October 22, 1915.

THE COLLIERY GUARDIAN.

823

Mr. W. H. Hepplewhite (H.M. inspector of mines)
moved a vote of thanks to the president for his address,
which, though short, had touched upon several points of
great importance.

Mr. G. Spencer (West Hallam), in seconding, said
that they ought all to take to heart the president’s
advice, and devote special care and attention to pre-
paring themselves for what would come when the war
was over.

The resolution having been cordially adopted, the
President replied. ' ,

The Late Mr. J. W. Fryar.

The President briefly referred to the death of Mr.
J. W. Fryar, and intimated that the council had taken
the earliest opportunity of forwarding a vote of con-
dolence to his relatives, who had suitably replied.

The Support of Coal Roofs.

It was decided to discuss together Mr. W. H.
Hepplewhite’s papers on “ Substitutes for Wood
Supports of the Roof in Longwall Work ” and “ The
Action and Control of Differently Constituted Coal
Roofs,” and Mr. Frank N. Siddall’s paper entitled
“ Some Notes on Supporting the Roof in Coal Mines.”

Mr. W. A. Machin (Birmingham) remarked that the sub-
stitutes for wood which had been mentioned possessed the
following disadvantages, amongst others :—First, they were
not adjustable to the varying heights of the seam; and,
second, they were difficult and dangerous to withdraw from
the goaf, for they had either to be loosened underneath or
over the top, according to the nature of the roof or the floor.
A few advantages of using steel supports were :—First, the
props were regularly set and withdrawn ; second, the packs
were put in as the face advanced, and the work had to be
done at the proper time, in order that the supply of props
might be maintained; third, the roof weight was better con-
trolled, subsidence taking place regularly in the goaf, keeping
the weight off the face; fourth, it was easier (owing to the
greater strength of steel props) to induce a line of break in
the roof, which was a great advantage in withdrawing the
supports, because the workmen knew exactly where the roof
would break; and fifth, unlike wood, they would not cause a
gob-fire. He mentioned this because in some districts com-
panies went to great expense to withdraw all the timber in
seams liable to spontaneous combustion. He had seen wood
props charred when driving through gobs in seams where gob-
fires were unknown. Mr. Machin then proceeded to give some
particulars of a patent adjustable steel prop, which was in
use at collieries in Staffordshire, Nottinghamshire, Yorkshire,
and Scotland, and was manufactured by the Atlas Mining
Outfit Company, of Willenhall, Staffordshire—an actual prop
being exhibited to illustrate the speaker’s remarks. The prop
consisted of a steel or wrought iron tube, steel springs, and a
cast steel head, with nut which revolved round the top of the
tube. The tubes were 3 in. outside diameter, and | in. thick
for props up to 5 ft. 6 in. long, above which they were 3J in.
diameter. The spring was fitted into a metal foot-piece, and
fastened by a bolt. When pressure was exerted on the prop
the bolt kept the spring in a vertical position. The head was
made in three types—rail-head for bad roofs, notched-head for
good roofs, and large rail-head for main roads and for tem-
porary use when resetting wood legs which were set under
girdles. The rail-head type had a special recess to receive a
bar or rail, and was of such a shape as to permit the bar
being tightened or loosened from the roof while the prop was
still under pressure. This was effected by means of a cotter
passing through the head of the prop. The setting and with-
drawal was easily accomplished by means of the nut, which
revolved at the top of the tube. A lid was placed on the top
of the prop. As the coal was removed, the rails were alter-
nately slackened in the recess head, and then advanced
towards the coal face, the props belonging to each rail sup-
porting the roof of that particular area, though temporary
props could be set if needed. The notched-head props were
set in the same way as ordinary props. The spring at the
foot was used to allow the roof gradually to subside, and it
would give about 3 in. at a pressure of seven to eight tons.
When the spring was fully compressed, the prop should be
slightly released by means of the nut to ease the weight of the
prop, allowing the spring to do its work. In some tests
which were made with a pressure up to 30 tons in the case of
steel, and 31 tons in the case of wrought iron, only the tubes
were bent, the other parts being quite intact. Afterwards
some of the tubes were partly filled with concrete, and tested
at pressures varying from 30*712 tons for a 3 ft. 10 in. prop.,
to 37-409 tons for a 2 ft. 3 in. prop, with the result that while
the tubes were bent, the other parts were unaffected. Separate
tests were then made of the nut and screw, and it was found
that they were bent badly when subjected to a pressure of
47 tons 4 cwt. 3 qr. The screw when tested alone broke at
51 tons 13 cwt. 2 qr.

In reply to several questions, Mr. Machin said that the
cost of a prop 5 ft. 6 in. long was 21s., and the weight,
excluding the head, 101b. per foot.

Mr. Spencer asked if it was an English invention.

Mr. Machin replied that the principle of it was a German
invention.

Mr. W. H. Hepplewhite said that Mr. Siddall, in his
paper, had, of necessity, been compelled to travel partly
over the same ground as was dealt with in the other papers,
but there were several points upon which he would like
to offer a comment. Mr. Siddall seemed to recommend the
use of electric safety lamps by colliery managers in going
their rounds. He (the speaker) would have no objection
to someone walking in front of him with an electric lamp,
but he would like to have an ordinary safety lamp in his
own hands. Mr. Siddall said, “ No prop ought ever to
be set without a lid that is at least in every way larger than
the prop it has to fit. Thickness of the lid does not matter
so much.” He (Mr. Hepplewhite) thought that he was
altogether wrong in that. He believed that it was very
necessary to get a good lid on, and the thicker the better,
because, it took the pressure off the prop, and so helped to
preserve it. Lower down, Mr. Siddall advocated the timbers
being kept in a straight line at the face. Of course, if the

face were kept in a straight line, the timbers would keep
in a straight line as a natural sequence. The difficulty was
to keep the face straight, 'because they had better men in
one stall than another, and the progress was not uniform.
With reference to the use of “ catch ” props, it was highly
essential that they should be set properly. Workmen had a
propensity for putting up ‘ ‘ catch ’ ’ props in a rather careless
fashion, as not being of much importance, and in the
Warwickshire district they had two nasty accidents through
the faulty setting of “ catch ” props. Mr. Siddall strongly
advocated the use of tapered props, and in the colliery where
he was brought up he bad certainly had a good deal of
experience with them. He (the speaker) had been hammer-
ing away for a good many years about the use of tapered
props where the conditions were suitable, and one or the
results of the war had been to cause managers to look round
and see how their timber could be utilised to the best
advantage. One of the best ways was to taper every prop
which went down the pit, provided that the conditions were
favourable. Mr. Siddall mentioned a case where a face
400 yds. long was timbered with tapered props, and there
was not a single broken prop anywhere, while the timber
cost had been reduced 50 per cent. In the pit where Mr.
Siddall was engaged in his early days they used very long
timber—6 ft. to 7 ft. long—and no doubt they did save a
great deal of money, though 50 per cent, certainly seemed
a remarkable sum. If, however, the practice of destroying
a piece of a prop in order to save the rest were adopted
all over the country the saving would be enormous. The
timber bill of the whole country came to something like
.£3,000,000 per annum, and if they could save 50 per cent,
of that, it would be a very big sum. But supposing that
they could save only 25 per cent., or even 15 per cent, of
the present timber bill it would be a highly important
economy. He (Mr. Hepplewhite) was much obliged to Mr.
Orchard for the complimentary references to himself in the
matter of having drawn the attention of the mining com-
munity to the importance of tapered props. Some reference
was made in Mr. Siddall’s paper to concrete props, and
he (the speaker) had had some particulars given to him by
a member who was using them. The total cost, including
cement, washed granite, cracker dust, old wire rope, and
labour was 38s. per 30 props,, which worked out at about
2’3d. per ft. These props were being largely used in
Warwickshire on the main roads, but not so much at the
coal face. If used at the face it was customary to employ
them in conjunction with timber. The props were particu-
larly useful in the return airway, where the humidity of
the atmosphere played such havoc with the timber. If they
took 8 ft. props 8 in. in diameter, the cost of concrete props
was Is. 9d.; props of English timber (at Is. 4d. per cu. ft.),
3s. 8d. ; and props of foreign timber (at 2s. 3d. per ft.),
6s. 3d. The cost of sawing up the English timber was 5d.
per dozen for all lengths. One of their Warwickshire
members had made for him the drawing which they saw
before them of a prop fairly extensively used at the coal
face. As they would see, it was a tubular prop, with the
lower end fitted to hold a piece of timber which was tapered,
and which was sawn out of old lengths of timber at the
pit top. The inside of the prop was filled with concrete of
the following mixture :—Three parts | in. granite chippings ;
one part of sand, or flue dust; and one part of cement.
There were several hundred in use, and some of them had
been set thirty or forty times, and not one had been lost.
Before the war, when foreign timber only was used, the
timber costs worked out at 6*47d. per ton. During the first
six months of the war, when they used some English timber,
the costs jumped up to 10’5d. per ton. Latterly they had
used English timber in large quantities, and steel props, and
the cost had gone down to 7’3d. All the figures were
calculated on the sales tonnage.

Mr. G. Spencer asked if there was any difficulty in with-
drawing the prop?

Mr. Hepplewhite said that there was no more difficulty
than in the case of an ordinary prop.

Mr. Spencer thought that if the bottom of the prop got
surrounded by gob material, the projection on the sides would
cause it to bind, and the bottom would have to be cleared
before it could be withdrawn.

Mr. Watkins asked if Mr. Hepplewhite had seen the
“ Wragg ” prop. It was the invention of a practical man,
and the principal feature was the introduction of two blocks
of wood at the top to take the pressure. These blocks could
readily be split by an axe when the prop was required to be
withdrawn.

Mr. Hepplewhite said that he had not seen the prop, but
could understand how it worked. He thought the difficulty
about it would be that if the weight came on unevenly the
prop would be liable to cant over.

Mr. Spencer remarked that the men would be exposed to
danger when they were engaged in splitting the blocks of
wood. He did not think that the risk of canting over would
be great.

The discussion on the three papers was then closed.

Davis’s Non-Cumulative Winding Engine Signals.

A set of this apparatus was on view, and a paper
descriptive of its construction and working was read by
Mr. Ashby. This was practically the same as the paper
read by Mr. Wilfrid H. Davis before the North of
England Institution of Mining and Mechanical Engineers
(Trans. Inst. Min. Engin., vol. 49, 1, p. 154; Colliery
Guardian, February 19, 1915, p. 385).

Mr. Ashby also described the “ Davis-Derby ” level
indicator designed for shafts where more than one level
or inset is worked. The indicator dispenses with multiple
aural and visual indicators in the engine house, and so saves
complication and expense for a shaft with several levels or
insets. One banksman’s and one onsetter’s, indicator only
are required in the engine house, no matter how many
levels or insets there may be. No extra switches are
required, and only one extra wire is required to each level
or inset. Though primarily designed to work in conjunction
with the Davis visual indicator, the device is an arrange-
ment which simplifies the construction of the last-named,
as the whole of the relays are then carried to the level
indicator. The apparatus is entirely self-contained, and
can thus be put in service in conjunction with any electrical
system of visual signalling, or be installed as an entirely
independent apparatus. The arrangement consists of an

electric magnet for each level, which has a winding on its
core to correspond with the number of levels, in addition
to its own winding. The magnets have therefore each four
windings for four levels connected as three, and one to the
opposite poles. The indicator is mounted on a pivoted
shaft, the lower end of which carries a permanent horse-
shoe magnet, which is, of course, attracted or repelled, as
the case may be, according to the windings in circuit on
the electro magnet. When a signal was transmitted from
any one of the four levels, the relay is operated on that
circuit which connects through the battery to the indicator,
forming a circuit, and attracting the permanent magnet;
and thus bringing into the visual position the flag indicating
that particular level. At the same time, the current passing
through the coils of the other electro magnets, repels the
horse-shoe magnets, and cancels any previous indication.
Obviously it is impossible for more than one flag to be in
the visual position at once. Normally, any level indicated
would be cancelled by the next succeeding one, though,
where desirable, provision might also be made for clearing
the indicator from the winding engine.

Several questions were asked, and the President
having thanked Mr. Ashby for his explanations, the
meeting closed.

SWEDEN AND THE COAL QUESTION.

An interesting article on the coal question appears in the
Journal of the Swedish Chamber of Commerce in London.
It is stated that the total imports from all countries of coal
and coke into Sweden for the first six months of 1915
amounted to 2,242,905 metric tons, as compared with
2,134,508 metric tons in the corresponding period of 1914.
There has thus been an excess import of 108,397 tons. A
casual observer may say that the needs of Sweden have thus
been amply met, but it must be taken into consideration,
before a judgment is passed, that the strain put upon the
Swedish railways for transport of transit goods, for the
carrying of refugees, transportation of returned prisoners
of war, and the increased activity in the Swedish industry,
which in many branches has been called upon to fill the
gaps caused in countries involved in the war, all entail
increased coal consumption. It will then be apparent that
this insignificant increase of 100,000 odd tons has not
sufficed to meet the needs.

Mr. Alf. Larson, a prominent Swedish engineer, deals
with this question in Industritidningen Norden. He states
that in 1897 the consumption of coal and coke in Sweden
aggregated 2,524,000 tons, and in 1913, 5,763,000—an
increase of 3,239,000 tons, equalling 128 per cent. The
average coal consumption for the period 1861-1865 was
92 kilogs. per head of population p.a., which figure reached
865 kilogs. for the period 1906-1910, and 1,055 for the year
1913. Mr. Larson writes : “ Our industries will undoubtedly
continue to need fuel in a large degree, in spite of the rapid
strides made in the utilisation of water power. The needs
of the large iron works now building at Oxelosund will
alone increase the coal imports by about 125,000 tons p.a.”

The decrease of export of coal from the United Kingdom
to Sweden during January-June this year amounted to
176,025 tons. This stringency on behalf of Great Britain
is still more marked for the single month of July, when
a shortage of 291,967 tons is registered as compared with
the normal figure. Sweden was thus in the early summer
face to face with a critical position. Then Germany gave
a helping hand in allowing 600,000 tons of coal to be shipped
to Sweden, and American coals were also imported to
counteract the short supplies from the chief supplier—
England. We find that the reduced supplies from the
United Kingdom to Sweden explain the increased exports
to Denmark and Norway. The following are the figures
tor January-June :—

1915.	1914.

Exports to:—	Tons.	Tons.

Sweden.................... 1,628,068	...	1,800,093

Norway ................... 1,359,295	...	1,247,501

Denmark................... 1,537,240	...	1,389,551

4,524,603 ... 4,437,145

These figures speak for themselves, and show clearly that
Norway and Denmark have been favoured at the expense
of Sweden.

The solving of the coal question, or, let us say, the fuel
problem, is thus of vital importance to Sweden, and signs
are not wanting that strenuous efforts are now being made
in that country to safeguard its supplies. An enquete, says
the Journal, on the question of economy instituted by the
Industrial Association of Sweden has just been published
by them (“ Bransleekonomi under kristiden ”) and this little
book throws much light on the subject. It is clearly stated
therein that many important industrial works have already
contrived to do without English coal or with less quantities
than usual. The following substitutes or methods have
been adopted :—

1.	The use of Swedish coal, either solely or mixed with
33 to 50 per cent, of English coal.

2.	The use of coke.

3.	The use of peat, either solely or mixed with coal.

4.	The use of wood, wood waste and charcoal.

Many other works have also increased their electric supply.
Other devices have besides been pressed into service.

It is stated that the best quality of Swedish coal (from
Scania) is useful in an equal degree as the Scotch coal.
According to Dr. Edward Erdmann, the Scania coal deposits
are calculated at 106,500,000 tons. These will now be
developed at the instigation of the Government. But other
home resources will be utilised with a view of making
Sweden to the utmost extent independent of foreign coal.
The enormous peat bogs are being scientifically converted
into fuel. Among the latest additions to this industry the
following will be noted : A factory for the manufacture of
peat, powder, and briquettes at Fristad, Westergotland
County, the raw material to be supplied from a bog with
a depth of 8 m. (about 25 ft.), and the work will be carried
on by double shifts, day and night. Another factory
is the Stafsjo factory (Smalands County) just com-
pleted, where peat briquettes according to the de Laval
process will be manufactured. In conjunction with this
subject, it is interesting to record that a Swedish locomotive
adapted for peat fuel was recently used for the royal trains
which took King Gustaf to Motala when he visited that
town.

Undoubtedly the present policy of Great Britain has
brought this question most forcibly before the Swedes, and
they have not been slow in putting their technical skill and
resourcefulness into full play.