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38 THE COAL TRADE BULLETIN.
The equipment purchased for the Rend mines
has balancing coils designed to carry continuously
loads unbalanced to the extent of 50 per cent., or
even higher proportions temporarily. It is expected
to keep the unbalancing much below this
figure, probably within 25 per cent. Two wires
will be carried into the mine, while the third wire
or neutral will be grounded to the track rail. The
potential between either wire and the ground will
therefore not exceed 275 volts, and locomotives.
machines, etc.. will be operated between either
wire and the rail. The two wires, between which
the potential is 550, will be carried at opposite
sides of the entry, so it will be difficult or impossible
for miners to make contact across these
wires.
With such a double circuit in each of the four
mines, the total load will be carried by eight approximately
equal feeder circuits. The feeder
switches will be double throw, so connected that
any feeder may be transferred from one side of
neutral to the other, should this be found necessary
at any time to aid in balancing the circuits.
Three-wire generators, of the type described,
are in operation in a number of lighting plants,
with incidental power circuits. The Oliver power
plant, in Sixth avenue. Pittsburgh, is a notable
example. The application of this system to mining
work is, however, a new departure, but it is
believed that it is destined to become a very valuable
feature in the development of mining properties
of large acreage, with correspondingly long
power transmission lines under ground.
GOOD RESULTS FROM MINES
WORKED BY CONVICT LABOR.
Chief Mine Inspector J. M. Grav, of Alabama.
has prepared a report on a personal examination
of the convict mines at Flat Top. Among other
things the report says:
"The company broke all previous records last
month on coal production. I was very proud to
hear this, owing to the fact that tne system of
shooting had been changed two or three months
ago and it has not only increased the production
per man, but has made the condition of the mine
better. I believe it will reduce the number of
accidents from falling rock and coal, and beyond
the question of a doubt it has removed the liability
of a magazine explosion. The bottom entries are
being driven narrow and eye holes four feet by
ten feet by twenty feet cut in the pillars to store
the rock. This makes the entries look very clean
and neat. It also lessens the labor of the convicts
as they only have to build a wall four feet
high whereas by the old system they had to pile
it up six to eight feet high and it was very hard
work to lift or pitch a heavy piece of rock so high.
The mine at present is damp and there is no dust
in it to amount to anything, and there is but little
inflammable gas being given off. At the mine they
have a very strict and exacting discipline among
the men concerning shooting and handling of the
powder and dynamite. The managers in and at
the mines as well as the higher officials of the
state and company, are very prompt in carrying
out orders from this department and justly deserve
credit due them for the excellent condition of the
mine."
The Sloss-Sheffield Sleel & Iron Co. operates the
mines.
EFFECTS OF MINE STRIKES ABROAD.
The recent strike of miners in Belgium and
Germany has materially increased the British coal
exports, but the British exports to Belgium increased
only 24,000 tons, which is accounted for
by the large supply of coal on hand in Belgium at
the commencement of the trouble. Over 100,000
miners were on strike in this country for a considerable
time, and those in the Charleroi and
Borinage districts were idle much longer. It is
estimated that the coal supply in Belgium was at
least 1,000,000 tons when the strike was ordered.
A coal famine might have been feared h?d not
some 60,000 miners remained at work. The
French coal dealers profited considerably by the
strike, and had their supply not been already reduced
by shipments to Germany their export
would have been larger to the Belgian market.
England found her most lucrative field in the
Netherlands. In the first quarter in 1904 England
shipped to that country 193.459 tons of coal,
and in the first quarter of 1905, 843,346 tons. Feb
ruary registered the greatest increase, the total
shipments in February, 1904, being 68,906 tons,
against 483,745 tons in the corresponding month
of 1905. The Westphalian mine owners have
lately entered the field against the British dealers
and have cut into their trade materially, having
secured the contract for The Hague gas works and
two-thirds of that for the work at Rotterdam.
The British estimate of their coal exports to Belgium,
Germany and the Netherlands for the first
quarter of 1905 is 1,500,000 tons in excess of that
for the first quarter of 1904. The export, however,
to all countries shows an increase of only
500.000 tons, demonstrating that while the British
dealers are improving their trade in the countries
named there are decreased sales elsewhere.
Excursions to Colorado For Eagles Grand Aerie
August 11th and 12th.
via Pennsylvania Lines. Special low fares to
Denver, Colorado Springs or Pueblo. For information
about stop-overs, routes, etc., apply to J. K.
Dillon, District Passenger Agent, 515 Park Building,
Pittsburgh, Pa.