1274

December 18,1914

THE COLLIERY GUARDIA^ T

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bring all the States. , under one agreement, but the .
operators had not conceded the point. While by far
the larger part of the output of the United States of
America, probably oVer three-quarters, was produced
under industrial union agreement, there were some dis-
tricts that were not, such as the Connellsville. coke
district in Pennsylvania, the larger part of West
Virginia, including the New River and Pocahontas
smokeless coals, part of Eastern ~	""

nessee, all of Alabama districts,
Colorado and New Mexico.

Messrs. H. H. Stoek and S.
Illinois, U.S.A.) wrote that Mr.
mining practice and conditions
purpose admirably, but a few of his statements referred
to local rather than to general practice. With regard to
the closing of the mines regularly about April 1 every
two years, it must be remembered that Illinois coal was
not particularly adapted to storage, and, as a conse-
quence, in the spring and summer months, when the
market was dull, the production was materially
decreased. Furthermore, the mines were not always
closed during this period, although this was frequently
the case. With reference to the quantity of coal shot
off the solid, it might be of interest to note that 49 per
cent, of the entire coal production of the State was
undercut by machines. The machine mined coal
steadily increased in quantity, whilst the amount of
so-called “ hand mined ” coal remained constant. This
meant, of course, that in practically all new mines coal
cutting machines were being installed. The present
annual output of machine mined coal was over
30,000,000 tons. It was regrettable that “ permissible ”
explosives were not being introduced as rapidly as Mr.
Dean’s statement seemed to indicate. The use of such
explosives was confined almost wholly to a county in
which only 7 per cent, of the output of the State was
produced, this county accounting for 99’5 per cent, of
the quantity used in Illinois. . The objection of the
operators to the use of permissible explosives was based-
on the fact that, under the methods of blasting in
force, from 5 to 10 per cent, more coal .under	in. in

size was produced by their employment; also to the
fact that controversies in regard to the mining wage
rates had usually resulted from their introduction.
While it was true that the attempts at extraction of
pillars in Illinois were lamentably unsuccessful, it
should be remembered that the small percentage of
pillar coal thus recovered was due to the adoption of
improper dimensions of room and pillars, a considera-
tion which rendered a “ squeeze ” inevitable when
pillar drawing was attempted. Unsuccessful attempts
at extraction were often made. The amount of coal
left in the ground was probably nearer 40 than 50 per
cent.; but, even after an examination of 150 mines by
the engineers of the Illinois Co-operative Investigation,
it was difficult to determine any definite figure. With
respect to haulage equipment, the coal was transported
from the far end “ partings ” by mules in 168 shipping
mines, by cable in 13, and by electric or gasoline loco-
motives in 185 mines. The electric locomotives in use
in several mines were of the third rail type. Electric
gathering locomotives were used in comparatively few
mines for secondary haulage, but these locomotives
were employed in the more recently opened mines, and
only a few in the old collieries. Only one mine had
come under the writers’ observation in which the use
of gathering locomotives had been discontinued and a
return made to gathering with mules. It would have
been impossible to maintain rectilinear entries at this
mine, except at a prohibitive expense, on account of
the numerous rolls in the roof and floor, a circumstance
which demanded a great amount of drifting in hard
rock for the maintenance of straight entries. The
added cost in haulage, a small fraction of lc. per ton,
was offset many times in the lessened cost in entry
driving. The average capacity of the pit cars (or tubs)
was two tons or less. In many mines the capacity of
the pit cars was from 1 to 1| tons. Shafts sunk during
the last few years were lined with concrete or brick, or
with timber covered with cement. While a few
operators were fearful of the use of carbide for acetylene
gas illumination, the acetylene gas lamp was general in
Illinois mines.

Hydraulic Stowing.

Mr. B. C. Gullachsen’s paper on “ Hydraulic
Stowing in the Gold Mines of the Witwatersrand ” was
further discussed.

Mr. Geo. S. Rice (United States Bureau of Mines)'
said dry stowing and caving had largely replaced square
set timbering methods in the United States, and, while
the various caving and sub-slicing methods were hard
to improve upon in working many kinds of ore bodies,
particularly those in the Lake Superior iron ore district,
there was, undoubtedly, an extensive field open for
hydraulic stowing in some of the deep metal mines. It
was somewhat surprising that hydraulic stowing had
not been used except for a few restricted applications.
It was all the more surprising, considering the extensive
employment of the system in the anthracite district of
Pennsylvania. The employment of hydraulic filling in
the anthracite mines of Pennsylvania had continued to
expand to the present time, and, judged simply as a
filling system, the writer’s personal observation led him
to think that its use was as far advanced in that district
as in the Silesian coalfield, but, for first or advance:
mining, its application had only recently been started in
the former place. One of the greatest obstacles in ’
retarding the introduction? = of hydraulic stowing 'had

to permit of that additional cost being incurred. The
problem of supporting the surface was, however, a very .
serious one in some localities, as the region was densely .
populated, and, in consequence, there was much litiga-
tion and trouble, particularly in the city of Scranton.
Mining was continuing under the city at a present rate,
of 6,000,000 tons per annum. Under such conditions
there had necessarily been serious subsidences from
time to time, and many buildings had been wrecked,
although, fortunately, accompanied so far with
practically no loss of life. No broad comprehensive
plan had yet been agreed upon. Most mining engineers
who had investigated the situation—including the writer
and other engineers of the Bureau—believed that in
hydraulic filling lay the only solution.

were the ease, his exposed wire should assume.;a.higher
temperature in the. presence of firedamp than in its
absence, unless there was combustion going on in the
air immediately in contact with its heated surface. Mr.
Ldon had found that the indications of his instrument
varied in consequence of changes in the conductivity of
the, exposed wires,, due to heating and cooling, as well
as changes in the strength of the accumulator.

Messrs, H, H. Clark and G. A. Burrell (United
States Bureau of Mines, Pittsburg) wrote that Mr.
Ralph’s device, was of the greatest interest to the staff
of the Bureau. It would appear desirable that the
actual tests made by Mr. Ralph should be reported in
detail, in order to demonstrate the sensitiveness of his
instrument, and in support of his statement that there	_____________________________

would be little or no permanent change in its resistance.
If that wdre the case, then frequent re-calibrations
against known methane-air mixtures would not have to
be made, and one of the chief difficulties in the way of
utilising the properties of platinum wires when heated
in the presence of methane would be overcome. The
change bf electrical resistance of platinum per degree
Cent, change in temperature was about 0-3 per cent.
The means suggested for observing that change of
resistance, while excellent in theory, could, in the
circumstances, hardly be expected to be very sensitive.
It would be surprising, therefore, if small amounts of
gas (say, less than 1| per cent.)'could raise the tempera-
ture of the platinum Sufficiently to give trustworthy
indications, especially1 when one took into consideration
the variable conditions of supply of heat to and loss of
heat from the . active wire, , such as change in battery
voltage, changes .in air temperature, and draughts of air
—-all of which, migfit well be” encountered in practice.
The bureau had encountered' 'sdm'e of these difficulties
in working on a somewhat, similat-^device. Mr. Ralph’s
excellent method of measuring thfe resistance of the wire
was noted. By that scheme he apparently increased
the. sensitiveness of, tfi^ apparatus over what it would be
if only the deflection of the galvanometer pointer were
measured. For that and other improvements over
preceding device#,' MrRalph deserved much praise,
as well as for his persistence in the study of a problem
of so much importance to mining men.

Illinois Coal Mining.

Mr. 'Samuel Dean’s paper, “Notes on Coal Mining
in the State of Illinois, United States of America,’’ was
further discussed. , , ,

Mr. Geo. S. Rice (United States Bureau of Mines,
Pittsburgh wrote that, from the European point of view,
judging from the many enquiries made by visitors, the
most striking feature in mining in the United States—
to which Illinois was no exception—was that only one
coal seam was worked in a locality, excepting in the
case of the anthracite district and a few smaller
localities. Mr. Dean’s statement that there were six
seams of coal in Illinois merely meant that, in some
locality or district there, one or other of the six were
being worked. The chief reason why not more than
Ohe seam was worked in any one locality was that the
margin of profit was so small that it paid only to work
the thickest or best seam. As Mr. Dean had stated,
the general method of working was by room and pillar.
The only longwall working of any importance was that
of Northern Illinois in connection with the mining of
the No. 2 seam, which was the second seam from the
bottom of the coal basin. That was the only extensive
longwall district in the United States, and had an
output of 5,000,000 tons per annum. The great loss
of coal in the room and pillar mines in the central and
southern parts of the State was due to three factors :—
(1) The purchase price (rent) of the coal was so low,
generally less .than lc. per ton, that there was
no incentive to good mining; (2) the difficulties of
extracting the pillars, unless the system of retreating
from the boundaries was employed, which would mean
a larger investment than the operators were willing to
consider; and (3) which had an influence on the second
proposition, as the value of the surface for agricultural
purposes was generally greater than that of the coal in
the ground, any subsidence of the surface, which was
quite flat,.disturbed its drainage, particularly as most
of the ground was tilled. The surface was worth from
£22 10s. to <£56 5s. per acre, whereas the coal could be
purchased at from £3 2s. to £22 10s. per acre. The
large loss of 50 per cent, of the coal which occurred in
mining the No. 6 seam in the Central district, a per-
centage which was very high even for room and pillar
workings, was due to the necessity of leaving large
pillars and their non-recovery. When the pillars were
made smaller, the strong roof over the middle and
southern part of the field, which contained a heavy
limestone 5 or 6 ft. above the coal, did not break, but
pushed the. coal down into the clay underlying the No. 6
seam. That clay was comparatively soft and 6 or 7 ft.
in thickness-, and the depth of the coal below the
surface was from 400 ft. to 600 ft. With regard
to head frames, Mr. Rice said he had never
observed any mines in which there was not at least one
man at the pithead to see whether the pit car on the
self-dumping cage was dumping properly and to “ bell ’’
away the cage. It was not usual to weigh the pit cars
underground,.the more general practice being to dump
the.cQal, by means of the self-dumping .cages, into weigh
hoppers, which discharged on to the shaking screens.
The aggregate advances in the rates ranged from 25 to
50 per cent; since the collective system of bargaining was
begun about 1897. Similar trade agreements were in
effect in the competitive States of Pennsylvania, Ohio,	____________ ___ _______ ______

and Indiana, being sometimes entered into at joint been-lack of suitable ffilling material: many of the old .:
meetings,'and \atjpther times by separate States. Otherrefuse jumps had . already, disappeared,. and ,thq^
groups, of States/had similar jointagreemehts?.witji the - ; remaining dumps were fast being hydrauljcked into. ,	______:__ _______........	. ... .	- ... ..

miners, .through their, great ind.ustriaV,union, the United . the■■ ‘mines/ Mind Operators’claimed that at present the * See Colliery Guardia#! October*’16, p. 833; Trans.; In$t. -
Mind Workers of America, •< That;union ]had;-tried, .to omarket price for the coal was too close to the mine cost :“Min.'Efigin-; vol. 48, I, p. 79.	-

Kentucky and Ten-
and some districts in

0. Andros (Urbana,
Dean’s description of
in Illinois served its

FIREDAMP DETECTORS.

At a meeting of the Manchester Geological and Mining
Society on Tuesday, December 8, Mr. George Ralph
gave a demonstration of a firedamp meter, and also
addressed the members at some length on firedamp
detectors generally. The electrical method of detecting
gases, he said, had been a favourite one with many
people for years past. The late Sir Joseph Wilson
Swan, the inventor of the incandescent lamp, devised
an electric gas detector, for which he obtained a patent
in 1887, but prior to that Dr. Liveing had invented an
electric firedamp detector which, so far as he knew, was
the only one which had been used in mines at all. The
Liveing detector certainly worked, but it had grave
defects. One was that for the platinum wires to give
any light at all it had to be run at a very high tempera-
ture, and if the operator happened to turn the handle of
his magneto machine a little too fast he burnt out his
wire. Another point was that although platinum was a
very permanent substance, owing to the high tempera-
. ture the wire was worked at, it soon oxidised and burnt
away, with the result that the zero of the instrument
did not’ remain constant. Mr. Ralph then described his
original device and the instrument more recently devised
by him.* Specimens of this he submitted for their
inspection. At the present moment, he said, a sample
was undergoing official trials at the Eskmeals testing
station. He believed that so far they had been very
satisfactory. Mr. Ralph said the weight of the apparatus
was about 2| lb. Having been originally designed for
attachment to a miner’s lamp, it had taken a shape
which was not convenient for the pocket, but he proposed
to modify the design so that it would go readily into the
pocket. It had also occurred to him that the apparatus
could be «used over the head by putting a reflector above
the pointer so that the deflection of the needle could be
observed.

The question had been raised by the Home Office
officials as to whether its use would be a contravention
of the Mines Act, because there was a clause in the
Regulations (No. 35, he thought) that no means of
making a spark or creating a light, other than a locked
safety lamp, must be used in a mine. However, he was
led to believe that if the instrument was shown to do
what he hoped, that Regulation would be so modified as
to permit its use. Of course, the question of safety
came in. There was a hot wire exposed to the atmo-
sphere, but it was protected by gauze in the same way
as the flame of the safety lamp. Whether the apparatus
met a want remained to be seen. At all events, it was
a great personal satisfaction to achieve the object he set
out to attain.

The Chairman (Mr. Leonard R. Fletcher), in moving
a vote of thanks to Mr. Ralph for his demonstration and
paper, said, in his opinion, the instrument seemed likely
to prove a most useful one.

Mr. J. Gerrard (late H.M.I.M.) said he had great
pleasure in seconding the vote of thanks. Personally,
he was not prepared to say that Mr. Ralph had fully
accomplished what he set out to attain, but he was
quite sure he had opened the way for further improve-
ment. There could not be two opinions as to the desir-
ability of having some device for detecting the presence
of firedamp which could be used along with the electric
lamps by miners when engaged in their working places.
Electric lamps were now being largely introduced into
mines, and in the Manchester district there were several
collieries where they were used, in varying numbers,
from 100 to 200, and those who were anxious for the
safety of the men felt some diffidence as to the detection
of gas; they were by no means satisfied that the miner
should be permitted to work continuously under condi-
tions which exposed them to the danger of a sudden out-
burst of firedamp unless all possible precautions were
taken. He thought he had gathered the principle upon
which Mr. Ralph proceeded, but he would like to hear ,
an explanation of how he got the magnification showing
the percentage.

The vote of thanks was carried.

' Prof. H. B. Dixon (Manchester) said he' had hot'
: heard the whole of the explanation given by Mr. Ralph,
“nor had he had a chance of looking at the details of his