April 9, 1914.

THE COLLIERY GUARDIAN.

787

1.	The machine should he of ample size, so as to
work without undue heating, and the writer prefers to
specify that the machine should carry full load for six
hours with a temperature rise in no part exceeding the
temperature of the surrounding atmosphere by more
than 70 degs. Fahr. The machine should also be able
to withstand an overload of 25 per cent, for two hours
without undue heating, and a momentary overload of
not less than 50 per cent. In many cases machines
will withstand an overload up to 100 per cent, without
injury.

2.	The rotors must be extremely well made, in order
to secure accurate balance, and the writer has a
preference for rotors made from a solid forging, with
slots in which to carry the conductors, secured by
either brass or wedges of suitable material, and with
steel end covers. The rotors should also be so designed
as to admit of free ventilation and thorough cleaning
out, and the attendants should be instructed to see
that the airducts through the rotors and the stators
are kept clean.

The accumulation of dirt in turbo-generators can be
avoided by the use of air filters, and there are very many
satisfactory types on the market.

In specifying generators, it is desirable to know the
electrical details in regard to the voltage rise from full
1 oad to no load on unity and varying power factors, and
the writer strongly recommends the use of automatic
voltage regulators in preference to calling upon makers
to supply machines with a very level characteristic.

Lecture on Explosiyes.—Mr. W. Macnab delivered his
second lecture on explosives at King's College, on Thursday,
March 26. The first of these two lectures, which have been
given under the auspices of the Institute of Chemistry, was
given on February 26, and was reported in our issue for
March 6, p. 515. On the occasion of the second lecture,
Prof. Herbert Jackson presided. The lecture dealt with the
manufacturing side of tie explosive industry, reference
being first made to the restrictions and regulations imposed
on the industry by the Home Office in the interests of
safety. These regulations were, said the lecturer, irksome
in some cases, but the law must be carried out. Before
coming specifically to describe the manufacture of
explosives, a number of lantern slides of various explosive
factories were shown, and the advisability of the use of
wood buildings, which has been questioned in recent years,
was referred to. The use of sand concrete has been lately
suggested, but at present there is not sufficient experience
to pronounce final judgment as to whether this will prove
the most suitable. Another feature of the photographs
was the difference between German and English explosive
factories in regard to the proximity of mounded buildings.
In Germany the practice is to have them much closer than
is allowed in this country. From this the lecturer passed
on to a general description of the manufacture of
explosives, more particularly nitro-cellulose and nitro-
glycerine. Incidentally it was hinted that much informa-
tion is locked up in laboratories for private consumption
as to the manufacture of nitro-glycerine, and never
allowed to become public property. Thomson's displace-
ment process for making guncotton is the most important
improvement which has been made in this branch, and it
has, said Mr. Macnab, the great merit of producing better
guncotton at less cost than the old processes, and at the
same time of being much less unpleasant and dangerous to
the workpeople. Nathan and Rintoul's nitrator separator,
for making nitroglycerine, was next illustrated and
described. Here again progress had been in the direction of
simplicity and safety, one of the features being the abolition
of all cocks in the pipes through which the nitroglycerine
passes. The charge of glycerine which can be nitrated in
one operation has now increased to 1,400 lb. Referring to
the ammonium nitrate class of explosives, which consist
chiefly of two or three non-explosive ingredients mixed
together, the lecturer considered it a distinct hardship and
contrary to the public interest that such explosives should
be penalised by having to be manufactured under the same
expensive conditions as their much more dangerous rivals.
They should be allowed to compete on the market with the
advantage of their inherent properties. The test for “ per-
mitted " explosives was gone into. The filling charge for
shells most generally used in the principal countries is now
trinitro-toluol, which is a safe and powerful explosive. Tetra-
nitroaniline is the strongest known explosive body, and is
also very stable, and would appear to offer any advantages for
torpedoes, military-blasting work, and possibly as a charge
for shells and aeroplane bombs. A model aeroplane bomb
was exhibited. A more pleasing use for explosives was
referred to in connection with agriculture. America and
the colonies have been the chief fields for this development,
but the planting of trees and rejuvenating of existing
orchards by means of explosives would appear to be worthy
of careful study and trial in this country. Finally it was
pointed out that chemistry is the foundation of the explosive
industry, and that the chemist should play the leading
technical role in it. A high standard of conduct and
conscientious carrying out of work are necessary, seeing
that carelessness or a mistake may endanger or sacrifice the
lives of many people.—A very hearty vote of thanks was
accorded the lecturer at the conclusion, on the motion of
the chairman, who mentioned that he remembered experi-
ments in the lecture room, during which the windows had
been blown out.

SOUTH WALES INSTITUTE OF ENGINEERS.

Standardisation of Tin-plate Plant.

The 56th annual general meeting of the South Wales
Institute of Engineers was held at the Hoy al Jubilee
Metal Exchange, Swansea, on March 31, Mr. Henry
T. Wales, the president, in the chair.

The following new members were elected:—John
Auld, locomotive superintendent, Barry Bail way ; A. J.
Burn, Llanmore Works, Llanelly; C. H. Goulden,
Cardiff; W. Rees Griffiths, Neath; A. E. Howell,
Newport, Mon.; E. W. Morgan, colliery proprietor,
Abercrave, Brecknockshire; H. W. Morgan, M.A.,
St. David’s Tin-plate Works, Loughor : Morgan W.
Morgan, colliery proprietor, Abercrave ; W. E. Morgan,
Princess Royal Collieries, Lydney; T. Llewellyn Mort,
Treherbert; T. A. Parry, Saundersfoot, Pembrokeshire;
and W. Rhodes Ward, A.rmley, Leeds.

Lewis Prizes/|1914.

The President announced that the council had
chosen “ How to Improve Welsh Tin-plate Rolling Mill
Practice ” as the subject of the competition for the
Lewis prizes of £25 and £10, all papers to be addressed
to the secretary of the institute before December 31,
1914.

Some Notes towards Standardisation of Tin-plate Plant.

Mr. H. Spence Thomas, Melingriffith, read a paper
drawn up by Mr. Fred J. Taylor, Briton Ferry, and
himself, advocating the standardisation of many details
of plant used in the production of tin-plates, and the
appointment of a committee of manufacturers to this
end.

The authors considered that it would be quite
impossible to standardise prime movers, and the
standardisation proposed was more particularly in
regard to the details that had to be renewed from time
to time through wear and breakage. Amongst these
were mentioned bar-cutters, plating and doorways of
mill furnaces, fireplace castings, boshes for millmen,
stands for tin bars, bedplates (flat bottom and V-type),
standards, screws and boxes, rolls and necks, wobblers,
fast and loose crabs, doublers, shears, connecting
spindles, drives, cradles, annealing pots and stands, &c.

In the discussion that followed Mr. F. W. Gilbertson
said with the growth of foreign competition it behoved
Welsh tin-plate makers to stand together and do all
they could to help each other in meeting competition.
There was no doubt the absence of standardised plant
parts involved an expenditure of capital which should
go in the development of business, and representatives
of engineering firms who supplied these parts should
come together and indicate what were the parts which
in their opinion admitted of standardisation.

Mr. J. A. Davies (Cwmfelin) said the difficulty in
the past to bring about a standardisation of plant was
that so many interests were involved in the tin-plate
trade, but in these days there appeared to be a desire on
the part of engineers and manufacturers to act together
for the common good, and for the general protection
and advancement of the Welsh tin-plate industry. If
they were to successfully meet outside competition and
retain their markets, more must be done to cheapen
production, and it was in the direction of economy that
uniformity of plant must tend.

Mr. John Williams (of Clayton) said there was more
being done in the direction of standardisation in the
Welsh tinplate trade than was the case formerly. He
was convinced that more could be done on the lines
suggested in the paper.

Capt. T. O. Edwards, factory inspector, urged the
adoption of standardised fencing for machinery at the
tinplate works.

Mr. Collins, of the Phosphor Bronze Company
Limited, London, said his company would certainly
welcome anything in the shape of standardisation of
plant that would enable the makers of the plant to give
a quick supply.

Mr. Hilditch, H.M. inspector of factories, said pro-
vision for fencing machinery in tin-plate works seemed
to be lost sight of in the initial designing of the
machines, with the result that much labour was subse-
quently entailed in drilling and cutting out holes for
the reception of stanchions which might easily have
been made in the original casting. The standardisation
of fencing should be included in the programme of the
proposed committee.

Mr. Morris (Baglan Bay) said it was the foundrymen
who ought to start standardising—the makers of the
castings.

Mr. David E. Roberts (Cardiff) said it had often
been a subject of wonder to him why in such an industry
as the tin-plate trade, with comparatively few set sizes
of plates to turn out, there was such a variation in the
heavy plant employed. The speaker gave some
interesting details concerning the lay-out and manning
of tin-plate works in the United States.

Mr. Fred J. Taylor attributed the fact that foundry-

men had so many different patterns on hand to the
frequently-exposed wish of the tin-plate maker that
plant should be designed on lines which he himself laid
down.

The authors of the paper were thanked, and the
proceedings terminated.

THE LOW FIREDAMP INDICATOR.

Various devices have been designed to give an
immediate warning of the presence of an explosive
mixture. Many of these, however, have been sensitive
to heat, and, to avoid their giving a false alarm under
these conditions, they have had to be adjusted coarsely,
so that it required a considerable escape of gas to
operate the alarm correctly.

The Low gas indicator operates upon a very well-
known principle, and yet is constructed so that it is only
affected by an escape of gas. The principle of the gas
lighters, in which a thin platinum wire becomes white
hot in the presence of coal gas, is well known, and it is
on this principle the little instrument works. A
chemical compound of spongy platinum, specially pre-
pared in flakes, is employed.

The diagram shows the means of operation. There
are two wires, one P of thin platinum, with a few small
balls of spongy platinum attached to help its heating
properties under the influence of gas, and the other wire
is half of iron F and half of brass C, having the same
coefficient of expansion as the platinum wire placed
beside it.

A spring is arranged to tend to stretch the platinum
wire relatively to the iron, and a contact R is fixed, so
that by the sagging of the wire, as well as by the multi-
plying gear of the needle, the instrument can be made
exceedingly sensitive to any change of temperatures of

the platinum wire. It will be seen that this instrument
is extremely ingenious, because the whole apparatus can
be operated opposite a furnace without giving the alarm,
as each wire stretches by exactly the same amount.

If the two wires stretch together this is taken up by
the spring S, but when one stretches without the other
the alarm is given. Needless to say, the wire never can
become more than warm, even if impure gas. The least
escape of gas or other explosive mixture will heat the
platinum wire more than the other; thus, the difference
in expansion will immediately cause the alarm bell to
ring, quite apart from the temperature, or from other
considerations.

The whole apparatus can be made circular, as' small
as 2 in. in diameter, by winding the wires round an
insulator, but it is shown in the diagram with the wire
at its full length for clearness.

These instruments may be fitted in the various shafts
and worked separately, or connected with a numbered
indicator board placed in a convenient position above
ground. It is the invention of Dr. A. M. Low,
A.C.G.I., D.Sc., and is made by the Low Gas Indicator,
15, Great St. Helens, London, E.C.

A Bill has been brought in by Mr. Bowerman to amend
the provisions of the Trade Union Act Amendment Act,
1876, in relation to the amalgamation of trade unions. It
provides tha any two or more trade unions may become
amalgamated together in one trade union, with or without
any dissolution or division of the funds of such trade
unions, or either or any of them, provided that no such
amalgamation shall take place except with the consent of
two-thirds of the members of such trade unions voting on
the question whether or no such amalgamation shall take
place. The decision of the members shall be ascertained by
ballot, and every member shall have not less than 14 days'
notice of the taking of the ballot, and the question to be
resolved thereby, at the central or branch offices of such
trade unions, in accordance with regulations to be made by
the executive councils of such trade unions,