716

THE COLLIERY GUARDIAN.

October 2 1914

main bunkers or, where required on the deck, to be
carried, as shown, to positions otherwise inaccessible.

We may next consider the question of coaling whilst
under way at sea. The collier or transport is towed
by the battleship, and between the foremast of the
former and the main mast of the latter a cable is rigged,
on which is hauled a travelling carriage, The coal is
filled on the collier or transport into bag'., which are
hoisted to the masthead, and there attached to the
carriage ; a rope is connected to the carriage for hoisting
to and from the battleship by means of winches, the
bags being deposited on the deck. The essential
feature to coal at s^a in this manner is that the cable
must be kept at a regular tension, and sufficient to
withstand the weight of the travelling cariiage when
loaded, irrespective of the variation in distance between
the battleship and the accompanying collier. This is
accomplished by means of a compensating arrangement
of the special winches whereby the cable is automatically
hauled in or paid out. The towing hawsers provide
for an ave 'age distance of about 400 ft. between the
battleship and the collier, and it is practicable to
transfer coal in J to 1 ton loads at the rate of fiom
40 to 60 tons per hour whilst steaming at a speed of
10 to 12 knots; the equipment can be rigged within
about 20 minutes and stowed away in even less time.

Coaling while steaming thus provides for the greatest
mobility of a fleet, and enables its ships to be ah-rt and
ready for action, the colliers obtaining the supplies from
the nearest coaling station or port. The equipment can
be carried either by a collier or by a battleship ; in the
latter case, it is possible for supplies to be obtained not
only from a special collier, but from any class of vessel
chartered for carrying coal, or from a naval cruiser,
merchant ship, &c. It may here be mentioned that
after a naval war—only a few years back—the lack of
the fleet’s effect was attributed to the absence, at a

I

,r?'

Fig. 3.—Battleship Coaling under Steam.

critical time, of several of the ships for the purpose of
coaling.

Having referred to colliers, and coaling battleships
therefrom either whilst at anchor and when steaming
at sea, mention should now be made of storage depots.
Floating depots have been adopted in some ports for
the storage of 10,000 to 12,000 tons, in addition to the
shore storage; such an arrangement allows of battleships,
&c., receiving large supplies, in a short time in cases
where a sufficient depth of water is not always available
alongside the quays or where the quay space is limited.
A floating depot is spec:ally constructed either for
delivery in bulk by grabs or for sacking automatically
direct from hopper shoots. As regards shore storage,
battleships in some cases go alongside to be supplied
direct, or barges are loaded with coal in bags and towed
to the ships, where it is hoisted on board; or, further,
floating craft, mechanically equipped, are sometimes
adopted, which are loaded with from 500 to 1,000 tons
of coal and are propelled or towed from the shore to the
ship, where the coal is delivered mechanically by grabs,
self-discharging buckets or conveyor shoots. The craft
may in addition be utilised for ti ansferring coal rapidly,
from a vessel which is not specially equipped, to a
battleship, the coaling craft lying in between the two.

Several nations have considered it desirable to main-
tain coal supplies for naval requirements not only at
their naval bases, but at coaling stations, whilst at other
less prominent ports arrangements are made for a
minimum storage to be kept by a contractor. Greatest
attention to the importance of coal supplies for naval
requirements has doubtless been given by England and
the United States Governments, which has led to the
establishment of numerous coaling stations. The
equipment of the more recent and important of these
stations has provided for discharging at wharf or rail
and transferring to storage, taking from storage and
delivery to warships, colliers or barges either in bulk, or
filled in bags or baskets ; also changing coal in storage
to prevent excessive deterioration. The last-mentioned
has led to the introduction of methods to prevent
spontaneous combustion and arrangements of storage
under water.

A Comparison of Electric and Oil Safety Lamps.

Safety, Efficiency, and Cost.

A meeting of the Midland Institute of Mining, Civil,
and Mechanical Engineers was held at the University,
Leeds, on September 29. Mr. Walter Hargreaves
occupied the chair, and those present included Prof. N.
Robiette, of the Universite du Travail, Belgium, who
assisted Prof. Lemaire, of Louvain, in conducting
experiments at Frameries relative to the explosibility
of various types of mining lamps.

Mr. E. A. Hailwood, M.I.M.E. (managing director
of Messrs. Ackroyd and Best Limited, safety lamp
makers, Morley, near Leeds) read a paper on “ Electric
Miners’ Lamps Compared with the Combustion Tube
Oil Lamp.” Mr. Hailwood quoted the report of the
Chief Inspector of Mines on the explosion at the White-
haven Colliery in 1910, and observed that this appeared
to be about the first serious occasion when electric
lamps were definitely officially recommended for use in
coal mines in Great Britain. Since the date of this
suggestion and the publication of the conclusions arrived
at by the Chief Inspector, the Government of Great
Britain had established a lamp testing station, and the
writer felt that the knowledge gained by the Govern-
ment officials was such that their eyes had been opened
to the extraordinary “ safety margin ” possessed by
miners’ safety lamps, as even fairly well constructed
safety lamps easily passed the severe test set up by the
Government, and it was noticeable that at recent
enquiries following explosions the Government official:;
had not been so prone to blame the safety lamp.

It might not be out of place to put on record some experi-
ments which he had carried out on some of the actual safety
oil lamps recovered from the Whitehaven coal mine, and
also on up-.to-date electric lamps, and to consider whether
the fears in regard to flame safety lamps were well grounded,
whether it was necessary to reject flame lamps in favour of
electric lamps, and whether the anticipated benefits from
electric lamps were likely to be realised. Also to consider
a substitute for the electric lamp, which, whilst retaining
all the good features of the flame safety lamp, possessed
additional ones,, and, at the same time, gave an illumination
superior to that of the electric lamp. The lamp which he
was referring,to was that known as the Hailwood combustion
tube flame safety lamp.

Experiments with Electric Lamps.

It used to be, and was now by many people, thought to
be impossible to create an ignition of gas by the breaking
of a small bulb of an electric lamp. To refute this he pro-
posed to demonstrate to the meeting that it was not a diffi-
cult matter to accomplish. He would place a small portable
electric miners’ lamp in the chamber of the Hailwood lamp-
testing machine No. 2, and surround the lamp by an explo-
sive mixture of coal gas, air, and coal dust. He would then
strike the lamp glass and bulb with a pick-pointed chisel,
and it would be noted that he easily created an explosion
by the breaking of the electric bulb. In the apparatus
shown he had secured hundreds of ignitions of gas by the
breaking of the electric bulb. The several experiments
carried out quite recently had resulted as shown in Table A.

He had not been able to carry out further experiments
upon the Ceag and Oldham lamps owing to lack of samples,
but, judging by the experiments on the firm’s own electric
lamp, there did not appear to be any reason to suppose’ that
these lamps would give any different results, the funda-
mental principles and behaviour-of all the portable electric
lamps being very similar. The coal gas used in the experi-
ments described in this paper was Morley Town gas, the
coal dust was the common engine coal dust from the York-
shire Iron and Coal Company’s Tingley pits, and was ground
in an ordinary chemist’s mortar.

He understood that a serious explosion which occurred at
the mine, “ La Haye,” at Anderhies, Belgium, was caused
by an electric lamp. From the foregoing experiments it
would be seen that various makes of electric lamps appeared
to be capable of creating violent explosions, not only in high
and rich percentages of gas, but also in very low percentages.

Table A.

Hailwood’s	Per-	Coal dust	Voltage		
experiment.	centage	240 mesh,	Amperes	of cell,	Result.
Electric lamp of coal No. 2123. gas.*		quantity by of bulb, fluid measure.		closed circuit.	
1. 2123 .	.. 7 ..	1 OZ.	.. 0'8 ..	. 1-88+..	Ignition.X
2. Do.	. 6 ..	do.	.. do. ...	do. ...	Ignition.
3. Do. ..	. 5	do.	.. do. ...	do. ...	Ignition.
4. Do.	. 4 ..	do.	.. do. ...	do. ...	No ignition.
5. Do.	. G ..	. 1 oz. 240	.. 1'0 ...	do. ...	Ignition.

mesh and
1 oz. 90 mesh

6.	Do. ...	41 ...	do.	... do. .	.. do. .	.. Ignition.
7.	Do. ...	41 ...	do.	... do. .	.. do .	.. No ignition.
8.	Ceag ... electric lamp	14 ...	do.	... 0-8 .	.. 2'0 .	.. Very violent explosion.
9.	Ceag ... lamp	8 ...	do.	... do. .	.. 2'08 .	.. No explosion.§
10.	Oldham 14 ... lampH		do.	... do. .	.. 2'0 .	.. Very violent explosion.

* After allowing for an average oi 7 per cent, non-combustibles— i.e.,
the percentages stated are the actual average per cent, qf combustibles
in the gas.

t Almost run down.

t Filament aglow for a few seconds after explosion. Very bright just
at moment of extinction of filament.

§ Filament aglow for 20 seconds after bulb burst.

|j Very thick outer glass ; |in. thick walls.

In experiment No. 6, when 4J per cent, of gas with coal
dust was ignited, it was very disquieting to find that in the
same machine containing exactly the same percentage of
gas and coal dust, that on passing a lighted taper into the
chamber and waving the same about, the mixture did not
ignite. The explanation appeared to lie in the fact that
the filament of an electric lamp burned in a vacuum, and,
upon the bursting of the bulb there was an instant rush and
probable momentary compression of the gas mixture in the
vicinity of the filament, which gas mixture, on coming into
contact with the red-hot filament, ignited and. set up a per-
cussive sort of explosion that caused a shock amongst the
molecules of the surrounding gas, and thereby created an
ignition in a mixture which would not otherwise be ignited.
The earliest forms of electric lamps had a very thin outer
glass. Some years ago, in an endeavour to prevent the
ignition of gas by a filament, he surrounded the bulb with
water. This was unsatisfactory, and when oil was tried it
was found to be no more satisfactory. It had been suggested
that a fuse inserted in the electric circuit. would prevent an

ignition of gas. He doubted very much, however, whether
this would be so, as the fuse would have to be capable of
carrying sufficient current to incandesce normally the fila-
ment. That necessitated a very delicate measure of current;
even a slight crippling of the current would have a marked
effect on the candle power of the lamps, and such a device
would also constantly be out of order. When used for mines
he did not think the fuse system practicable fer the object
in view.

Heating Experiments on Oil Lamps.

When a ready-lit flame safety lamp, such as those used in
the Whitehaven mine, was subjected to a sudden rush at
great velocity of explosive gas or of air, it was usually
instantly extinguished. With regard to the Whitehaven
lamps, which were subjected to Hailwood's drop test (repre-
senting a fall of roof) the lamps after being alight for half
an hour so as to get quite warm, were placed in the
chamber and explosive mixtures of gas and air produced, into
which fine coal dust was mixed. A weight of 51 cwt. was
then dropped upon the lamps, but no ignition of the gas
mixture ensued in any of the tests. In the case of three
Whitehaven lamps from the same group which were passed
ready lit into a slightly modified form of apparatus, con-
taining mixtures of coal gas and air, and kept in the chamber
for 10 minutes each, no ignition of the surrounding gas
occurred. Coal dust was injected in the atmosphere by
means of a rubber bulb, and was kept well on the move by

means of the constant operation of the large flap fan inside
the apparatus, while the lamps were well bumped and swung
about in the mixture during the tests. No ignition of the

outside gas occurred. Six of the lamps were then tested in
the apparatus in a compressed gas mixture. From readings
obtained and the noise created by the explosions, there was
no doubt that the mixture was of an extraordinarily powerful
nature and the resistance offered to the passage of flame by
the rusty gauzes of the Whitehaven lamps in the tests in
question was highly satisfactory. During the official enquiry
Prof. Thompson, of Leeds University, tested similar-lamps
(recovered from the mine) in explosive gaseous mixtures at
velocities up to 1,260 ft. per minute, and got no outside
ignition.

In schools it was taught, and generally accepted, that
when “ gauze ” was red-hot it would pass flame and ignite
any surrounding gas. To prove that assertion it had been
the practice to place a disc or gauze web over a Bunsen
burner, get the gauze red-hot, and ignite the gas through the
same. In experimenting with this system he had observed
that if the Bunsen and gauze disc were surrounded by ordinary
air it was easy to get the gauze web white-hot, and in this
condition surplus gas passing from the Bunsen would go
through the white-hot gauze and ignite on the exterior
thereof, this ignited gas apparently being surplus gas over
and above that required to redden the gauzes. It was
important to observe that in this experiment the gas passed
from the underside of the gauze or from the inside to the
outside of the gauze, whereas in the miners’ lamp the gas
would pass from the outside to the inside of the lamp, a
most important difference.

In a miner's oil safety lamp there was practically no gas
generated inside' the lamp and gauze,, and so from this
source the temperature of the gauze could not be raised to
anything like red heat, the oil flame being too far away to
do so unaided by gas. Consequently, there would be no
surplus gas inside the lamp to ignite as it passed out. He
had found out that if the Bunsen and gauze be completely
surrounded by a mixture of coal gas and air (instead of air
only), though the gas cock of the Bunsen burner remained
open (to exactly the same extent as it was to enable suffi-
cient gas to pass to make the gauze web white-hot, and to
pass flame through it when in air) that when surrounded
by gas mixture the gauze could not be heated to white-hot
point, but that it immediately became “ dull,” just as
though the flame inside the gauze when also fed with gas
from the outside of the gauze, either stifled for want of
oxygen, or was covered with a mantle of carbonic acid gas.
which deadened the flame and prevented the gauze getting
very hot. To demonstrate this he would take a gas-fed
Bunsen burner covered with a Davy gauze. It would be