June 15, 1917.

THE COLLIERY GUARDIAN.

1127

fairly high velocity, there is little opportunity for any
deposit to form and eventually block the pipes. An
8 in. pipe for use on the surface to the borehole, and a
6 in. pipe inside, will give good service.

Before commencing to run slush, it is necessary to
pump water for, say, half an hour, and after finishing the
run of slush it is necessary to pump water again—finally
draining off the pipes before stopping work. If those
precautions were adopted, slush might be run for months
without any delays due to the pipes becoming blocked.

In filling an area, in order to form a solid barrier
which will prevent a squeeze, it is necessary to make a
large barrier pillar, say 500 ft. wide, so that there is no
chance for the squeeze to override the pillar. The
general method of slushing may, therefore, be summed
up as follows :—The slushing material is first of all run
through a crusher, then mixed with water and pumped
by a surface pump to a tank located over a borehole.
The slush runs down the borehole, and is conveyed
inside to whatever part of the mine is being slushed.
With a borehole 400 ft. deep it is possible to run slush
2,000 ft. inside the mine, including any slight up-grades
such as rolls. A bed 15 ft. thick may be strengthened,
by slushing, in the following manner, so as to prevent
any possibility of a squeeze. The slope pillar was first
strengthened and made 500 ft. wide. As the thickest
coal was on the west side, a barrier pillar 600 ft. wide
was put in by filling the chamber with slush. It was
then possible to start robbing from the western
extremity, the slushed area effectually preventing any
squeeze from spreading. It is not possible to lay down
any hard-and-fast rules to cover all cases, as much
depends on local conditions, character of the roof, &c.,
and the method of procedure just described is only
one way of many which could be adopted.

Finally in building batteries to retain the slush, it
must be remembered that the most effective battery is
one which allows the water to drain off, and so prevents
the accumulation of any pressure due to a hydrostatic
head. In some instances, old burlap, held in place by
wires strung on props, has made effective batteries, and
in all cases the principle of allowing the water to drain
off and only retain the solid matter must be carefully
observed.

Where the Mammoth coal bed is over 40 ft. thick
and is mined as a pitching bed, there have been instances
of the use of timber which were probably without
parallel in the history of mining the world over. The
Mammoth bed, in some cases, folds, until at the widest
part of the convolution there is a total thickness of
from 200 to 300 ft. Several years ago, gangways were
driven in the centre of that body of coal, with the result
that, after trying for years at great cost to keep such
gangways open, the expense finally became prohibitive,
and they had to be abandoned. Even where the bed was
60 ft. thick, in some cases as many as 12 squads of men
(12 miners and 12 labourers) were required to keep open
one gangway less than 4,000 ft. long. The modern
tendency has been to replace gangways in the Mammoth
bed, wherever possible, by driving passages in thinner
underlying beds, and where such gangways must be
driven and kept open for a period of years, to put in
some permanent type of timbering, such as steel. To
give some idea of how these old timbered gangways
were on the move, it had been estimated that 52 ft. of
bottom were taken up in one gangway over a period of
12 years—i.e., every three months the bottom heaved
over 1 ft. The feature which stood out with greatest
prominence in that work was that, heavy timber being
considered necessary to maintain such gangways, timber
24 and even 36 in. in diameter was employed.

In order, therefore, to avoid the expensive upkeep of
Mammoth bed gangways as main haulage ways, the
general method is to drive these passages in the
Skidmore or some other underlying bed. In some
cases, however, a gangway in an overlying bed, such as
the Primrose, is used as a main haulage way.

'With regard to the way the pressure and general
squeeze are brought on gangways in the Mammoth
bed—especially when a breast started near the bottom
of the lift—under average conditions, where the bed is
30 to 60 ft. thick, when the breast had been run empty,
and the pillars cut, the greatest amount of coal had been
extracted near the bottom of the lift, and consequently
the ground tended to break where the resistance was
least. The ground is often not able to break with a
clean fracture and so relieve the pressure ; consequently
a squeeze is thrown on the airway and gangway, which
had a continuous action, causing the floor of the gangway
to heave and the timber to break as fast as it was put in,
while the maintenance of the airway was difficult. The
next step was to drive a gangway in the Skidmore bed and
start the breasts at the bottom of the lift at a point near
the top of the rock chute. That, however, did not solve
the problem of mining the coal near the top of the lift,
so in order to get a good extraction it was necessary to
drive a slant chute in the Skidmore bed, and put through
a second rock hole for the purpose of winning the top
coal. As the top coal had been partly worked, and had
to be re-mined by means of chutes, that method was not
satisfactory, owing partly to the amount of timber used
in the chutes and partly to the crushed condition of the
coal recovered. The method finally adopted where the
bed was virgin, was that the upper half of the lift was
mined first by the breast method, and then after the
pillars in the upper half had been robbed, the lower
half was worked in the same way. Thus, the whole
lift was mined out with a minimum use of timber, a
maximum extraction and a high percentage of prepared
sizes. In timbering gangways in the Mammoth bed,
where the ground is at all soft or liable to run, fore-
poling is resorted to. When driving in solid ground the
miner generally excavates ahead, and then places the
poles in position so as to prevent a fall or rush of coal.
When driving through a fall or broken ground, how-
ever, it is necessary to use poles 16 to 18 ft. long, and
drive them ahead, using a force of men and a heavy
ram. In work of that character it takes expert men
three shifts to put up one set of timber, and miners
who are not accustomed to the work may not get one
set up in a week, with little chance of getting through
an extensive fall, except at enormous expense.

In addition to poles, lagging and slivers are employed.
In some cases where the ground is very soft and dry, a
hole the size of a man’s hand will allow enough coal to
run through to fill the gangway. Instances of that
kind, while not the rule, are by no means uncommon,
and invariably in gangways in the Mammoth bed poles
and lagging are used. In making a chute in the
Mammoth bed through soft ground, poles and fore-
poling must be resorted to; it being necessary where
the ground is bad to drive forepoles ahead as in the
gangway, and in some cases it is necessary also to fore-
pole on the sides of the chute.. The chute is driven
with a travelling-way on one side, which is also used for
carrying up planks and timber. The manway or
travelling-way is kept separate from the coal side by
putting up a centre prop to which planks are nailed as
a general rule, and the bottom of the coal chute is then
covered with sheet iron. Sometimes the pitch is made
heavy enough so that the sheet iron is not needed.

For the purposes of ventilation in driving chutes, a
line of ventilasing or air pipe is run up the manway
side 8 by 10 in. (inside measurements) and connected to
a fan suitably located.

Very difficult ground can be traversed by chutes of
that description when experienced men are employed.
When re-opening ground which has already been mined,
soft spots and caved ground, which consist entirely of
large rocks, can be successfully passed in order to reach
coal which seems to be inaccessible. Other pitching beds
such as the Orchard, Primrose and Buck Mountain, are
timbered after the same style as the Mammoth, but
lighter timber can be employed, it being possible to use
10 in. sticks for legs in many cases. In fact, the general
tendency during the past few years has been to decrease
the size of gangway timber in all beds.

The Decay off Mine Timber,

It has been estimated by authorities on this subject
that 50 per cent, of the wastage of timber in the mines
of the United States is due to decay and insects, the
greater proportion being due to decay. Many methods
have been tried to preserve mine timbers, the most
typical being : (1) Seasoning, (2) carbonising or burning
the outside, (3) painting, (4) immersion in a hot tank of
antiseptic solution, (5) impregnation with creosote or
other substance under pressure. Of all these methods
painting, immersion or impregnating with creosote is
the most satisfactory, but in mines where the fire risk
is great that cannot be recommended. Iron sulphate,
copper sulphate, and zinc chloride have been used for
antiseptic solutions, the strengths being approximately
5 per cent, iron sulphate, 10 per cent, copper sulphate,
and 10 per cent, zinc chloride. The usual time of
immersion is 12 hours. Where mining conditions are
such that timber rots rapidly, it pays to put in steel
timbers, unless market conditions make the price of
steel prohibitive.

IKDIM MD COLONIAL 1WTES.

Africa.

South African Coal Trade—The opening of the year wit-
nessed a marked improvement in the coal trade of the
Transvaal and Natal provinces, and these provinces to-day
produce seven-eighths of the total coal output of South
Africa. According to the returns of the Mines Depart-
ment, the pit top average selling price of the Transvaal
collieries increased from 4s. 7d. per ton in December, to
4s. lOd. per ton in January; whilst in Natal the price
increased from 7s. 4d. to 9s. lOd. per ton. This improve-
ment is due to the coming into operation of new contracts
at the beginning of the year, and for some time past it
has been rumoured that the Natal collieries intended
putting up the price of bunker coal to 10s. per ton at the
pit for all new contracts. When the railway suddenly,
without notice, advanced the railage rate to the different
ports by 6s. per ton, without in any way affecting the
demand for bunker coal, it was evident that the collieries
would be justified in following suit, as whatever justifica-
tion there may be in the railways advancing. the railway
rate, there was more on the side of the collieries in asking
for a higher price for coal all round.

Coal Prices in the Transvaal.—The total amount of coal
sold in the Transvaal during January was 535,480 tons,
as compared with 545,945 tons in December, so that it was
not to any marked increase in the demand that the rise in
prices was due, but to the determination of the Coal
Owners’ Association to obtain a better price. Selling
prices of coal in the Transvaal have been for about five
years in the neighbourhood of 4s. 4d. . per ton on the
average at the pit tops, and only in India and Japan has
any quantity been sold at such a low price.at the pit tops ;
and with the advancing prices of explosives and stores,
and the chronic scarcity of railway trucks, the collieries
of late have made but little profit. The 17 collieries in
the Middelburg district sold 406,778 tons in January, as
against 424,428 tons in December; but the average pit top
selling price increased from 4s. 8d. to 4s. lid. per ton. The
Springs Brakpan area sales only increased from 47,368 tons
to 48,983 tons, whilst the average selling price only
advanced from 4s. 6d. to 4s. 7d. per ton. In the rest of
the Transvaal, the saleable output increased from 74,149
tons to 79,719 tons, whilst the average pit top selling price
increased from 4s. 3d. to 4s. 5d. per ton. These figures
indicate that it is the collieries in the Coal Owners’ Asso-
ciation that are obtaining the higher price, and it remains
to be seen whether the non-associated collieries will follow
suit. Many of the latter are, however, so bound to the
South African Railways that it is doubtful whether they
will be able to take full advantage of this movement in
prices, whilst all the leading non-associated collieries have
agreed with the railways not on any account to become
members of any association. Even to-day the price of coal
in the Transvaal at 4s. lOd. per ton at the pits is absurdly
low, but the abundance of coal in the Transvaal, and the
fact that the largest buyers of coal are interested in the
collieries, tend to keep down the prices to a very low level.

Australia.

Exports from Newcastle.—The coal exported from New-
castle for the first quarter of the present year totalled
804,759 tons, an increase of 27,400 tons over the figures
for the corresponding period in 1916, which, however, was
wholly in the trade with the Commonwealth and New
Zealand ports. The quantity sent to oversea countries was
154,850 tons for the 1916 period, and 109,945 tons in the

first quarter of this year, a decrease of 44,904 tons for the
1917 period. The increase of the total value was
<£146,097, due to the increase of 3s. per ton in the selling
price, which came into operation at the beginning of the
year.

State Coal Mine. — Work at the State coal mine at
Lithgow is proceeding slowly but steadily. The shafts are
to be 275 ft. deep and 19 ft. in diameter, with a view to
striking the Lithgow general coal seam. It was found
necessary to make special arrangements for the sinking,
with a view to securing a solid foundation for the head-
gear, which is nearly completed.

New Zealand Coal Strike.—In New Zealand there is a
coal strike in progress, and there are indications that
attempts are being made to embroil the New South Wales
coal mining industry. The secretary of the Australian
Coal and Shale Employees’ Association states that if any-
one sells coal or ships coal to New Zealand, coal will be
declared black, and the mining and associated industries
will come out. The recent defeat of the Labour party at
the State elections, and the fact that the National Party
now in power have a large majority, will put the Govern-
ment in the position of being able to deal more firmly with
these vexatious labour disputes, which have done so much
to retard the progress of the coal industry in New South
Wales.

Canada.

The Nova Scotia Mining Society held its annual meeting
on April 19. This is the first meeting of the society
since the Avar, and all social functions were dispensed with.
In lieu of the annual dinner, a donation was made to the
“ Belgian Kiddies’ Fund ” now being raised by the
Canadian Mining Institute. Mr. A. J. Tonge, the general
superintendent of the Dominion Coal Company, read an
interesting paper on “ Mine Fires : Their Origin, Control,
and Extinction.”

Great activity is evident in re-opening abandoned mines
and in working coal areas so situated as to be easily acces-
sible for immediate working. High prices have interested
speculators in coal mining, but the movement is not likely
to benefit the total coal production, as the miners will be
drawn from the working forces of the large companies. A
short walk to work, and the opportunity of working in
naked-light mines is a great attraction to the old type of
miner.

Coal Production of Nova Scotia,—The coal production
of Nova Scotia is remaining stationary at the reduced
level of the past six months, and no further noticeable
decline has taken place. On the other hand, no increase
is possible. The production of the Dominion Coal Com-
pany for April was about 330,000 tons, compared with
370,000 tons in April last year. The aggregate outputs
for the first four months of the year show a decline of
210,000 tons under the production of the first four months
of 1916. A conference was called by Sir Geo.. E. Foster,
the Minister of Trade and Commerce, and Acting-Premier,
at Ottawa on April 2, to which all the operating coal com-
panies in Nova Scotia were asked to send representatives.
This action of the Government was actuated by the severe
coal shortage which affected the whole of Eastern Canada
last winter, and the fear that a similar shortage might be
repeated next winter. It appears inevitable, that this will
be actually the case, as all the factors causing the reduc-
tion in the coal supply have since become more decided.
The chief reason is the heavy enlistments among the
miners, and the next reason is the shortage of shipping
tonnage. The production of Nova Scotian collieries in
1917 will not exceed 5,750,000 tons, and it may be that the
production will not exceed 5,500,000 tons. This is some
1,750,000 to 2,000,000 tons below the. capacity of the.mines
in normal times. During the past nine months the impor-
tation of United States coal into Montreal and the neigh-
bourhood has been much hindered by railway embargoes
and the shortage of bottoms on the Great Lakes. Freights
are high, and difficult to obtain. The price, of coal in the
United States is unprecedentedly high. Bituminous coal
is quoted at 5 dols. per ton at the pit mouth, and it is
expected that the price will reach 7 dols. by autumn. The
normal price is about 1*50 dols. per ton. When to these
difficult conditions is added the almost total absence. of
importations of Nova Scotian coal, compared with ship-
ments of 2,000,000 tons in a normal season, it will be seen
that the fuel question in Montreal and the St. Lawrence
Valley is iustly causing anxiety. The best that the Nova
Scotia collieries can do this summer will be to ship
150,000 tons of coal to Montreal. Last year the shipments
were 400,000 tons only. Recruiting has. already affected
the United States coal production, and it is much to be
hoped our new Allies will learn from, the experience of
France, Britain, and Canada how suicidal to all national
endeavour and the production of munitions it is to allow
the enlistment of such specialised producers as coal miners.
Civilian opinion on this matter was contemptuously ignored
pt the beginning of the war, and the patriotism of those
who counselled caution in the enlistment of miners was
even called in question. In no part of the Empire, how-
ever, has the unrestricted enlistment. of miners gone to
neater lengths than in Nova Scotia, with results that have
been correspondingly serious and detrimental to the broad
aims of the war.

German Steel Union.—The German Steel Union has
decided to increase the selling price of semi-manufactured
steel by 50 mk. per ton for the month of July, and—in view
of the'expected rise in coal prices—by another. 10 mk. for
August and September. The price of sections is advanced
10 mk. per ton, which will also apply to all deliveries on
contracts for the present quarter that may have had to be
delayed until next quarter.

Durham Colliery Deputies and Mines Act,—A deputation
from the Durham Colliery Deputies’ Association, which
was accompanied by Mr. John Hill, Newcastle-on-Tyne,
chairman, and the Right Hon. C. W. Bowerman, M.P.,
secretarv. of the Parliamentary Committee of the trade
Union Congress, waited upon the Mining Department of
the Home Office on Thursday, with respect to alleged con-
traventions of the Mines Act of. 1908 by the working of
overtime. Mr. Walker, who received the deputation,, pro-
mised that the matters brought to the notice of the Mining
Department should have attention.

At the meeting of the Mineral Owners’ Association of
Great Britain, held at the Great Northern Hotel, London,
on June 7, it was announced that special representations
were to be made to the Government for incorporation m
the Budget with a view to the necessary expenses of employ-
ing mining engineers being allowed as a. deduction when
ascertaining the amount payable for income tax and
mineral rights duty. It was stated that the allowance is
a statutory deduction in respect of the salaries paid to
checkweighmen, and that a deduction was made for .the
expenses of management of property generally as distinct
from mines.