1186	THE COLLIERY GUARDIAN.

May 29, 1914.

burning gas being invisible until the flame is lowered. But
a decided elongation is discernible with 2 per cent. As
the proportion of gas increases, there will be a greater
disturbance of the flame. Having detected the presence
of at least 2 per cent., there is really no object in
pursuing the investigation further. There is no reason
why the fireman should spend further time amusing
himself in ascertaining the exact percentage present in
various parts of the cavity, because his' duty is clearly
defined when he has satisfied himself as to the presence
of gas. If this indication is observed at some distance
from the roof, he can safely assume that the percentage
near the roof is higher. For practical purposes, this
method is quite satisfactory, and if no gas is indicated in
this test, the fireman is justified in not reporting gas in
that cavity. If, however, the top of the cavity cannot
be reached with, a stick, some means must be provided
to enable the officials to examine near the roof. Ladders
are usually provided for this purpose. The examiner
steps on the ladder, and, with the lamp in his hand, or
on the end of the rod, makes the examination in the
usual way.

It is possible, however, for a layer of gas to remain
undetected unless provision is made for the air that
feeds the flame to be drawn in from the top of the lamp.
Lamps of the Gray type are fitted so that the air may be
tested to within an inch or two of the roof.

The writers are convinced that this method is highly
satisfactory, and that a fireman who carries out his
examination on those lines is not neglecting his duty,
either to his employers or to the men for whose safety
he is responsible. Attention should also be directed to
the danger arising from an ascent into a cavity, without
first of all having some knowledge of the state of the
air in such a place.

The reliability of this method, however, having been
called in question, the writers have recently further
supplemented their experience by carrying out a number
of tests as to its efficiency. The experiments were
made in the laboratory of the Wigan Mining College,
using the following lamps in the Oldham gas-testing
chamber :—Bonneted Clanny,burning colzaline; deflector
(Marsaut), burning colzaline; deflector (Marsaut), burn-
ing a mixture of two of colza to one of paraffin; Marsaut
with Naylor Bifold burner, using paraffin; Davy, burning
colzaline; Davy, burning a mixture of two of colza to
one of paraffin.

With a 5 per cent, mixture the usual cap was obtained
when the flame was about in. high. Without remov-
ing the lamp from the chamber, the flame was raised to
about | in., with the result that all indications of gas
apparently disappeared. The conclusion that might
readily be drawn from such a test is, that “ a normal
flame gives no indication of gas, even when 5 per cent, is
present.” This phenomenon has been demonstrated

Fig. 1.—View of Lamp showing
Line of Sight.

over and over again to hundreds of students within the
last four years. When such a test is made before an
experienced fireman, the obvious result is to upset his
mental balance, because he has always had the impres-
sion that he could detect smaller" percentages by means
of the normal flame.

That such a conclusion is entirely misleading was
proved by the following experiment :—The lamp was
withdrawn from the mixture and swung about in fresh
air for a minute or two. With the normal flame it was
again inserted into the chamber, which still contained
5 per cent, of gas. It was at once noticed that an elon-
gation of more than | in. took place, and the flame was
observed to flicker. The experiment was then repeated
with the following mixtures : 4 per cent.; 3| per cent.;
3 per cent.; 2J per cent.; and 2 per cent.; and even with
the latter percentage, using a flame in. high, an elon-
gation of about was easily observed. Immediately
after each experiment, the percentages were confirmed
by using the standard reduced flame.

A second series of experiments was then proceeded with,
with the object of more nearly imitating the conditions
when testing in cavities. For this purpose gas was
allowed to issue from a pipe near the roof of the
laboratory, which is 13 ft. above the floor and 10 ft. above
the working bench. The gas pipe was so arranged that
different percentages could be obtained at different parts
of the room, and, at a height of 10J ft., from 2 to 3 per
cent, could be got by moving the lamp laterally. It was
found that these percentages were practically constant
for over an hour. Steps above the bench afforded easy
access to the roof, so that the proportions of gas could
be estimated with the .reduced flame by observing the
cap. Tests were now made in mixtures showing 3 per-
cent. and under. A 4 in. cap was obtained with the
standard flame several times, indicating 3 per cent., and
on every occasion the normal flame test quickly followed
the other, with striking results. Where the cap showed
2| per cent., the presence "of gas was also invariably
detected with certainty; the elongation observed in this
mixture being about | in. Then followed tests in 2 per
cent, of gas, and on every occasion the writers could not
fail to see that an elongation of about -'q in. took place.
The spiring of the flame takes place quicker in the higher
percentages, but the operator always has time to adjust

his eye at the proper angle before it occurs. The time
taken to carry out a test with proper care is about
20 secs., that is, placing the lamp on the rod, raising it
slowly, detecting the gas, and bringing down the lamp.
Whereas, to test with the lowered flame takes about
15 secs., apart from the time taken to reach the top of
the cavity.

The assertion that an elongation of yV in. can be
observed at a distance of 6 ft. from the lamp may be
regarded with suspicion by some mining men, but a
moment’s consideration will clearly show that there
should be no difficulty at all, and that the method is
thoroughly scientific. It has long been known that the
essential features of a lamp for gas-testing are great heat
and little light. This principle was embodied in Dr.
Clowes’ hydrogen lamp many years ago. The sensitive-
ness of the hydrogen flame as an indicator is due to its
high temperature and non-luminosity. It is also well
known that a safety lamp gives better results when hot
than when comparatively cold. Greater heat is, of
course, obtained with the larger flame than with the
smaller one, but the fireman is still faced with the
difficulty of increased luminosity. He overcomes this
difficulty in a perfectly simple but very effective manner.
He manipulates his lamp in such a way that the flame
itself is shielded from view; the line of sight just cutting
the top of the flame.

Deference to fig. 1 will make this point clear. It will
be seen that the line of sight from the observer’s eye
cuts the lamp frame near the bottom of the glass at a,
the flame at b, and the upper edge of the glass at c.
Usually, the asbestos ring above the glass serves as a
very good guide for the eye. But the angle that the line
of sight makes with the vertical will depend upon the
design of the lamp. The slightest elongation of the
flame brings it above the line of sight, and it is thus
immediately observed.

Fig. 2.—Diagram illustrating Laboratory
Tests.





•vs''

a
s

&
&
o
g
s

o /•£•	20	2$-	3 0	3-S	4-0	So

Percentage of gas.

Fig. 3.—Curve showing Elongations of
Normal Flame.

Four possible positions of the eye are shown in fig. 2,
which illustrates the manner in which the laboratory
experiments were carried out. Holding the lamp in the
hand and against the roof, the eye would be about 2 ft.
from the lamp, as at a; with the lamp on a 4 ft. rod,
the eye would, be about 4 ft. from the lamp, as at b;
with a 10 ft. rod, the eye would be about 9 ft. away, as
at c, but there is no difficulty in getting the eye in the
proper line x y, in which the line of sight just cuts the
top of the flame. As the lamp is raised, the operator
steps back a few paces, keeping his eye in that line. The
horizontal distance of the eye from the vertical at the
point c is about 7| ft.

It would appear from the diagram that any elongation
that takes place should be observed at any point along
x y, and this is actually possible. In some of the
experiments made, two observers watched the lamp at
different points, one at b and the other at c. The
spiring of the flame was clearly seen at both points.
The observers then changed places, and equally decisive
effects on the flame were observed.

The tests were carried yet a step further, and it was
found that even with an operator kneeling at d, the
eye being about 12 ft. from the lamp, the elongation was
discerned with certainty every time.

These results should satisfy the most hypercritical as
to the reliability of the normal flame for gas detection,
and justify the use of a 6 ft. staff for the purpose. It is,
of course, often impracticable in the mine, especially in
narrow cavities, to use a rod of much greater length, but
where the conditions are favourable, and the lamp gives
no indication of gas on a 10 ft. rod, the writers maintain

that a fireman has reasonable ground for not reporting
gas in such cavities.

It must be clearly understood, however, that while
the writers advocate the continued use of the ” long-
stick ” method as being thoroughly reliable and
practicable for testing in cavities, they would be among
the last to encourage any laxity on the part of any mine
official. As with every other method, this test is only to
be relied upon when carried out with the greatest care
and with the object of finding gas, if there is any
present. If the general body of the air contains 2 per
cent, of gas, one should not expect to detect 2J per cent,
in a cavity with a large flame, as the best results are
obtained when the air current is comparatively pure, and
the lamp is passed from fresh air into the mixture, but
in an atmosphere of about 1 per cent, satisfactory results
were obtained. The general current must be tested
with the standard testing flame; and if 2 per cent, is
found, the fireman need make no further tests, but
should take steps to dilute the gas.

To show the effects produced by different mixtures,
the series of photographs has been prepared. It is seen
that with 1| per cent, a slight increase of about of an
inch in the height of the flame takes place. This is at
once apparent when the lamp is inserted into the
mixture. Of course, it requires considerable skill, and
good eyesight, to detect the cap produced with this
percentage, especially when using oils of a high flash
point, as it is difficult to distinguish between the gas cap
and the fuel cap, that is, the cap produced by the
volatilisation of the oil itself. It also requires very
favourable conditions to detect the elongation with this
percentage when the lamp is suspended on a rod at some
height. It may be stated as a general rule, however,
that mixtures which produce caps also cause lengthening
of the normal flame.

A graph of the elongations is shown in fig. 3. A
remarkable feature of the curve is the tendency to flatten
between 3J and 5. This is the reverse of what, at first
sight, might be expected, because in the case of gas caps,
the curve rises very rapidly between these points. The
writers, however, venture to put forward the following
explanation of this phenomenon :—In the first place,
the larger flame produced requires more oxygen, and as
with increasing percentages of gas the proportion of
oxygen decreases, there must necessarily be a point on
the curve at which, for want of oxygen, any further
increments in the percentage of gas will not be accom-
panied by any corresponding elongation of the flame.
Experimentally, it is found that 6 per cent, does not
produce a pronounced lengthening, but causes the flame
to flicker for a few seconds; the gas is then ignited in the
gauze, and eventually the oil flame dies out, leaving the
gauze full of burning gas.

MIMING ASSOCIATION OF GREAT BRITAIN.

A meeting of the executive council of this association was
held at the Whitehall Booms on Wednesday afternoon.
The President, the Bt. Hon. the Earl of Crawford and
Balcarres, occupied the chair, and there were present the
following members -.—Messrs. W. C. Blackett, S. Hare and
B. Guthrie (North of England); Tom P. Martin (Cumber-
land) ; F. J. Jones, W. Hay, J. H. Cockburn, B. Bichardson,
W. H. Chambers, E. B. Whalley, C. B. Crawshaw, Boslyn
Holiday and J. Warrington (Yorkshire); Arthur G. Barnes,
G. A. Longden, H. Eustace Mitton, George J. Binns, J. W.
Fryar, J. Mein, Alfred Hewlett (terts), Mark Fryar, J.
Bagnold Smith and Ernest E. Bramall (Midland Counties);
F. A. Grayston (Warwick); Sir J. S. Harmood Banner,
Capt. H. V. Hart Davis, A. M. Lamb, J. S. Burrows,
Ernest Douglas, Vincent Bramall and Tom Stone (Lan-
cashire) ; J. Selby Gardner and William Hill (North
Staffordshire); James Darlington and G. J. Findlay (North
Wales); H. E. Gray, Hugh Bramwell and W. Gascoyne
Dalziel (South Wales); William Bussell, C.B., Bobert
Baird and T.W. Steven (Scotland); Thomas B. Batcliffe-Ellis
(law clerk and secretary) and Arthur Batcliffe-Ellis (assist-
ant law clerk and secretary).

Letters of apology for non-attendance were announced as
having been received from a number of members.

The President announced that the minutes of the last
meeting, having been printed and issued to members in the
60th annual report, would be taken as read and confirmed,
and in this the meeting acquiesced.

The undermentioned principal matters were dealt with :—

Bailway Bills, 1914—Lateral Support for Bailways—
Bescue work in Mines—New Begulations—Explosives in
Mines Order—Coal Mines (Northumberland) Bill—Smoke
Abatement—Departmental Committee—Unemployment In-
surance—Workmen’s Compensation Act—National Insur-
ance Act—Dust Proof Colliery Tubs, etc., etc.

Capt. Hart Davis.

At the conclusion of the business on the agenda, Mr. F.
J. Jones said he had heard with great regret that afternoon
that their esteemed colleague Capt. H. Hart Davis was about
to sever his connection with the Bridgewater Collieries in
Lancashire, and that consequently they were not to have the
benefit of his presence at their meetings after the present
one. He was sure they all agreed that it had always been
a pleasure to be associated with him at their council and
other meetings, and he hoped Capt. Hart Davis would
permit him to convey to him their good wishes, and to say
that they sincerely hoped he would have every happiness in
the years to come although it might not be at meetings in
connection with the coal trade. (Hear, hear.)

The President associated himself with the good wishes
which had been voiced by Mr. Jones.

A cordial vote of thanks to his lordship brought the
meeting to a close.