32

THE COLLIERY GUARDIAN.

January 2, 1914.

In Part II. “Mines and Quarries :
Safety Lamp General "Report and Statistics for
Besearchess 1912,” just issued Mr. Redmayne
has published the results of the
work carried out by Captains Deseorough and
Thomas since the conclusion of the preliminary
•experiments upon which the Safety Lamp Committee
based their Programme of Official Tests.

Before referring to this work in detail, we may
take the opportunity of expressing our gratification
at the earnest way in which the question of the
relative safety of various types of so-called safety
lamps is being investigated. Bor it has for some
time been clearly evident that by no means all of
these lamps are entitled to be considered as fit
for use in a fiery mine. It is, indeed, doubtful
whether the term “ safety ” should not be abolished
once and for all from the literature of colliery
engineering. For it is clear that the degree of
safety which belongs even to the best type of lamp
depends'largely upon the conditions under which it
may be used. And unfortunately the complex con-
ditions under which coalmining is now carried on
possess the inevitable result that the amelioration of
one danger only tends to aggravate another. We
refer especially in this connection to the ventilation
current, which, while contributing to the prevention
of the accumulation of firedamp on the one hand,
adds on the other to the dangers of coal dust explo-
sions and to the possibility of the failure of the
miner’s lamp.

It is satisfactory, therefore, that the Safety Lamp
Committee have fixed the samewhat rigorous con-
dition that miners’ safety lamps must be able to
withstand a current of 1,200 ft. per minute of an
explosive gaseous mixture without allowing the flame
to pass the gauze. This velocity is equivalent to
something over 6 in. per second, and compares
favourably with the higher speeds of the currents
used in the important tests recently carried out at
Frameries by M. E. Lemaire.* But it should not
be overlooked that in the Belgian tests a velocity of
7 m. per second with certain mixtures of gas resulted
in the passage of flame even with double gauze
lamps. It is doubtful, therefore, whether the Home
Office velocity test can be regarded as affording any
considerable margin of safety.

In considering the conditions under which ignition
of firedamp may be caused by safety lamp gauzes,
two factors have to be taken into account. In the
first place the temperature of the gauze may rise to
the ignition temperature of the external gas. This
is clearly dependent upon the velocity of the air
current by which the lamp is fed. In the second
place the pressure of the explosion wave within the
lamp may increase to such a degree that Tame passes
through the gauze and ignites the gas outside. Thus,
danger may arise in two ways—viz., by heating of
the gauze, and by internal pressure within the lamp
—both of which factors may be operative at one and
the same moment.

The Belgian experiments throw light upon the
first of these conditions, and show that when lamp
gauzes reach a temperature of about 1,000 degs.
Cent, ignition of the external gas will generally take
place, and apparently this result follows more readily
with spirit lamps than with oil lamps. It is not
quite clear how far this effect depends upon the mere
contact of the heated gauze with the external air,
and how far it is a result of the passage of flame
through the heated gauze.

With regard to this question of the passage of
flame through gauzes, the Home Office report
contains an account of experiments carried out at
Eskmeals under the direction of Dr. R. V. Wheeler,
in which the internal pressure of an explosion wave,
considering the lamp as a cylindrical tube, has been
studied. This pressure, of course, increases with the
length of the tube—that is to say, with the distance
between the lamp wick and the top of the gauze
chimney. The experiments were carried out in still
air by explosions of either methane or coal gas and air
in cylindrical tubes closed at one end and fitted with
disc gauzes at the other. It would, perhaps, have
been preferable to have fitted cylindrical gauzes in
order to reproduce more nearly the conditions

See Ann. Mines de Belgiqiue, January 18, 1913.

of the majority of safety lamps now in use.
The internal pressure of the explosion wave was
thus alone concerned, without the temperature
factor of the gauzes coming into play. The
results are highly instructive and point to the
conclusion that in double-gauze lamps there should
never be a greater distance than 9 in. between the
wick of a lamp and the top of the gauze chimney.
Another point which is clearly brought out is the
necessity of double gauzes, for with a single gauze
the limiting distance is only 3 in. Again, the two
gauzes must be in absolute contact. If there is an
interspace of only 0’002 in. the above condition of
safety no longer holds. The question arises, there-
fore, whether a single thick gauze would not be as
effective as double thin gauzes. Dr. Wheeler
suggests that this arrangement would to a certain
degree reproduce Davy’s original notion of a bundle
of tubes.

Another point elucidated in Dr. Wheeler’s report
is the difference in behaviour of methane and coal
gas in the experiments. When coal gas and air
were used as the explosive mixture the above limiting
lengths are considerably less, thus emphasising the
fallacy of drawing conclusions as to the behaviour of
safety lamps in a mine when tests are carried out
with coal gas mixtures. The question naturally
arises how far the above results would be influenced
by the substitution of a moving for a still explosive
atmosphere. May we hope for further experiments
upon this point ? Besides the important investigations
of the Explosions Committee the work at the Home
Office lamp testing station has by no means been
barren of important results. In addition to the
results of the tests carried out upon lamps submitted
for approval many constructional points have been
brought to light, and manufacturers will do well to
study the information contained in this section of
the Blue Book, reproduced in another column.

We have always maintained that much of the
comparative immunity from serious colliery accidents
in Belgian coalmines has been achieved by careful
attention to the details of safety lamp construction.
At Frameries much invaluable pioneer work has
been done in this domain of practical mining, and it
is to the initiative thus set up that we owe many of
the improvements of modern safety lamps. What
we are discovering, however, is not so much the
existence of new dangers in the safety lamp as the
power to recognise old dangers too long ignored in
certain types of existing lamps.

Trade Summary.

The London coal trade since the holidays has been very
brisk, The demand for house coal has been unusually
strong and all qualities have quickly responded to the
colder weather. On Monday last public prices were
advanced Is. per ton on all qualities except best coal and
stove coal; these were advanced on Wednesday, best coal
Is. and stove coal 6d. Colliery prices have also advanced
and the pressure for coal on order is very keen. The
limitation of the output during the current week has
compelled many of the London merchants to dip into the
heavy stocks on the ground at the various wharves and
depots. Bakers* nuts are selling freely.

Business has been practically at a standstill on the Tyne
and Wear; steam coals show a tendency to advance.

There is considerable pressure at the moment for
Lancashire house coal. Bunkering requirements are light.
Stocks of slack coal have vanished.

The demand for West Yorkshire house coal has been
greatly accelerated by the cold snap. Supplies of manufac-
turing coal are plentiful. Coke is in rather better request.

In South Yorkshire the steam coal position is easy, but
there is no surplus. House coal is in urgent demand.

Business at Cardiff has been restricted, The output has
been low and tonnage has been delayed owing to stormy
weather. The prospects, however, are very good.

The Scottish coal trade is firm in the absence of actual
business.

THE W4PO1TE TLADE.

The holidays have, as usual, greatly [interfered with
business the last week or so. If anything, we should call
the general tone of the market a shade better, however;
most works are fairly well booked up for a few weeks ahead,
and are standing to their quotations, which may be called:—
Coke tins: I C 14 x 20 (112 sh. 108 lb.), 12s. 9d. per box;
I C 28 x 20 (112 sh. 216 lb.), 25s. 6d. to 25s. 9d. per box;
I C 28 x 20 (56 sh. 108 lb.), 13s. 3d. to 13s. 4|d. per box;
I C 14 x 18| (124 sh. 110 lb.), 13s. 3d. to 13s. 4|d. per box;
I C 14 x 19| (120 sh. 1101b.), 13s. 3d. to 13s. 4|d. per box;
I C 20 x 10 (225 sh. 156 lb.), 18s. 9d. per box; I C squares
and odd sizes, 13s. to 13s. 3d. basis for approved specifi-
cations. Charcoal tins are steady at 14s. 9d. per box
(IC 14 x 20) and upwards according to finish. Coke wasters
are in fair demand, and are quoted :—C W 14 x 20, 12s. 3d.
per box; C W 28 x 20, 24s. 9d. per box; C W 20 x 10, 15s.
per box; C W 14 x 18|, 10s. 9d. per box—all f.o.b. Wales,
less 4 per cent.

THE WELSH CML iffl IR0I TRMES.

Thursday, January 1.

Forth Wate,

Wrexham.

GOAL.

In taking a retrospective view over the past year, it must
be admitted by the colliery proprietors that the character of
the business done has been of a satisfactory nature, both as
regards tonnage and prices. Nor has there been any serious
labour disputes. The demand for house coal has remained
steady throughout the year and there has been little
difficulty in disposing of the output. Even in the summer
buyers were quite ageeable to take spot lots at a slightly-
reduced figure. Prices have been very level for this class
of fuel and are practically the same to-day as they were this
time last year. With reference to coal for gas-making, the
tonnage disposed of from this coalfield has been greater
than it has been for some years, especially with regard to
nuts, the demand for these for gas-making being so great
that there has been but a very small tonnage left for the
open market. The average price obtained for gas contracts
was from Is. to Is. 6d. advance on the previous contract
prices. No doubt an attempt will be made to obtain a
further advance in price when contract time again comes
around, but, as this will not be for a few months yet,
it is perhaps premature to prophesy at the present moment.
The demand for steam coal has been well sustained. Of
course, the bulk is sold to the railway companies for loco-
motive purposes; many of the manufacturing firms, too,
have taken good quantities, as these works appear to have
been kept working regularly thoughout the year. Prices
have also been good, varying from 12s. to 14s. per ton, and
from what can now be seen, the contracts for the coming
year are being fixed up at prices satisfactory to the sellers.
The market for shipment coal has been somewhat variable,
and the total tonnage will scarcely be so great as in former
years. This is accounted for by two factors, one being that
owing to the good demand for steam coal elsewhere there
has not been so much for disposal at shipping prices, which
are generally the lowest; the other being that Liverpool
has had her fair share of labour troubles, especially with the
dockers, causing great inconvenience and delay to vessels,
the result being that many ships were diverted from the
Mersey to other coaling ports, and the North Wales
collieries lost the orders for the fuel required by these ships.
However, at the present there is peace, trade is brisk and
prices are fairly good, ranging from 12s. 3d. to 12s. 9d.
Slack has had its fair share in the market, and for good
rough sorts prices have ranged from 6s. to 9s. per ton
according to quality. A few of the collieries resumed work
on the Saturday after the Christmas holidays, but the
majority did not recommence until Monday, and as generally
happens after a holiday the output was very much reduced
owing to the number of absentees. As New Year’s Day is
always a play day here, the tonnage for the week will be
limited. Current quotations are quoted at the same figures
as last week.	Prices at pit.

	Current	Last week’s
Prices at pit f.o.r. :—	prices.	prices.
Best house coal 		15/6 to 16/9	15/6 to 16/9
Secondary do			14/6 to 15/6	14/6 to 15/6
Steam coal 				12/6 to 13/6	12/6 to 13/6
Gas cbal 		13/ to 13/9	13/ to 13/9
Bunkers		12/3 to 12/6	12/3 to 12/6
Nuts 		11/ to 11/9	11/ to 11/9
Slack		6/6 to 8/6	6/6 to 8/6
Gas coke (at works) 	  Prices landsale:—	13/4 to 15/	13/4 to 15/
Best house coal 		17/6 to 19/2	17/6 to 19/2
Seconds		16/8 to 17/6	16/8 to 17/6
Slack			10/ to 12/6	10/ to 12/6

Newport.

COAL.

For a week past now there has been no fresh business
doing in the coal market. Merchants and salesmen meet
and talk, and a few trifling oddments here and there change
hands, but of real new contracts there has been literally
nothing doing, with the single exclusion of the business
arranged on behalf of the Italian State Railways, who have,
it is understood, placed orders for the supply during 1914 of
about 750 000 tons of Monmouthshire semi-bituminous coal
for locomotive purposes. This amount, which will be fully
equal to about half their total requirements, is stated to be
at a price nearly around 16s. f.o.b., but, as usual with these
buyers, they insist upon secrecy as to particulars being
strictly observed. In the market generally buyers are
holding off, while sellers, confident in a flash of new
business, maintain a firm attitude in their quotations for
all forward business, with a few only coaxing buyers with a
slight concession for the purpose of securing empty wagons
on the spot. Smalls are more plentiful than of late, and a
shade easier, while house coals maintain their position.
Pitwood supplies are ample, good wood now being offered
at 20s. ex-ship. In the freight market holiday conditious
still prevail; what little business being done has shown
shown rates to be quite firm.

Prices f.o.b. cash 30 days, less 2| per cent.

	Current	Last week’s
Steam coals:—•	prices.	prices.
Best Black Vein large ...	17/9 to 18/3	18/6 to 18/9
Wes tern-valleys, ordinary	16/9 to 17/3	17/6 to 17/9
Best Eastern-valleys 		16/3 to 16/9	16/9 to 17/
Secondary do.			15/6 to 16/	16/3 to 16/6
Best small coals 		8/6 to 9/	8/6 to 9/
Secondary do		8/ to 8/6	8/ to 8/3
Inferior	do		7/6 to 8/	7/6 to 7/9
Screenings 		8/9 to 9/	8/9 to 9/
Through coals		13/3 to 13/6	13/6 to 14/
Best washed nuts 		13/9 to 14/3	14/3 to 14/6
Other sorts:—		
Best house coal 		18/ to 19/	18/ to 19/
Secondary do		16/6 to 17/6	17/ to 18/
Patent fuel 		19/6 to 20/6	19/ to 20/
Furnace coke 		19/ to 20/	19/ to 20/
Foundry coke		23/ to 25/	23/ to 25/

most

There are few features of any importance to report in
the local iron and steel trades since the holidays. Buying