February 20, 1914.

THE COLLIERY GUARDIAN.

403

all the bulbs individually through a long-scale ammeter
and use only bulbs of the required efficiency.

In view of the Home Office regulations for the use of
electric hand lamps in coalmines, requiring all lamps to
show a spherical illuminating power of not less than
1 candle power after nine hours’ continuous burning,
it is desirable to instal a photometer of reliable design
and manufacture, and periodically test batches of lamps
for candle power and voltage on closed circuit at the
expiration of an ordinary shift, noting any lamps
showing a diminishing efficiency, to ascertain whether
the bulb of the battery is at fault.

The writer again emphasises that it is only by the
strictest attention to and accurate records of the
details of the daily life of each individual lamp that the
highest commercial efficiency can be secured and main-
tained. The lamp cabin staff should be trained to
observe and note all abnormal conditions that may
occur, and at once apply the remedy, always recording
and reporting the facts to their chargemen, who must
in turn periodically summarise such records in order to
effectually deal with any disputed points that may arise
between inspectors and the colliery management and
the manufacturers of batteries, bulbs, and other integral
parts of the lamp.

Miners’ Electric Lamps and Nystagmus.—The subjact of
electric lamps for miners was discussed at a joint meeting
of the North Stafford Branch of the Colliery Managers'
Association and the Lancashire, Cheshire, and North
Staffordshire Branch of the Association of Mining Elec-
trical Engineers, held at Stoke-on-Trent on Saturday, when
an important statement was made by Dr. T. Lister
Llewellyn on the effect of the use of electric lamps on
the incidence of miner’s nystagmus. A paper was read by
Mr. J. F. Turquand, and in the course of the discussion Dr.
Llewellyn said he wanted to criticise the paper and the
observations of some of the speakers rather severely. The
one object of the electric lamp was to give light, and none
of the speakers had mentioned anything about the candle-
power. The most essential point was the candle-power.
They had heard a lot about safety, and something about
weight. With regard to the latter point, the question of
an extra pound or two was very little to a strong man, and
a collier was as capable of carrying a 51b. lamp as one
weighing 21b. Lamp manufacturers had made a great
mistake in aiming too low—in aiming to produce too small a
candle-power. The Home Office regulations only stipulated
one-candle power, and there were very few lamps capable of
producing one-candle power after nine hours. He had con-
ducted many experiments with electric lamps, and taken
photometric measurements, but personally he had never
found one lamp which produced a candle-power of one after
it had been in use eight hours. He did not say lamps did
not exist which would fulfil this condition, but he had been
unfortunate so far in not discovering one. The average
illumination for the whole of the collier’s working face—
under present conditions with flame safety lamps—was
rather more than one-fiftieth of a foot-candle. The illumi-
nation was very much greater in candle pits. There was
plenty of room for electric lamp manufacturers to produce
a lamp capable of giving more than 1 candle-power, and
it did not matter if the lamp were a little heavier than the
old safety lamp. There was one point he had noticed in the
examination of lamps, and that was that the glass the
manufacturers used was very deficient, and contained
numerous streaks. If they took one of the lamps and held
it so that it threw the light against a purely white surface,
they would find the white surface spotted with marks, show-
ing that a large amount of light had been absorbed. They
needed perfectly transparent glass. Another point was that
the lamp manufacturers should obtain as large an area of
illumination as possible. With a safety lamp the field
of illumination was very restricted. It was important
to get as much light over as large an area as possible.
Further, the more light they could get in an upward
direction, the better it would be for the miner, and he was
glad to see lamps about the table that showed a tendency in
that direction. Some time ago he made some suggestions,
in a book he wrote, for a proposed lamp. He had no inten-
tion of making the lamp himself, but he noticed one or two
points suggested in that book had been carried out by
manufacturers. Probably they would say they had designed
them themselves, but he (Dr. Llewellyn) took credit that
they had copied his suggestions. He had taken a great
deal of interest in the question of illuminating mines, and
he ought not to sit down without saying that in the
improved illumination of mines there was a remedy for the
very distressing disease of miner’s nystagmus. But he
wanted to add a word of warning. This disease was a long
time in the process of making. Very few colliers got the
disease before they had been 20 years underground ; that
was the average. These lamps might be introduced into a
colliery and they would still have cases of nystagmus for a
time—latent cases which would develop in the next few
years. These would occur whether electric lamps were
introduced or not, and therefore colliery managers must not
be disappointed if, for the first few years, after the intro-
duction of these lamps, there were still a few cases of miners’
nystagmus. He hoped, however, with the permanent intro-
duction of these lamps and the miners using them from
their youth up, nystagmus would become almost negligible.

Wet Peat Zones for Arresting Coaldust Explosions.

By R. CREMER.

Periodical watering possesses the disadvantage that
the wetted surfaces dry up rapidly. Further, periodical
and continuous watering affects in most cases the
strata, increasing thereby the danger of falls of roof and
side, and causing a swelling of the floor, whereby in
many cases disturbances in the ventilation (reduction in
the sectional area) and also of the haulage are caused.
With continuously-acting sprayers also the health of
the miners is endangered, as their clothes, when passing
the watering zones, become more or less thoroughly
soaked.

For eliminating the before-mentioned drawbacks of
wet zones the writer has recommended a method of
establishing zones by walls or plates of peat along the
side walls, which are wetted instead of the strata. The
construction of such peat plates is carried out in a
simple way by inserting the ordinary brick-like peat
pieces between wire netting. Hereby handy plates are
formed, which can easily be hung up and removed
along and from the road walls, and of which zones of
any length can be built.

Peat has the ability to absorb water to the extent of
five to six times its own weight, and to retain the same
for a very long period. A square yard of peat plates
absorbs about 10 gallons of water. At a height of the
roads of 2 yards it is therefore possible, when peat
plates of the same height are provided on both side
walls, to accumulate 40 gallons of water per lineal yard,
or 2,000 gallons of water in a peat zone of 50 yards.

5

8

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As the wetted peat liberates the water very slowly,
frequent watering is not necessary. It quite suffices to
sprinkle the peat zones once or twice a week, or, in
cases where there are water pipes in existence in the
roads, to open the valve of a perforated water pipe
provided above and along the zones.

From the arrangement and the capabilities of peat
zones it is evident that they are free from the faults
before referred to. Low in their first cost and their
maintenance, they require only occasional watering,
obviate a contact of water with the strata, and therefore
an increased risk in fall of roof and swelling, and do
not act detrimentally to the health of the men. Apart
from the action of the water suspended in the peat
upon the flame of coaldust explosions, there is another
important factor connected with this system whereby it
is different from other methods, based upon the action of
cooling the flame—namely, the great mechanical effect
which the torn-off and telescoped peat plates exercise
upon flames of explosions, whereby the heat of the flame
is prevented from being transferred into power. This
action is also available aganst consecutiive explosions.

A series of tests have been carried out at the testing
gallery of the Westphalian Mineowners’ Association
at Derne, in January, February, July and September
1913, with the following results :—

Test No. 1.—In the round gallery, 164 ft. from the
cannon, the saturated peat plates were bufit into a zone
of 52J ft. length, covering both sides about 4£ ft. high.
Then light inflammable bituminous coaldust, of sufficient
quantity to produce a thorough explosion, was placed
upon the longitudinal shelves of the gallery. The
depositing of the dust was carried out through the whole
length of the gallery, therefore also beyond the zone as
well as within the zone itself. In the explosion chamber

of the gallery, coaldust was further whirled up. The
ignition in the latter was effected through a shot from
the cannon with a charge of 200 grammes gelatine
dynamite. The explosion of no great force and
travelling with moderate speed, was arrested at about
50 ft. behind the peat zone. The peat plates remained
standing along the wall and were found covered with a
thin layer of coaldust, which was precipitated upon
them and rendered harmless.

Test No. 2.—For the following test the laying of
coaldust was effected in the same manner as before, care
being taken to obtain a more violent and quicker
travelling explosion. In other respects no alterations
were made. The explosion travelled along the gallery
only 197 ft., and therefore was arrested within the zone.
Its duration was one second only. The inspection of
the gallery showed that the peat plates had partly been
torn off the walls and thrown together. Within the
first part of the zone (at 170ft.) they were lodged in a
heap, filling up the sectional area of the gallery, which
from the floor to the roof measures 5 ft. 7 in. up to a
height of 4 ft. 11 in.

Test No. 3.—Without making any alterations in the
peat plates thrown together (by Test No. 2) a further
test was immediately made, in such a way that in the
explosion chamber, the content of which is 529 cubic
feet, a firedamp mixture of 9 per cent, was ignited. The
explosion was arrested also under these conditions,
which presented rather a wet peat dam than a real peat

zone. It forced the heap of peat plates 16 ft. further
towards the end of the gallery. Behind this, at 187 ft.
the explosion flame was no longer observed.

Test No. 4i.—In order to test the effect of the wet
peat zone against an explosion of specially great
violence, coaldust was deposited in large quantity
along the gallery, and a strong firedamp mixture
produced in the explosion chamber, was ignited
by 200 gr. gelatine dynamite. The zone was erected at
the same place and in the same length as before. This
very violent explosion was also arrested by the peat
zone. It extended 216 ft. in the gallery; its duration
was four-fifths of a second. By the force of the explosion
the heavy peat plates, the total weight of which in the
wetted state was 60 cwt., were thrown 52J ft., i.e., the
length of the zone itself, towards the end of the gallery.
They were completely telescoped, and pressed together
in a large heap deposited at 216 ft. of the gallery.
Beyond this heap, which filled the sectional area of the
gallery almost up to the roof, the explosion flame did
not extend.

Test No. 5.—The peat zone, of the same length and in
the same position as with test No. 4, was built of plates
hung up on wire ropes stretched along the sides of the
gallery. The strong coal dust explosion was introduced
by firing an 8’5 per cent, firedamp mixture in the explo-
sion chamber. The phenomena were the same as in
the previous test. The explosion was arrested within
the zone, the peat plates were torn off and thrown
forward up to 65 ft., and the gallery was partly covered
with loose, wet peat.

Test No. 6.—Without making any alterations in the
conditions after test No. 5, fresh coaldust was laid and
methane introduced, which, as usual, was ignited from
the cannon by 200 grammes dynamite, the conditions, as