
Bureau of Mines. They represent the continuance
under mine conditions of tests originally made in
the Pittsburg experimental gallery in 1909, and
later in the experimental mine. All these tests
give valuable if not unexpected results; for,
even if they are merely confirmatory, it is impossible
to have too much proof of the validity of the
conclusions to which they point. The experiments
cover all the known factors bearing upon the
question of stone-dusting as a preventive of coal
dust explosions. We say the known factors advisedly,
for there can be no certainty that there are not still
some physical conditions, not yet appreciated, which
may exert a not unimportant influence upon the result.
To some of these more obscure features we shall
refer in due course. The main interest of these
tests, as additions to previous knowledge, lies in the
fact that they were carried out as near to practical
working conditions as it seems to be possible to
devise; and, if for no other reason, they are, on this
account alone, deserving of close attention.

With regard to the influence of the size of the
coal dust particles, the importance was established of
ascertaining for every mine the size of the dust
present as well as the quantity per unit area. For
this purpose systematic sampling of all dust found
on roadways, roof and timbers, with corresponding
screening tests, is recommended. The significance
of this precaution is indicated by the fact, revealed
by the tests, that only the comparatively coarser coal
dusts were rendered non-explosive by a 50 per cent,
admixture of shale dust, the natural coal dust
requiring 75 per cent, of shale dust for a similar
immunity. With regard to the amount of dust
per unit of area or volume that would set up
explosible conditions, it was found that for pro-
portions exceeding 1 lb. per foot (0-275 oz. per cu. ft.)
the explosibility was practically constant. The
minimum proportion of coal dust required for the
propagation of an explosion with pure pulverised Pitts-
burg coal was found to be rather larger than that
determined in the gallery tests, both at Pittsburg and
Lievin, but was still so small as to be barely appre-
ciable in a ordinary unlined mine passage. Neither
was there any ground for concluding that there
would ever be, under normal conditions, too much
coal dust present. Thus there would seem to be no
practical importance in regard to the maximum
limit; while the minimum limit is surprisingly low
for certain classes of coal. The inference is that the
current conception of a dusty mine may need some
revision.

This brings us to the next question, the composi-
tion of the coal. Upon this point the Bureau of
Mines only affords general information, the detailed
results being promised at a later date. So far as
conclusions have yet been drawn, they confirm the
generally accepted view that, while coal dusts showing
high ash, or high moisture content, require smaller
proportions of shale dust to render them inexplosive,
the reverse is the case with volatile matters. It is
interesting to find that propagation of an explosion
was obtained in the mine in a dripping wet con-
dition. In one case a mixture of 77 per cent, of
pulverised coal with 23 per cent, of added water gave
a strong propagation; but in the presence of 10 per
cent, of water a mixture of 40 per cent, of coal dust
and 50 per cent, of shale dust was found to be
incapable of transmitting the explosion wave. Since
the same coal dust without water required 75 per
cent, of shale dust to render it innocuous, we may
conclude that, under the conditions of the experi-
ment, 10 per cent, of water would be the equivalent,
in retardation effect, of 25 per cent, of shale dust. It
is, however, obviously impossible to fix such equiva-
lent valued with any approach to accuracy. Precisely
the same comment may be made with regard to the
effect of inflammable gas on the ignition of coal dust
and the propagation of an explosion. Experiments
were made with proportions of 1, 2 and 3 per cent, of
gas in the air current, and the average result is

expressed in the statement that 1 per cent, of natural
gas will offset from 5 to 10 per cent, of shale dust.
It -would, however, be highly speculative to infer
that there is any linear relation between gas and
stone dust which would enable safe limits in the
proportion of stone dust to be accurately fixed in
fiery mines. This branch of the investigation needs
much further elucidation. The Bureau of Mines
tests go to show that the presence of gas has more
effect in increasing the explosibility of coal dust in
proportion as the latter approximates to the character
of anthracite. If this conclusion is borne out, the
immunity of certain coal mines from dust explosions
may be found to rest upon a very slender founda-
tion.

Another factor which has rightly been credited
with no small importance in connection with colliery
explosions is the shape of the space in which the
explosion wave is propagated. It has been assumed
that dust explosions are more readily brought about in
narrow galleries than in wide rooms. The experiments
upon this question seem to be somewhat inconclusive,
and it is to be hoped that they will be carried still
further. To all appearances, if the conditions are
favourable, there is no limit to the apparent vagaries
of explosion wave propagation when once it has
been started upon its course.

Finally, let us again utter a word of caution
respecting the possibility of arriving at complete
immunity from coal dust explosions in the future,
that is to say, under practicable, or rather economic,
conditions of working. That a very large degree of
safety will be secured there is no doubt, and we trust
the evil day may be long deferred when some
strange and unaccountable occurrence may tend to
shatter our faith in the efficacy of human effort in
the face of the unknown.

The address given by Mr. F. Dudley

The Docker at the first general meeting
Federation of the Federation of British Indus-
Of British tries will receive all the more atten-
Industries. tion on account of the criticisms
which have been recently offered as
to the somewhat nebulous policy of this newly
formed body. The president gave what seems to be
a wholly reasonable explanation of this attitude.
He showed that the Federation is engaged upon a
great experiment, upon which the future prosperity
of the country may depend. Granting this premiss,
it must be allowed to develop in the natural way
like any other scientific experiment, by the method
of trial and error. In the president’s own words, to
adopt an immutable form of constitution would
involve the loss of the chance of learning from
the mistakes which are almost certain to be made in
so novel an adventure—novel, that is, in this country,
where industries have been left so entirely to indi*
vidual enterprise, and where many of our leading
manufacturers are still somewhat chary of accepting
the principle of association and all that this term
implies. The case could have been put even stronger.
To have formulated a more definite programme at
this stage would have been a fundamental error from
which it would have been difficult to recover. We
imagine that no small part of the criticism that has
been forthcoming has been due to some amount of
impatience and the desire to push forward certain
views which, rightly or wrongly, are very strongly
held by many British manufacturers. But with all
deference to such opinions, it may be quite fairly
argued that the soundness of these views is not to
be demonstrated by mere dogmatic assertion. If
the experiment which the Federation is now carrying
out is rightly conducted, the true path of progress
will emerge of its own accord, and with a clearness
that cannot fail to carry conviction. Mr. Docker
says, in fact, let us first get together as a truly
national federation, embracing all the manufacturing
interests of the country, and not as a party united
by a particular programme.

This does not imply that the Federation has no
programme. One of its principal objects is to render
articulate the present disjointed elements of which
our industrial system consists. It aims at the
unification of industrial interests so as to command
the attention of the Government when framing