914	THE COLLIERY GUARDIAN.Arau. 30, nils.

CURRENT SCIENCE

Composition and Qualities of Coal.

In the botanical laboratories of Harvard University,
Mr. E. C. Jeffrey has spent seven years in studying the
nature of coal, and some of his results are now published
in a paper in- Economic Geology, vol. ix., No. 8. He has
used the latest methods of thin sections, as originally
carried out in a research on “The Nature of Some
Supposed Algal Coals,’ published in 1910 (Am. Acad.
Arts and Sci., vol. xlvi., No. 12). The author believes
that the micro-study of coal structures supports the
allocthonous or transport hypothesis, rather than the
autocthonous or in situ hypothesis of coal formation.
He shows the resemblance between certain coal
structures and those found in modern lacustrine
accumulations. The “ coal balls ” so commonly found
in European coalbeds show evidence of a similar origin.
The author calls attention to the occurrence of carbo-
nised wood in the Jurassic coal, from Brora, in Scotland,
in which alternations of glance and matt layers
precisely resemble the structure of a piece of Illinois
coal of. carboniferous age.

The interesting deposit of carboniferous age in
Tasmania, known as tasmanite, is an almost pure spore
coal. There has hitherto been some doubt as to the
origin of such bodies in boghead cannels, and some
have attributed them to the remains of gelatinous algae ;
but the author believes that his improved methods of
preparing micro-sections now establishes the fact that
these bodies are thick-walled spores of fern - like
plants. The ordinary cannel coals show light bodies,
believed to be collapsed spores, and darker woody tissue.
The highly bituminous coal of Kentucky shows bright
and crinkled bands of woody substance, separated by
dull canneloid layers composed of flattened spores.
Usually the lignitoid substance predominates, but even
in lean non-coking coals, apparently bright and shiny
throughout, the microscope reveals traces of spores or
canneloid matter. The author has been able to
examine a large number of coals of all ages, and
from most of the coal-producing countries of the world,
and he considers that all coals can be regarded as made
up of three constituents—viz., spores or canneloid
substance, woody tissue or lignitoid substance, and
carbonised matter, mineral charcoal or the so-called
“ mother-of-coal.” Further, he maintains that the
relative proportions of these constituents determine the
properties of the coal. Nothing is said in the paper
regarding the resinous constituents of coal, upon which
so much importance has been placed by recent
investigators.

Protective Devices Against Lightning and Surges.

In a paper read before the Association of Mining
Electrical Engineers, recently, E. Kilburn Scott and
L. F. Fogarty exhaustively deal with a subject which
has received less attention than it deserves, i.e., the
problems encountered in dealing with lightning and
surges of electric current. It is pointed out that as it
is impossible to set up in the experiment the actual
conditions encountered in practice, the usual methods
of testing are not applicable, and all that can be done is
to try the various devices in practice and collect the
results of experience. The authors describe in detail
the different types of arresters that have been used.
Arresters which automatically connect the circuit to be
protected with the earth when an excess voltage occurs,
by means of a spark Jumping across’ an. air gap are
known as spark gaps. Another type of device is the
electrolytic arrester, which depends for its action upon
a film of hydroxide of aluminium, deposited by an
electrolyte on aluminium plates; when the pressure
reaches a critical point the film breaks down innumber-
less minute punctures, which automatically seal up as
soon as the normal pressure is restored. Water-Jet
arresters, or water-leaks as they are sometimes called,
are really resistances used for conducting static charges
continuously to earth. The resistance is formed by
water Jets which flow from earthed outlets on to suit-
able electrodes connected with the high-tension lines.
Resistance arresters are most suitable for low-voltage
mains in which the spark gaps of the arresters provided
are always non-sensitive. Another protective device is
the choke coil, which may be inserted in front of the
machine to keep the voltage surge back until its energy
has been absorbed by a resistance or other device.
Amongst the further appliances that come under this
category are charging switches, which are useful for
starting large three-phase motors ; it is also useful to
connect an arrester between the neutral point of the
motor winding and earth. A device specially dealt
with is the Giles electric valve ; this does not act during
the whole period but only during the time in which the
surge tension occurs, and its effect is to cut off from the
voltage curve all the peaks which are beyond the value
for which the gap is regulated.

Speaking generally, surges in electrical installations
may be set up by:—(1) Atmospheric disturbance,
divided into (a) static charges, (&) high-frequency surges,
and (c) steep-fronted waves of high potential; (2)
defective switching, viz., (d) inexpert paralleling of
alternators, (e) operating badly-designed protective gear,
(/) sudden breaking of a short-circuit by automatic
switches, and ($) switching full voltage on to long cable
lines. The authors consider that breakdowns of appa-
ratus, protected by spark-gap devices, are often due to
the propagation of high-frequency surges of a voltage
which is too low to operate the gap. Horn spark-gap
arresters may themselves set up high-frequency currents.
There has lately come into use a system embodying the
use of condensers of the Moscicki type.. The most
usual method of installing these condensers is to insert
a choking coil between the overhead conductors and the
machines or plant to be protected, and to connect the

AND TECHNOLOGY.

condenser between the choking coil and earth in such a
way that any high-frequency oscillations tending to
propagate themselves into the station would be reflected
back on to the line and earthed through the condenser.
Such condensers are also of considerable use as a
protection against surges due to switching.

Coal Fields of Central Canada.

The Department of Mines of Canada has issued a
revised edition, by D. B. Dowling, of the Geological
Survey Memoir No. 53, dealing with the coalfields of
Manitoba, Saskatchewan, Alberta, and Eastern British
Columbia. The geological formations of this area
include strata ranging from devonian to tertiary age.
Coal occurs at three separate horizons, viz., in the
lower cretaceous or Kootenay beds of Alberta, in the
Montana, and in the Edmonton groups of the upper
cretaceous and early tertiary. Particular interest attaches
to the latter deposits. At the close of the cretaceous
period in this area there was a marked emergence of
land from the sea ; but there appear to have been many
periods of oscillation between land and shallow water
conditions, when the surface remained near sea-level.
It was during this phase that the coal-bearing beds were
deposited. The well-known Laramie stage is partly
correlated with this Edmonton group of Alberta, only
the upper part of this stage being ot eocene age. The
character of the coal deposits varies with the age of
formation, the amount of covering deposit, and also with
the disturbances which they have undergone. Thus the
Kootenay coals, being the lowest and covered by a
greater load, are generally of higher grade, but owing
to local disturbance they vary bet*een coking coals to
anthracites, the latter being predominant in the Cascade
basin, especially near Banff, where the greatest alteration
has taken place. Similarly, the Belly River coals of
Montana a^e vary in quality between coking coals in the
disturbed belt to lignites in the undisturbed area. The
Edmonton coals are often poor lignites with 20 per cent,
of moisture, but are nearer the character of true coals
in the disturbed area. The disturbances, while improving
the character of the coal, has also curtailed the extent of
the coalfields owing to truncation of folds; this is
especially evident in the Cascade area. Several interest-
ing problems arise respecting new developments. Thus,
prospecting is active. southward from the Crow’s Nest
field. Little also is known as yet of the continuation of
the Belly River coals beneath the plains. A point with
regard to the Edmonton coals is the extensive area of
their deposition and the uncertainty of the thickness of
the seams, making it impossible to estimate the total
resources of this deposit. The memoir concludes with
a valuable series of analyses of Canadian and United
States coals.

United States Bureau of Mines.

The report of Dr. Joseph A. Holmes, director of the
United States Bureau of Mines, on the operations of the
Bureau during 1913-14, as usual, contains much of
interest to British mining engineers. Perhaps the most
important accomplishment during the year was the
evolution of four types of barriers to be used in conjunc-
tion with stone dust; these devices, which may be
termed box, concentrated, ventilation door, and ventila-
tion-stopping barriers respectively, have already been
dealt with to some extent in papers read by Mr.
George S. Rice, and reprinted in our columns. These
are now to be tested (a) with various percentages of gas
in the ventilating current, and (b) in complex explosions
throughout more extensive workings. The Bureau
engineers have found, in connection with the coal dust
experiments, that propagation of flame was not obtained
when the percentage of combustible matter in the
mixture throughout the explosion zone was only 35 to
40 per cent., but when a strong explosion was started in
a coal dust ignition zone the flame would travel through
a mixed-dust zone beyond, unless the proportion of
combustible matter there was less than 20 to 25 per
cent. The advantage of water-spraying is, nevertheless,
recognised, and further experiments are to be carried
out; in particular, it has been found that pure coal
dust which is not readily watered loses its repulsion for
water when mixed with shale or limestone dust.

The Bureau has continued to do useful work in the
field in connection with rescue operations following
explosions. Four great explosions occurred during the
year, 263 men being killed in the Stag Canyon Mine, at
Dawson, N. Mex., and 181 at Eccles, W. Va. In these
and other accidents which were investigated, causing a
total death-roll of 585 persons, seven men were rescued
by Bureau of Mines men, 63 by others, whilst 191
escaped unassisted. In the rescue and recovery work
following these accidents, there was a total of 175
persons who wore mine-rescue breathing apparatus. In
the relatively short period during which the crews of
the Bureau’s cars and stations were able to conduct
active training, 46,694 miners visited the cars and
stations, 28,229 attended lectures and safety demonstra-
tions, 2,826 were given mine rescue and 5,780 first-aid
instruction and training, and 3,772 certificates were
issued. In four years 24,975 miners have been trained.
Tests of rescue apparatus have also been carried out,
principally with the object of devising a lighter appa-
ratus to meet the requirements of the miner under
violent exertion.

Amongst the other coal mine investigations continued
during the year were those concerning mine fires, waste
in working, undercutting machinery, explosives, mine
subsidence, and timbering, but Dr. Holmes states that
the work has been greatly hampered by lack of funds
and the preoccupation of officials in other directions.

Another branch of the Bureau’s activities lies in
the fuel investigations. Experience gained from the
inspection of fuel purchased by the Government indicates

desirable changes in the direction of simplification and
reduction of cost in sampling, and improvements in this
connection were made during the year. It is stated
that the success of the specification method of purchase
now rests almost entirely on sampling.

Portable lamps have absorbed by far the greater
portion of the time of the electrical engineers attached
to the Bureau. As a result, two lamps have been
approved. More recently an investigation has been
started regarding the ignition of coal dust by electric
flashes. It is stated that already valuable results have
been achieved, ignitions having been obtained under
practical underground conditions with currents of
surprisingly low voltage.

THE GERMAN AND AUSTRIAN COAL
AND IRON TRADES.

We give below further extracts from German
periodicals that have reached us, showing the course of
the coal and iron trades in Germany and Austria:—

Renewal of the Westphalian Coal Sy dicate.

According to the Cologne Gazette, the endeavour of
the Syndicate to come to an understanding with the
outsiders has met with serious difficulties, so that the
negotiations have made but little progress. On the
other hand, it is stated that an agreement, in point of
principle, has been arrived at with the administration
of the State mines, whereby the latter are to join the
Syndicate and receive an allotment, which has been
fixed and on which the same percentage contribution is
to be levied as is paid by the otlnr members. Negotia-
tions are also reported to be in progress for the
nationalisation of the Hibernia Company, through the
acquisition by the State of all the shares held by the
Hibernia G.m.b.H. In other respects matters are still
as they were, and a number of the large outside firms
seem to think the occasion favourable to secure special
advantages for themselves, irrespective of the general
weal. Under these attempts the idea of a community
of coalmining interests is relegated to the background.
Thus, one of these outsiders has sold the output of two
of his pits for several decades ahead to a company, also
owned by himself, and now desires, in his covenantable
allotment in the Syndicate, to discount the possible
future output of these two pits How an agreement is
to be concluded on these lines is difficult to imagine,
since the Syndicate cannot agree to any terms which go
beyond the limits of the principles of the new draft
agreement and current practice without opening up the
way to fresh demands by other pits. In fact, several
have already announced that their attitude will be
guided by the result of the negotiations with the out-
sider in question. Moreover, difficulties still exist with
the Rom bach Company regarding the treatment to be
accorded the Concordia A.G.; and another group, which
acquired a colliery some time ago, wants to discount now
the advantages expected to accrue later, in point of cost
of production, from the completion of certain cheap
means of communication, and to obtain from the Syn-
dicate the concession of special cheap prices for the coal
purchased from that body in the meantime. In view of
this considerable conflict of interests, it is evident that
a settlement will be difficult, if at all possible, unless the
view that the common interest must override private
claims again becomes predominant.

Coal and Iron Market in Upper Silesia.

The situation has improved, inasmuch as the pits have
been able to increase their output, and thus supply the
demands of the market more fully. Nevertheless, the
latter still preponderate, and stocks are being drawn on
to such an extent that their final exhaustion is
approaching. That increased deliveries could be made
has been due to the endeavours of the railways to cope
with the traffic, notwithstanding military exigencies,
with the result that the difficulties of consumers in the
home country and Austria-Hungary, have considerably
diminished, and the extreme scarcity previously existing-
is no longer apparent. All the different grades of fuel
are in good request, especially gas and coking coals,
which have been scarce all along, and are now still more
so by reason of the fact that the Upper Silesian pits are
called upon to supply districts which formerly purchased
largely from England. The situation of the coke
market is on a par with that of the coal trade, there being
no surplus in any grades, as all stocks have been taken up
along with the current output. The market for
by-products is decidedly firm. The iron ore market is
difficult to characterise, but all the oncoming material
that is at all suitable finds- a ready sale. Holders of
smeltable material are seeking to make the most of the
situation, but this does not alter the fact that the iron
industry in this district has not sufficient material
available to enable it to supply the demand for pig iron.
This is so large that stocks are all gone, and practically
all the deliveries now are new stuff.

Brown Coal Market in Mid-Germany.

The report of the German Brown Coal Association,
Halle, states that the output is increasing, but is not
sufficient to meet the demand by reason of the scarcity
of labour and occasional shortage of railway wagons.
Both overtime and Sunday labour have become
necessary. W ages have been advanced at many of the
mines, and the men are also receiving allowances to
make up for the increased cost of living due to the war.

New Price List of the State Collieries in Upper Silesia.

The following new price list, coming into effect on
April 1, has been issued by the Upper Silesian State
Collieries administration:—Open-burning coals : large,
15’60-15’80 mk.; cubes, 15’60-15’80 mk.; nuts I., 15*60-
15-80 mk.; nuts II., 13*80-13’90 mk.; washed nuts IT.,
13'90-14*50 mk.; peas, 11*50-11*70 mk.; washed peas,
11*50-12 mk.; through-and-through, 13*20 mk.; small,