June 20, 1913.

THE COLLIERY GUARDIAN.

1333

Oxygen.	Nitrogen.

1	........ 17	0 ........ 83 0

2	........ 16	7 ........ 83’3

The difference between the results of Burrell and
those of Clowes and Feilmann and Eitner is perhaps
merely one of observation. The whole argument has
evidently been based only on the scantiest experimental
evidence which is totally inadequate to permit definite
conclusions to be drawn. The presence in firedamp
of any considerable amount of the higher paraffin
hydrocarbon gases—ethane, propane, butane, pentane
vapour, etc., introduces a factor which the recent Act
has not taken into account. The influence of any or
all of these gases on the inflammability of air may be
considered thus: Burgess and Wheeler (Journal Chem.
Soc., 1911, v. 99, p. 2013) give the following figures for
the lower limit of inflammability of hydrocarbon-air
mixtures :

Per cent.

M thane................. 5’6

Ethane ................. 31

Propane.................. 217

n. Butane .............. 1’65

n. Pentane.............. 1’37

i. Pentane.............. 1*32

Thus an air mixture containing 2’5 per cent, of
propane or butane or pentane (“ inflammable gas ”) is
actually inflammable, and if it contains 2’5 per cent, of
ethane alone it is near the limit. Under the circum-
stances it seems that from the legal point of view the
analytical method of Harger, involving the estimation
of total inflammable gas, may, if reliable, be useful, but
only in assisting a moral defaulter to escape the penalty
of the law by adherence to its letter. In an extreme
case an explosive atmosphere would not form sufficient
grounds for legal action. I believe, however, that
responsible managers will not be satisfied with any-
thing less than the degree of safety indicated by the
Act. The degree of safety can be ascertained from the
analytical results, calculated on the assumption that
the inflammable gas is methane, in the following way :—

Accepting Burgess and Wheeler’s figures for the
dilution limit, the limiting percentage (2’5) allowed for

2’5
inflammable gas (meaning methane) is —— = 0’45 of
5’6

the amount required for inflammability of the mixture
in the absence of the coaldust. Equal fractional parts
of the other hydrocarbon percentages are as follows :—

Ethane..... 045 x 3’1 = 1’4 percent.

Ptopane.... 045	x	2 17	=	098

n. Butane ..	0 45	x	165	=074	„

n. Pentane...	0 45	x	1 37	=	0 62	„

i. Pentane...	0 45	x	132	=	059	„

The volumes of carbon dioxide produced by the
combustion of such mixtures in a gas analysis operation
would be

2*5 volumes of methane give 2 5 x 1 = 25 volumes of C02

1 4	,,	ethane „	14 x	2 = 28		
0’98	'	,,	propane „	0 98 x	3 = 29		
0’74		n butane „	0 74 x	4=30		
0-62	,,	n. pnntane „	0’62 x	5 = 31		
0’59		i. pentane „	0 59 x	5 = 30		J,
Hence	the	amount of	carbon	dioxide produced by		

these safety-limit mixtures is rather higher when other
hydrocarbons than methane are present. Consequently
an analyst who calculates hi^ hydrocarbons as methane
from the volume of the carbon dioxide formed on
combustion of the firedamp will always be on the safe
side so far as regards actual working conditions in the
mine, and as regards the legal requirements too. If he
determines the volume of inflammable gas he may, in
the presence of other hydrocarbons than methane,
defeat the aims of the Act, but be exposed to moral
blame by permitting work to proceed in a highly
dangerous atmosphere.

Mr. Albert Parker, of the chemistry department,
Manchester University, said experiments had been
conducted recently in the chemical laboratory to deter-
mine the inflammability of methane and air containing
diminished oxygen. The experiments were made in a
glass tube, 8 centimetres in diameter and 25 centimetres
high. By means of two copper wires passing through a
rubber stopper at the top of the tube, any gaseous
mixture in the tube could be sparked at the bottom. It
had been found that methane could be exploded or
rendered inflammable in an atmosphere containing only
13’5 per cent, of oxygen and the rest nitrogen. The
particular mixture used contained 92 parts of this
abnormal air to 8 of methane. Not very many
experiments had been conducted so far, but they were
being conducted and it was hoped he would be able to
furnish further results within a short time. But this
particular result showed that methane could be exploded
with air containing less than 17 per cent, of oxygen. In
the particular experiment referred to, the flame travelled
right through the centre of the tube to the top and down
the outside at a rate of about 100 centimetres a second.

Mr. W. Hutchinson Murray, H.M. inspector of
mines (Liverpool), said that what really concerned the

practical mining man was the composition and the
behaviour of the firedamp actually met with in the mine.
In his paper, Dr. Harger called attention to the varying
composition of firedamps, and it was, of course, a matter
of common experience with many of them that firedamps
appeared to vary in their characteristics in different
seams. In one seam they found firedamp with a strong
characteristic smell, and in another, with little or no
smell. Some firedamps were described as being quick in
the lamp and others comparatively slow. At the outset
of his paper, Dr. Harger found fault with the present
method of testing the ability of firemen to recognise
firedamp caps by the use of town gas, on the ground
that the composition of the town gas varied so much.
Was Dr. Harger quite consistent in that? Did he not
immediately devote the greater part of his paper to
showing that firedamps varied greatly in composition
also? On his own showing, it would be no better to use
an artificially-prepared methane. The suggestion made
by Mr. Williams, of storing up firedamp from a blower
in South Wales appeared to be a practical one, but even
then it did not seem quite a desirable thing to test
firemen in, say Lancashire, with a gas from a South
Wales field. After all, the use of town gas did not
appear to him to be so undesirable, especially as the
conduct of the examinations was in the hands of
eminently practical colliery managers.

But the most interesting part of Dr. Harger’s paper
was the part in which he dealt with the composition
of firedamp. He asserted that “ the pure methane
assumption was entirely fallacious.” But while they
must admit that small quantities of the heavier hydro-
carbons were occasionally found, they were, he thought,
in such small quantities as to be negligible from a
practical point of view. He was, of course, speaking
of the gases as actually found existing in mines, and
not those drawn off from coal in a laboratory. In 1875,
Thomas made analyses of many samples of almost pure
firedamp taken from the coal face, and from blowers in
South Wales collieries. In only one of those cases was
any other inflammable gas than pure methane found,
and that was only 0’9 per cent, ethane in a sample
containing about 90 per cent, methane. In 1910
Dr. Gray read a valuable paper on firedamp before the
Mining Institute of Scotland, and put it on record
that “ the firedamp present in the air in coalmines
seemed to consist entirely of CH4 in all the cases
examined.” Dr. Gray analysed 72 samples. In the
recently published “ Third Report of the Explosions
Committee ” the results of ten analyses of different
samples of almost pure firedamp, collected, it may be
assumed, from all over the country, were given. The
largest amount of hydrocarbons other than CH4 was
1’8 per cent., and in only three out of the ten was
inflammable gas other than methane found. The well
known blower of gas from the Ravine seam at Garswood
Hall Colliery was known to contain 2’8 per cent, of
ethane out of 85 per cent, of inflammable gas. Those,
as far as he was aware, represented the principal
results of analyses of firedamps actually got in coal-
mines, and none of them showed sufficient of the
higher hydrocarbons to affect the result of a sample
containing, say, 2^ per cent, of gas, within the limits of
experimental error. It occurred to him that none of
those samples were taken from old goaf, and Dr. Harger
made a special point of that. Through the courtesy of
some of the managers of the collieries in Lancashire he
was able to collect a few samples of fairly pure firedamp
from old goafs. One sample taken from the old goaf of the
Cannel coal or Wigan Four-feet seam, at a place showing
a high temperature, gave 73 1 per cent, of inflammable
gas. Hydrogen was tested for and found to be absent,
and the inflammable gas was CH4 only. Another
sample, taken from the old goaf of the King coal, gave
29 6 per cent, inflammable gas; a third from the Wigan
Nine-feet seam gave 24 6 per cent, inflammable gas, and a
fourth taken direct from the coal face in the Ravenhead
main delf gave 89 per cent, firedamp. In every case
hydrogen was absent, and the gas consisted of CH4
only. Those analyses were made by Dr. Murray, of the
Wolverhampton Technical School, and were carefully
watched for indications of the higher hydrocarbons. So
far, then, the presence of higher hydrocarbons appeared
to be negligible for practical purposes until they came to
Dr. Harger’s figures. Those figures, given in Table III.
of the paper, were worth studying. They were the results
of analyses of firedamp from a mine, the name or situa-
tion of which was not given. On looking at the rates
between contraction and carbon dioxide formed, and
assuming that the inflammable gas other than CH4 was
ethane (which was the most probable of the higher
hydrocarbons), it would appear that sample 15 showed
the presence of a firedamp containing 17J per cent,
ethane, sample 16 a firedamp contain’ng 26 per cent,
ethane, and sample 18 a firedamp containing 12 per cent.

ethane. Sample 12 was even more remarkable, as it
showed the presence of hydrogen, and if there was no
counterbalancing ethane, the hydrogen must compose at
least 19 per cent, of the inflammable gas. Quantities of
ethane or hydrogen such as those have never before been
found in gases in a coalmine by any other observer, and he
would point out that Dr. Harger based his assertion
that they were present on those figures, which appeared
o be the analyses of air containing anything from 0 08
per cent, to 0’38 per cent, of firedamp, and that, moreover,
the question of the presence of ethane at all, would seem
to depend on the accuracy of the second decimal place.
They were asked to accept the fact that in “ the same
mine on different days and in different places ” the
composition of the inflammable gas varied from pure
methane to a mixture of 74 per cent, methane and 26 per
cent, ethane or to a mixture of 19 per cent, hydrogen
and 81 per cent, methane. Had more particulars of how
those samples were taken been given, or had they been
taken in the vicinity of a gob fire, one might understand
them, but in the circumstances, they could not be taken
as truly representing “ firedamp in coalmines.” Dr.
Harger used one other argument in support of his
contention. He gave the result of analyses extracted
from Barnsley coal under vacuum and after heating.
But that did not prove anything regarding the compos-
ition of the gases in the mine. It rather proved that
coal retained those higher hydrocarbons more tenaciously
than it did methane, as had been already pointed out by
Thomas, Bedson and others.

Mr. Geo. B. Harrison, H.M. inspector of mines
(Manchester), said that practically the same ideas as
those just expressed by Mr. Murray occurred to his
mind when Dr. Harger was reading his paper, and when
Dr. Harger so severely criticised the method of testing
the capabilities of firemen. Dr. Harger, while com-
menting on the differences in the qualities of town gas,
went on to show that there were very marked differences
in mine gases. It occurred to him that it was of little
use testing a man with pit gas if it varied so much, and
that the true test was to be found in the man’s manner
of handling the lamp, and finding a cap of gas if any
was there. It must not be forgotten that the exami-
nations were by practical men, men of experience.

Colliery Cables.

In the course of a short discussion on Mr. Anderson’s
paper on “ Colliery Cables,” Mr. Harrison emphasised
the vital importance of seeing that the earthing
arrangements were good, so that in the event of a
breakdown there was no danger of workmen being
killed or injured.

Before separating, the President reminded the
meet ng of the forthcoming visit of the Institution of
Mining Engineers to Manchester in September next,
and asked the members of the Manchester institution
to do their part in making the visit a success.

SOUTH STAFFORDSHIRE AND WARWICKSHIRE
INSTITU E OF M NING ENGINEERS.

A meeting of this institute was held at the Council
House. Walsall, on Monday, June 16, the President
(Dr. J. Cadman) in the chair.

The minutes of the last meeting were read and
confirmed.

The President proposed a vote of congratulation to
Sir Francis W. T. Brain on his receiving the honour of
knighthood, and mentioned that he had been a member
of this institute for 17 years.—The vote was seconded
by Mr. Alexander Smith, and heartily accorded by
the members.

A vote of thanks to the Property Committee of the
Walsall Town Council for the use of the room at the
Council House was proposed by the President,
s?conded by Mr. G. N. Cockin, and carried unanimously.

The scrutineers and auditors for the coming year
were appointed as follows:—As scrutineers, Messrs. J.
Hughes and F. G. Meachem ; as auditors, Messrs. T. J.
Davies and W. H. Whitehouse.

The President then called upon Prof. S. M. Dixon
to read his paper, which was illustrated with lantern
slides.

Reinforced Concrete in Mines.

The author commenced by disclaiming any ability as
a mere civil engineer, but professed to stand in the
position of a special pleader for a more extended use of
reinforced concrete in mining work.

Four totally different classes of structural work, he
said, have to be carried out by mining engineers:
Surface works, shafts, permanent roads, and temporary
roads.

1. Surface Works of all Kinds.—These works, as far
as being engineering structures, are of exactly a similar
kind to those carried out by engineers in charge of any
kind of building work, except perhaps that in some
cases they are more liable to the effects of settlement.
It is now admitted that reinforced concrete will always