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50 THE COAL TRADE BULLETIN.
Ordinarily in Illinois a machine will cut from 60
to 120 tons a day. depending on the thickness
(running from 5 to 10 feet I and the character of
the coal.
As to cost, the estimates given herewith are
close enough to give an idea as to what an in­
stallation will amount to:
A 3-machine plant will cost $3,500
A 6-machine plant will cost 5,500
A 10-machine plant will cost 8,000
A 15-machine plant will cost 12.000
A 20-machine plant will cost 14,000
The prices include a horizontal return tubular
boiler for the small plants, or a battery of two
boilers with the large, a straight-line air com­
pressor (capable of running the given number of
machines), two air receivers (one large for stor­
age, and one small to trap the moisture from the
air in the mine), the required number of mining
machines, pump for water-jacket circulation, and
a complete pipe system, including main, branch
and room pipe with all fittings. All freight, labor
and foundation material are likewise included.
ELECTRIC LIGHTS AND COAL DUST.
At a recent meeting of the Manchester I England )
geological and mining society, H. M. inspector
of mines Hall called attention to Mr. Holliday's
paper read before the North of England Institute
of Mining and Mechanical Engineers, with reference
to the ignition of coal dust by electric lamps.
Mr. Holliday had had a fire in his colliery, with
which he suspected the electric lights had some
connection. This led him to make experiments
which confirmed his suspicions. Mr. hall said:
It has usually been held that electric lamps give
off very little heat, and that they may be placed
almost anywhere with safety. This impression
Mr. Holliday declares, he has proved to be quite
erroneous. He shows there is considerable danger
from fire, and also from the exposure for an
instant of an open light when the lamp bursts. I
have repeated Mr. Holliday's experiments, and
the results bear out entirely what he has stated.
I found that when a 16-candle lamp rested on coal
dust, either uncovered or partially covered, heat
was generated very rapidly. In one case, with a
slight covering of dust, the temperature rose in
ten minutes to 370° F., and in 4 minutes the
lamp exploded at a temperature of 450°. The
highest temperature registered was 650°. In two
out of three experiments, the coal dust was found
to be red hot on poking into the dust, although
the lamp (the apparent source of heat) had been
removed some time. The interesting part of these
experiments seems to be that when the heat has
been raised to a certain temperature, spontaneous
combustion begins to operate, and the temperature
goes on increasing till fire is reached (although
the lamp has been removed). These phenomena
show that unless care is used in the placing of
electric lights underground there will be danger
of underground fires, and some danger of fire­
damp being ignited by the explosion of a lamp.
The experiments will be carried further, with the
view of finding what is the temperature at which
coal dust will begin to develop spontaneous com­
bustion.
Man Put His Foot In It 10,000 Years Ago.
The first human imprint ever found in anthra­
cite eoal was discovered by Michael Sincavage, a
miner at the Eagle Hill colliery recently, the
print being that of a man's foot. Fossils of
snakes, ferns, etc., have been plentiful, but this
is the first evidence that prehistoric man was in
existence in this country during the formation of
the coal beds. The imprint, it is estimated, must
have been made 10,000 years ago. Sincavage, not
appreciating the value of his find, dumped it in an
ordinary coal wagon after he had shown it to
fellow-miners.
RECENT COAL TRADE PATENTS.
The following recently granted patents of in­
terest to the coal trade, are reported expressly for
THE COAL TRADE BULLETIN, by J. M. Nesbit, patent
attorney, Park building, Pittsburgh, Pa., from
whom printed copies may be procured for 15
cents each:
382.
Mining car, R. R. Hopkins, Oskaloosa, la.; 799,-
Hydrodynamic pump for bore holes and the like.
Waclaw Wolski, Lemberg, Austria-Hungary; 799,-
428.
Process of mining sulphur, also apparatus for
mining sulphur (2). Herman Frasch, New York;
799,642 and 800,127.
Drill for mining purposes, James Tonge, Jr.,
' Vesthoughton, near Bolton, England; 799,880.
Wick for miner's lamp, W. A. Wilson, Murphys­
boro. 111.; 800,041.
At Baltimore recently the Middlecreek, Shamrock
and South Side Coal companies were absorbed
by the Southern Coal Co.. all of Somerset county.
Pa. The Southern Coal Co. is now capitalized at
$300,000. The officers of the company are Frank
Ehlen, president; Benjamin H. Read, treasurer,
and Harvey M. Berkley, secretary. A mortgage to
protect a bond issue of $200,000 has been recorded.