750

THE COLLIERY GUARDIAN.

Apbil 11, 1913.

roads was apt to do more harm in kinks and abrasions
than would justify any increased protection, apart from
the enhanced difficulty in slinging them satisfactorily in
such a position. To bury roadway cables was un-
doubtedly bad practice, and one such successful attempt
could not justify its adoption.

Mr. Anderson said he particularly welcomed Mr.
Nelson’s contribution to the discussion. The questions
raised regarding rubber were important, and to make
the matter quite clear it might be said that for all main
feeders (both shaft and roadway) installed under average
conditions, rubber-insulated metal-sheathed cables were
unquestionably the best. Their cost, however, rendered
them quite prohibitive for ordinary commercial
purposes. Next in suitability and general efficiency
undoubtedly came bitumen, which possessed many of
the properties which render the use of rubber so
excellent. The writer could not quite understand Mr.
Nelson’s remarks regarding the unsuitability of rubber
for “ tailing ” purposes, and would invite further
discussion from him on this point. It was, of course,
clear that the ultimate desire of the framers of the new
rules was to persuade manufacturers of switch gear to
provide suitable sealing chambers for the cables on their
apparatus, and so do away with tailing cables altogether
—a consummation which would be most heartily
welcomed by the cable manufacturer. Perhaps, if Mr.
Nelson were to substitute the word “ obsolescent ” for
“obsolete,” he would describe more accurately the
present position. .

Under present circumstances where terminal boxes
were provided, the cores of cables going through
them should invariably be cut. To continue through
such boxes with the unprotected paper or bitumen
insulated cores (bifurcated or trifurcated therein) would
be impossible: there remained then only rubber
insulated leads or bare metal. Such rubber insulated
leads provided the necessary mechanical strength.
Under the new rules they were themselves enclosed in a
metal sheath or tube (to a point presumably as near
their respective studs as the tubing can be brought).
The safest method of making them off to the lug, was
to provide the non-fibrous seal mentioned in the paper.
Mr. Nelson’s remarks regarding earthing by plates in
water were interesting and valuable. It should, of
course, be borne in mind that plates thus treated were
not exactly surrounded by water, but were probably
more or less sunk in mud. The efficiency of such plates
would, equally with any other kind, be subject to the
Board of Trade tramway test mentioned in the
paper.

The recent report on electrical accidents where high
resistance in the earth circuit had led to trouble,
abundantly justified Mr. Nelson in the stand taken to
ensure efficient connections to earth, and the writer
could only add that if colliery engineers would armour,
bond, and earth soundly, fatal mishaps below ground
due to electrical causes would practically become
unknown.

New Members.

The following were elected :—As federated members :
Mr. Christopher Kearton, colliery manager, Wingham,
near Canterbury, and Mr. Arnold Lowe, surveyor,
Atherton Collieries, Atherton. As associate member
(federated): Mr. John Ranson, Accrington; and as
associates, (federated): Mr. John W. Case, colliery
fireman, Hulton Park, near Bolton; Mr. Wm. Thos.
Molyneux, colliery fireman, Holly Bank, Bamfurlong;
and Mr. Ralph Gregory, colliery fireman, Abram,
Wigan.

The Minimum Wage and (Fraud.—At Newcastle Moot
Hall, on Wednesday, John Taylor, 35, of 36, Office-row,
Burradon, was charged with having obtained lid. by false
pretences from the Burradon and Coxlodge Coal Company,
on February 25 and 26. Mr. Clark said the case was a
peculiar one, arising out of the Minimum Wage Act. Taylor
was a hewer, and he and five other men worked together as
“ marrows,” two working in each of the three shifts. One of
the places where they worked was a soft place and the other
a hard one, and on the two days named in the charges Taylor’s
“ marrow ” was not down the pit. Taylor went to the hard
place where he would not earn the minimum, but it would
be made up; and he must then have gone over to the soft
place, and worked, and sent in two tokens—one for the tub
filled from the soft place and one for the hard place, at
which he had only worked for a short time. The amount
was of no consequence, but the offence was a serious one.
Everything was being done to enable the miners to earn a
living wage, and he was asked by the owners of the colliery
to point out that they felt it was their duty, not only to
prosecute, but to ask the Bench not to treat the offence in
the ordinary sense of a breach of rules, but as an offence
which, if carried out systematically, would result in
considerable loss. A fine of 30s. was imposed on each
charge.

THE USE OF SQUIBS FOR SHOT-FIRING.
Committee’s Report.

The report of the Departmental Committee on the
use of Squibs for the Purpose of Firing Shots in Naked
Light Mines, appointed by the Home Secretary, has
been issued. [Cd. 6721.]

The committee consisted of Mr. H. Johnstone, H.M.
inspector of mines for the Midland and Southern
Division (chairman), Mr. A. M. Lamb, and Mr. S. Walsh,
M.P., and was appointed on November 7, 1912, to make
enquiry and report with regard to the use of squibs for
the purpose of firing shots in naked light mines, and
particularly as to whether their use is attended with
such special danger as to make it desirable that this
method of firing shots should be prohibited, and if not,
whether any special conditions in regard to the
manufacture and use of squibs should be laid down.

The question chiefly affects the mines in Scotland,
Northumberland, Durham, the anthracite districts in
South Wales, Leicestershire, Warwickshire, and Glou-
cestershire, and evidence was heard from the Coal-
owners’ and Miners’ Associations in these districts.
The Committee now report:—

Description of Squibs.

The form of squib or “ straw ” originally used for firing
shots in naked light mines consisted of a short length of
ordinary oat straw, or a short tube or “ spill ” made by
rolling a strip of paper round the point of the needle or
pricker, plugged at the ends and charged with gunpowder.
The charging was usually done by the miners themselves,
either at their homes or in the mine; and the handling of
the loose gunpowder, usually with a naked light in the
immediate vicinity, frequently resulted in accident. The
charging of the straws in the mine or elsewhere than in a
place licensed for this purpose was prohibited by the
Explosives Act, and such straws became obsolete.

They were superseded by the modern squib, four forms of
which were submitted to us, and may be briefly described
as follow

(1)	The Sulphur Squib, called by the makers “No. 2”
squib, consists of a paper tube about 6| in. in length and
iin. in diameter, plugged at one end and filled for a
length of 4|in. with fine-grained gunpowder. This
portion is coated externally with a solution of silicate of
soda, which serves to stiffen it and keep it in shape, and
at the same time to protect it from damp and to prevent
it from smouldering. The remaining portion is twisted
up tightly and dipped in melted sulphur, thus forming a
" touch” or slow match about 2 in. in length.

(2)	The Saltpetre Squib, called by the makers “No. 3 ”
squib, is similar in every respect, except that the sulphur
is dispensed with, and the slow match is dipped in a
solution of saltpetre.

(3)	The Brock Squib consists of a paper tube 5| in. in
length and in. in internal diameter, plugged at one end
and filled with ordinary gunpowder for a length of 2 in.,
the remaining 3|in. being filled with a fuse composition.
A slow match or “ touch ” made of paper treated with
saltpetre is attached to the unplugged or lighting end.
Between the fuse and the powder the case is choked to
ensure the inward spurt of flame.

(4)	A tube of tinned sheet iron, about 3 in. in length and
| in. external diameter, plugged at one end and filled
with gunpowder, the other end being nipped on to a
short length of ordinary cotton-covered or taped safety
fuse.

The squibs are manufactured in factories or workshops
which are subject to the inspection of H.M. inspectors of
explosives, in so far only as the manufacture and storage
are concerned.

Methods of Using the Squibs.

The shot-hole having been drilled, the charge of powder
is pushed home, and a copper needle inserted, its point
passing through the paper covering where loose powder in
cartridges is used, or through the hole formed in the centre
of the pellets of compressed powder where it is used. Clay
or other suitable stemming is then pushed into the hole
and rammed home, and when the stemming has been
completed the needle is turned or screwed in the hole in
order to form a smooth surface, and withdrawn. The
plugged end of the squib is then cut off or crushed, and
this end is inserted in the mouth of the hole left by the
needle, and in some cases held in position by a small piece
of soft clay. The outer end of the slow match or touch is
ignited, and when it has burned to the powder in the squib,
the flame shoots to the back of the hole and ignites the
charge.

If the slow match is lighted by the direct application of
the flame of a candle or other open light, there may be
considerable risk of the ventilating current deflecting the
flame and causing it to ignite the live portion of the squib,
thus causing a premature explosion. To obviate this, it is
customary to light the slow match by means of a small
piece of touch paper, and in some districts the practice
prevails of nipping off a piece of the slow match of the squib
and using it to convey the flame from the candle to the
squib. The shortening of the slow match in this fashion
necessarily expedites the firing of the shot, but is accom-
panied with considerable danger.

Time of Burning of the Slow Match.

To ensure regularity as far as possible, the paper of which
the cases of the squibs (1) and (2) are formed is cut to a
standard length, but notwithstanding this, experience
appears to show that the time occupied in the burning of
the slow match varies within considerable limits, and is
probably affected by atmospheric conditions, and by the
condition of the slow match as to dryness. Prof. Merivale
(162) suggests “ a minute or a minute and a-half, whatever
it is timed for ” ; Mr. Southern (270) states that “ they are
timed not to burn less than one minute, and are capable of
going a minute and a-half ”; and Mr. Tapson (470) states,
“ it will take about a minute and a-half in burning.” One
of the best known makers informed us that on testing over
50 squibs he found that the match bprned for from 45 to
50 seconds before the squib “ flashed.”

The chairman had 81 sulphur squibs, in normal condition,
tested, and found that the maximum and minimum times of
burning were 130 and 35 seconds respectively, the average
time being 65 seconds. Forty saltpetre squibs were also
tested, and gave maximum and minimum times of 205 and
100 seconds respectively, the average time being 143 seconds.
Fourteen of the saltpetre squibs, the slow matches of which
had been untwisted and partially opened out, were also
tested, and gave maximum and minimum times of 92 and
20 seconds respectively, the average time being 52 seconds.
The tests were made on a wet day, and the moisture in the
atmosphere probably affected the slow matches and some-
what protracted the burning. Messrs. Brock and Co. tested
30 of their squibs (3), and were good enough to communicate
the results to us. The burning of the touch paper was
found to be erratic, ranging between 4 and 29 seconds, and
averaging 12 seconds. The burning of the slow combustion
portion of the squib was, however, remarkably uniform*
ranging between 18 and 21 seconds, and averaging
19 seconds. The total time between the ignition of the
touch paper and the flushing of the squib ranged between
24 and 47 seconds, and averaged 31| seconds.

The time of burning of the fuse attached to the metal
squib (4) will obviously vary with its length and quality,
and may range between very wide limits.

Possibilities of Tampering with the Slow Match.

(1)	The Sulphur Squib—The time during which the
slow match is designed to burn may be considerably
shortened (a) by nipping off a portion of it, (6) by bending
it downwards so that the flame may mount more rapidly,
or (c) by applying the light otherwise than at the outer end
of the touch.

(2)	The Saltpetre Squib.—The above remarks apply
equally to this squib, with the addition (d) that the touch
may be untwisted, in which case the flame may travel more
rapidly along the edge of the paper, and if the “ knot ” at
the inner end of the touch has been rubbed or squeezed,
some grains of powder may find their way into the touch
and cause a premature explosion.

Relative Safety of the Methods of Firing Shots.

The leading evidence on this subject given before the
Royal Commission on Mines by Capt. Desborough, H.M.
Inspector of Explosives, which probably considerably
influenced their conclusion that “ the use of squibs and
straws is open to great objection ” (vide Second Report
p. 122) and their recommendation that such use should be
prohibited (vide Second Report, p. 207), covered only a very
limited period, and dealt chiefly with the risk of accident
from premature explosions. We desired to have the figures
brought up to date, and, generally, to obtain fuller infor-
mation from the Explosives Department, and for this reason
asked Capt. Desborough to appear before us. As, however,
he was engaged on important work at Eskmeals, and as the
Registers of Accidents from which the figures must be
obtained were now kept by or under ths direction of Major
Crozier, we arranged with the Explosives Department that
he should appear instead of Capt. Desborough.

The method adopted in the Explosives Department of
tabulating mining accidents due to the use of explosives is
as follows (Royal Commission’s Report, 39795) :—

(1) Prematures, or failing to get away from the shot-
hole ; (2) electric firing when persons are at the shot-
hole; (3) not taking proper cover; (4) hang-fires and
returning too soon to the shot-hole; (5) boring into or
tampering with miss-fired shots; (6) ramming and stem-
ming; (7) ignitions of explosives by sparks or flme;

(8)	striking unexploded charges in removing debris;

(9)	unintentionally boring into unexploded charges;

(10)	preparing charges; (11) lighting fuses before
inserting the charge; (12) fumes; (13) hot or unex-
ploded residue left in the shot-hole after socketing ;
(14) miscellaneous.

It appears to us to be obvious that accidents classified
under subheads 3, 5, 6, 7, 8, 9, 10,11 and 13 have no distinct
relationship to the method of firing, while those under
subhead 2 affect electric firing only. Those under sub-
head 12 may also be eliminated, as while it was stated to us
by several witnesses that the smoke from a burning fuse was
much greater than that from a squib, and caused incon-
venience where the ventilation was slack, it can hardly be
contended that it gives rise to any danger. The accidents
which chiefly concern our enquiry may therefore be said to
be grouped under subheads 1 and 4, viz., prematures and
hang-fires.