THE W.A. NATURAL HISTORY SOCIETY.
At the usual monthly meeting of the West Australian Natural History
Society, held yesterday evening, at the offices of the Government
Geological Department, Beaufort-street, Mr. B. H. Woodward read an
interesting paper on coal and lignite. There was a good attendance of the
members of the Society, and the Vice-president (the Hon. J. G. H. Amherst)
presided.
Mr. BERNARD WOODWARD said:
The consideration of coal may be taken up from various points of view, both scientific and practical, but this evening we are chiefly interested in the former, and will endeavour to review what geology, mineralogy, palaeontology and chemistry can teach us on the subject. The name coal, spelt cole, until a comparatively recent period, is derived from the root col, or kull, meaning fuel, and is common, to all the languages comprised in the Teutonic group of the Indo European family of languages.
GEOLOGY.
As a matter of custom the term coal is applied to almost every kind of
solid mineral fuel, but by geologists it is used specially to designate
those mineralized plant remains that occur in the upper series of the
Palaeozoic rocks known as the carboniferous system, because seams of coal
form one of its distinguishing characteristics in most parts of the world.
Seams of coal also occur in the Old Red Sandstones, the Permian and the
Triassic series. While to those coals found in Mesozoic rocks the term
lignite or brown coal is applied. These occur in both the Jurssic [sic]
and the Cretaceous epochs, but more notably in the latter, in which seams
over six feet in thickness are worked in Germany.
The New Zealand and Californian coals are of this age.The brown coals of Germany are chiefly of Tertiary age (Oligocene). In Greenland the latest Arctic Expedition discovered a bed of coal of Miocene which so recently although it is as black and lustrous as the Palaeozoic fuels.
The peat that is still in process of formation in the bogs of Ireland, may be described as a poor kind of coal that only requires subjecting to heavy pressure to produce a fuel equal in value to many of the lignites, an event that may occur by ordinary natural causes in the course of time. Thus we see that nature has provided us with a vast number of beds of fuel extending from the Devonian Age up to the present time; and these vary in strucure [sic] and appearance from the peat and the soft and earthy peat coals the paper coals occurring in thin yellow grey layers like compressed leaves of paper, to those lignites having a distinctly woody appearance, and hence termed “wood” or “board coal,” and to others as hard and black as true coal and known as “stone” coal, so that it is impossible to tell by simple inspection whether some of these hard black fuels be true coal or merely superior lignite, some of the latter being far superior as fuels to many of the poorer coals.
Consequently difficulties arise as to the exact definition of coal, the engineer, the manufacturer, the merchant, being only interested in these fuels as far as their economic value is concerned, whilst the geologist classifies them according to their derivation, which led to some curious evidence being brought forward in the remarkable case which was tried in 1853, at Edinburgh, before the Lord Chief Justice and a special jury to settle the question, What it] coal?
The owner of an estate had granted a lease of the whole coal contained in it. In the course of working, the lessees extracted a combustible mineral of great value as a source of coal-gas, and they realized a large profit by the sale of it as gas-coal. The lessor then denied that the mineral in question was coal, and disputed the right of the lessees to work it. At the trial there was a great array of scientific men, including chemists, botanists, geologists, and microscopists ; and of practical gas engineers, coal viewers and others there were not a few. On the one side it was maintained that the mineral was coal, and on the other that it was a bituminous schist.
The evidence, as might be supposed, was most conflicting. The judge, accordingly, ignored the scientific evidence altogether, and summed up as follows ;—“The question for you to consider is not one of motives, but what is the mineral ? Is it coal in the language of th[ose] persons who deal and treat with that matter, and in the ordinary language of Scotland ? Because, to find a scientific definition of coal after what has been brought to light within the last five days, is out of the question. But is it coal in the common use of that word as it must be understood to be used in language that does not profess to be the purest science, but in the ordinary aceptation [sic] of business transactions reduced to writing ? Is it coal in that sense ? That is the question for you to solve.”
The jury found that it was coal. Since this trial the mineral has been pronounced not to be coal by the authorities of Russia, who accordingly have directed it not to be entered by the Custom-house officers as coal.
PALAEONTOLOGY.
As we have before said the geologist calls that true coal which is of carboniferous age, and to determine this point he has to call in the aid of the palaeontologist because the age of rocks is determined by the fossil remains of plants and animals found in them; for a certain order of appearance characterises these organic remains, each great group of rocks is marked by its own special types of life, and these types can be recognised, and the rocks in which they occur can be correllated, even in distant countries, where no other means of comparison is available.
In the Devonian system, only algae and other cryptogams with a few cycads and conifers are found. In the Carboniferous ferns attained a special development, as did certain lycopodiaceae, known as sigillaria and lepidodendra, these reaching 60 to 100 feet in height, with a diameter of 40 inches, while their modem representatives the club-mosses rarely exceed 8 or 10 inches in height. Gigantic equisetaceae known as calamites were equally luxuriant. True coal consists of the remains of these plants.
In the Permian system palms first appear. In the Secondary or Mesozoic age, the forms characteristic of the palaeozoic beds, sigillarae, lepidodendra and asterophyllites (ferns) disappear; and in the Jurassic times the prevalent forms in the forests were cycads, and with these were associated numerous conifers related in form to our arancarias and thujas, with an undergrowth of ferns and fleshy fungi.
In the later Oolitic times the earlier forms of cycads and ferns disappear, and are replaced by those more nearly related to those of the present time.
In the Cretaceous system the dicotyledonous trees appear, being represented by juglandites and ac[c]rites, related to our walnuts and maples, also alders and hornbeams and shrubs allied to our willows, while the cycads are much diminished in numbers.
In the Kainozoic or Tertiary strata the flora approaches still more closely to the present, for the brown coals of Germany of this age are composed almost entirely of the remains of conifers, although oaks, beeches, birches, alders and willows have assisted in the composition.
Peat, the formation of which is now going on, is composed chiefly of bog-mos [sic], Sphagnum palustre, which has the curious property of growing on upwards while the stem decays. Many of the plants have been beautifully preserved in the shales associated with the various coal measures, its can be seen in the collections exhibited in our Geological Museum, while microscopic sections still further help to elucidate the mystery of the composition of the coals, for even when they have been so much altered that the stems and leaves are represented by nothing but a structureless mass of black carbonaceous matter, there are found diffused through this a multitude of minute resinoid yellowish brown granules, which represent the spores of the gigantic Lycopodiaceae of the carboniferous flora. The of course do not occur in the lignites, which generally show a true woody structure under the microscope.
Although for want of time I have only referred to the flora, Yet in the identification of strata the fanna [sic] is still more important, because more numerous, and I would call the attention of members to the collection of the British carboniferous fossils in the Geological Museum, and ask them to compare them with those from the Irwin district, when they will be speedily convinced that that is truly of Carboniferous age.
MINERALOGY.
Considered from a mineralogical point of view, coal is placed in the hydro-
carbon group, along with petroleum, the wax-like parrafin series, amber,
the mineral resins, asphalt, &c., all of which are believed to be of
organic origin, although so much altered as to have lost all trace of
organic structure, as is the case with albertite—a brilliant jet black
hydro-carbon found in the lower Carboniferous rocks of Nova Scotia—which
is very valuable for gas-making, but only occurring in irregular fissures
cannot be regarded as a coal. The chief varieties ties of coal
are—firstly, anthracite, which contains 80 to 95 per cent. of carbon, but
graduates into the next variety, bituminous coal, which contains from 73
to 90 per cent. of carbon, and is divided into caking and non-caking, the
latter approaching most nearly to anthracite in composition, and being
also termed free-burning or steam coal, according to the purposes for
which it is used ; secondly we have cannel coal, the name being corrupted
from candle, because a because a splinter can be lighted and will burn
with a flame. It differs very little in composition from some of the
bituminous coals, but yields on destructive distillation large quantities
of gas and oils, both burning and lubricating ; and lastly, there is
torbanite, an earthy variety of cannel that yields large quantities of gas
and oil, but leaves an ash almost at bulky as itself. This was the subject
of the 1853 law-suit above mentioned. Then come the lignites or brown
coal, of which jet is a variety.
CHEMISTRY.
In the next place we will see what light chemistry can throw upon our
subject. Coals may be analysed to show actual per centages of carbon,
hydrogen, oxygen (these two apart from the amount contained in the water
which would have been previously been driven off), nitrogen, sulphur, and
ash, and the ash may be separately analysed, as is done to ascertain if it
contain anything that will interfere in metallurgical operations. Analyses
do not always throw much light upon the economic value and uses of a coal,
for a good deal depends upon the way in which the molecules arranged, for,
as before mentioned, some bituminous coals yield much more oil than others
of almost identical chemical composition, their constitution being
evidently widely different. In Lignites the amount of carbon varies from
49 to 75 per cent., hydrogen from 3.79 to 5.63, nitrogen from 0.57 to1.34,
sulphur from 0.49 to 4.59, ash from 1.83 to 19.34, water from 5.90 to
49.50, the specific gravity from 1.13 to 1.41. In coals the carbon varies
from 70 to 95 per cent., hydrogen 4.65 to 6.00, nitrogen 1.49 to 2.65,
sulphur 0.55 to 1.51, ash 0.79 to 4, water 1.35 to 3.50, and the specific
gravity from 1.25 to1.46. From these figures we see that coals [sic]
contains more carbon and hydrogen and less nitrogen than lignite, but the
latter contains much more water and generally more ash. The assay method
of estimating fuels is of more practical value, giving the amount of
water, ash, coke, and volatile hydro-carbons. Coals give from 50 to 90 per
cent. of coke, and from 8 to 33 per cent. of gas, except in the case of
some of the superior cannel coals which give up to 66 per cent. of
volatile matter. Lignites give from 30 to 63 per cent. of coke from 15 to
36 per cent. Gas.
CONCLUSIONS.
To sum up, it is impossible to distinguish coal from lignite by external
appearance, or by chemical analysis the superior lignites being better
fuels than some of the inferior coals. The lignites mostly contain much
more water than coal, and while the latter may be dried it is useless to
perform that operation on lignites for they re-absorb water from the
atmosphere almost to the extent of that driven off. While only some coals
are non-caking, all lignites are and so nearly valueless for gas-making as
the coke being left in powder has no commercial value. Lignites are often
valuable fuels, and are largely used in all parts of the world. In this
colony there are many beds of lignite in the southern districts, some of
which like the Flybrook and Fitzgerald are so friable that they are never
likely to be of much commercial value, but the Collie will be most useful
for household purposes, locomotives, smelting works, &c., though it cannot
be economically employed in gas making, as it does not cake, and so does
not give coke of any value, nor will it not be accepted by mail steamers
on account of the large amount of water it contains, necessitating the
carrying not only of the additional ten per cent. of useless water but
enough extra fuel to drive that off. It is hard and travels well, and so
will certainly be a source of great profit. Our great hope, however, of
finding good steam and gas coal lies in the districts extending from the
Irwin to Kimberley, where the Carboniferous formation is so largely
developed as stated in the reports of the Government Geologist.
The GOVERNMENT GEOLOGIST (Mr. Harry Page Woodward) gave an interesting description of the different formations of coal in this colony. The collie coal resembled very closely lignites, and he put it down as Mesozoic coal. certainly not the coal of the Carboniferous Age, and as it was generally decided that anything that would sell in the market was coal he had called it coal.
There were very large seams there, and extended a great depth. The coal was a coal that would travel. But at present the colony had no great need for coal, as, if the coastal steamers used it, and the railways used it, the total amount they would require would not keep one mine going. As far as the prospects for coal in this colony were concerned, he considered the colony had very fine prospects indeed, for the Carboniferous rocks outcropped in many places between the Irwin and Wyndham, in fact they were more largely developed than in any other part of the world.
Mr. R. WYNNE said that about a year and a half ago a gentleman visited this colony who was an expert in coal, and he took the opportunity of showing this visitor a specimen of the coal from Fly Brook. The gentleman in question immediately pronounced it to be lignite and that it was of similar quality as the lignite used at the present time throughout New Zealand. It was, he said, bound to be very valuable for fuel. It was of much more recent formation than the other coal, and possibly the other coal might be found underneath at a greater distance.
The GOVERNMENT GEOLOGIST said that it was very often thought by the public on seeing lignite that it was an indication of coal. This was a mistake as lignite had nothing to do with coal, as the lignite rested on very old crystaline rocks, rocks of an age beyond the Palaeozoic rocks.
Dr. JAMESON proposed a vote of thanks to Mr. Woodward for his interesting paper. He thought the question he had gone into was one full of interestat the present time. He had shown them the great complexity of the subject and the difficulty of forming a true opinion. Perhaps it would be better to leave the matter to thoroughly scientific men, and not to experts. It seemed a strange thing that they should apply, as on a recent occasion, to a gentleman from the other colonies for an opinion on the coal, when they had men of a scientific education here.
Mr. POOLE seconded the motion which was carried unanimously.
Mr. WOODWARD said he had had some conversation with Mr. Bond with regard to the Irwin coal, who told him he was going to continue boring and prospecting in spite of any adverse report.
The business of the evening was conc[luded] by the notice that at the next meeting [the] Government Geologist would give a pap[er on] gold....
