February 28, 1913.

THE COLLIERY GUARDIAN.

451

culminated in the anthracite stage; but the anthracites
are the older coals, the humic and sapropelic coals
intermediate between them.

As a type of estuarine conditions, the great Dismal
Swamp of Carolina is the best analogy between present
and past conditions suitable for forming humic and
sapropelic coals. It is a swamp with free and circulating
waters (in peat-mosses the water is stagnant), the
vegetation sifts the waters, and a pure mass of black
vegetable material is formed, on its way to coal-
formation. Similar swamps, but marine, are the Nipa
and Mangrove swamps of India and Ceylon. Here
material was laid down in situ, and by floods much
drifted matter also accumulated.

The two theories that coal was either laid down in
place or drifted from a distance, once considered
antagonistic, may be said to be both true in different
cases. The purity of coalseams supports the first.
Where coals consist of one type of plant, the first view
is true; where of mixed types, the latter may be, or
both.

Whilst the erect stems of trees in the coal measures
may sometimes indicate deposition in situ, in other cases
it is evidence of drifting, as in the Mississippi snags
to-day. The occurrence *of underclays with Stigmaria
under seams, as a rule, finds its analogy in Mangrove
swamps, where deposition may have been in situ, or
from drifted material. The usual arguments for drifted
accumulation of coal do not hold, but undoubtedly some
coals are due to this, as are the plants in the shales, &c.

Under estuarine conditions there were periods of
elevation and depression, and the plants were both
upland and lowland in habitat. There was gradual
submergence, as shown by silted up plants, and they
survived this some time. Tree forms predominated
during periods of elevation.

Studies of the silting up of lakes, where a sort of
plankton of algae, &c., forms at the bottom, and
vegetable matter accumulates above and along the
margins, suggest that the cannels and bogheads were
laid down in similar conditions. The deposit at the
bottom by the action of bacteria, &c., would become a
uniform opaque structureless mass, as in cannels, &c.
Here drifted material would play a considerable part.

It has been supposed that coal formed slowly, but the
occurrence of coal conglomerates and of washouts
containing coal, as in Warwickshire and Leicestershire,
showed that it was rapidly formed. The metamorphic
origin of coal again is probably not a true explanation
of the facts. Movement, crust creep and pressure may
have helped the biochemical changes and brought coal
to its present state to some extent. The chemical com-
position may be in some measure affected by bacterial
agency. Anthracite, like other coals, owes its peculiari-
ties then largely to the original nature of the accumu-
lation, just as the ordinary humic coals consist of a dull
part containing plant structures, and a bright (dicey)
structureless part, more akin to cannel. The difference
in the resulting ash shows the truth of this explanation.

The flora of the coal-measure period is unique, com-
bining at least seven main groups of plants aud many
species, and huge arborescent forms adapted physio-
logically to the peculiar physical conditions of the
period.

In the first place there were numerous ferns, the
fronds of which are commonly preserved in the shales
and sandstones, and the ironstone nodules. But
though most of these ferns have foliage, like the modern
fern, yet this fructification was in many cases more
advanced, and they were usually homosporous, but
often (Pteridosperms) heterosporous, having micro-
spores and ovules like the higher seed plants. Their
stems also show relationship with a higher type, the
cycads.

Some of the larger fern trunks exhibit the dimensions
and characteristics of tree ferns. Hence there were
probably moisture-loving forms, and others addicted to
high and dry conditions. The phenomenon of hetero-
spory in this group and the other large groups indicates
that in this early period the lines were laid for the
evolution of the higher groups of plants. The small
microspores are the forerunners of pollen grains of the
flowering plants, the larger macrospores, which became
fewer and larger, paved the way for the evolution of
the embryo sac and ovules.

There were also huge forms of horsetail-like plants,
Catamites, now represented by Equisetum. The cones
usually exhibit homospory, but some were heterosporous,
the present-day forms being homosporous, and having
one type of spore. They had stems with secondary
thickening like the higher plants, a device required by
their abnormal height (up to 30 m.). They are common
in the sandstones and shales, and some coals are largely
made up of them. They were evidently lowland plants.

An intermediate group, the sphenophylls with whorls ) they

ORIGIN OF COAL AND THE CARBONIFEROUS
• FLORA*

By A. R. Horwood (Leicester Museum).

At one time the coalfields of Britain were all united,
except along a line running east and west across Central
England, where the barrier intervened between the
North and South Midlands. The Leicestershire coalfield
consists of the Moira district, where the deepest mines
are worked (Church G-resley, &c.), the Central or Ashby
district, unproductive, and the Cole Orton or eastern
district, now extended beneath the red marl eastward
to Desford. The beds are turned up on the north, and
lower measures outcrop at Bretby and north of Lount,
limiting the coalfield to the north. To the west the
coals basset under the new red marl, and are let down
by faults at Netherseal. To the south the beds are
faulted and basset about Heather. A Concealed ridge
north-west by south-east runs from Charnwood under
Market Bosworth, making two shallow basins to the
east and west. On the east the coalfield is bounded by
the Thringstone fault, and just east of Desford older
rocks lie under the red marl. Coal is, next to iron, the
most important economic mineral, our output annually
being over 240 million tons, and our commercial
supremacy largely depends on the maintenance of this
export trade. But only recently Sir William Ramsay
said that our coal supplies would be exhausted in 175
years. During the strike he had suggested the closing
down and firing of mines, and utilisation of the gas
evolved for motive power, &c., in place of coal. Doubt-
less, in the near future, oil, if not electricity, would take
the place of coal for motive power and illumination.
This being so, it is imperative to conserve our supply of
fuel derived from forest lands by reafforesting all avail-
able areas. In Staffordshire even the pit banks are
being clothed with trees. Once all the Midland area
was one vast forest.

The Leicester coalfield has been worked from prehis-
toric times, flint axeheads and wattled workings being
found at Moira and Measham. In 1204 a charter was
granted by King John for working coal at Swannington,
and it was worked onward continuously. In 1832 the
construction of the Leicester and Swannington Railway
by Robert Stephenson marked a period famous in the
annals of railways and mining.

The beds in which coal was laid down were formed
by rivers contributing to a delta system, as shown by
the frequent rock faults (old river courses) in the coal
and sandstone. There are several kinds of coal—
anthracite, humic, sapropelic, brown coal, lignite and peat.

They differ in detail in chemical composition and
physical characteristics; but all possess carbon and
hydrogen, forming the combustible matter, and nitrogen
and oxygen, which are the volatile products or ash.
Sulphur derived from pyrites also occurs, and causes
the explosions in the firegrate. Graphite is the most
perfect form of coal, being pure carbon, but is incom-
bustible. Coals may be classified by their probable
mode of deposition—terrestrial, estuarine and lacustrine.
In peat, brown coal and lignite we have examples of the
first, whilst humic and sapropelic coals may have been
laid down by either of the last means, the latter being
probably lacustrine in origin.

The origin of coal or its history is best studied by
that of the rocks with which it is associated, with the
sandstones, shales, underclays and limestones which are
of aqueous origin and deposited under variable con-
ditions, like coals. Whilst the coal of commerce is mainly
carboniferous in age, it occurs in many other if not
most formations, but humic (house) and sapropelic
(cannel) coals are characteristic of the coal measures.

The mother substance forming coal is essentially
vegetable in origin. The paper coal of Toula is made
up of thin sheets of bark, in which traces of bacteria
occur, showing it owes its present structureless condi-
tion to bio-chemical changes followed probably by
others purely physical. Examined microscopically and
treated with acids, it is made up of woody tissue, some-
times very varied, sometimes uniform. Cannels consist
of algee or spores, and otherwise are structureless. The
perfect impressions in the beds above and below coals
show what originally the seams were made up of. Some
coal balls show the structure of stems as perfectly as
plants to-day.

As peat is forming at the present time in Britain and
Ireland, so, doubtless, coals (such as brown coals and
lignite) were formed in the past. Being immersed in
water, the plants are converted by bacteria, worms, &c.,
into a uniform brown opaque mass. To-day, forest beds
are found to lie between typical peat, as doubtless
originally.

It had been held that all coal began as peat and

* A lecture given to members of the Narborough Literary
Society (illustratedby slides, mapsand specimens).

of wedge-shaped leaves, cones like Catamites, wood like
Psilotum, are also common. Then there were large
arborescent types of lycopods of the club-moss group,
called Lepidodendron, with stems with spirally arranged
leaf-bases, as in Lycopodium. The cones were hetero-
sporous, with microspores above, or on separate cones.
The cone is like the common Lycopodium in form, like
SetagineUa in being heterosporous.

The wood has secondary thickening. Some forms
had seed-like structures, as in th 3 so-called ferns.
Sigillaria was another lycopod with leaf scars in parallel
rows with ribs between, and like the modern soetes.
Both types had root-like organs, Stig maria, common in
the underclays below coalseams.

Another type, Cordaites, was much higher in the scale,
having long strap-like leaves, and male cones of catkin
type. They combined the characters of cycads in the
chambered pith, the maiden-hair tree in the catkin-like
“ flowers.” The leaves and wood resembled that of
conifers.

Here, then, are several groups of highly organised
plants, all combining several general characters, or
synthetic types, which to a great extent hold the secrets
of the evolution of plants throughout past time; hence
their great importance. For between the coal period and
the late mesozoic or jurassic, when Bennettites, another
generalised type leading on to angiosperms, possessing
an embryo sac and a dicotylous embryo, lived, there were
few types which afforded any data upon these questions.

Since the jurassic, again, the key to the origin of
angiosperms has been more or less lost in the records
of the rocks. Hence, then, the importance of the coal
measures from a biological as well as an economic point
of view.

NOTES FRONK SOUTH WALES.

[from OUR OWN CORRESPONDENT.-!

Demand at Cardiff for better Dock Facilities: New
Dock Foreshadowed at the Fort—Probable Revival
of Proposal to Combine Railway and Dock
Companies : Conference of Shippers and Dock
Managers —Port Talbot’s Prosperity and Specially
Favourable Coal Rates—Rating of Collieries—
Swansea Corporation’s Mineral Estate to be
Developed—Many Thousands of Miners to Give
Notice—Some Splendid Dividend Announcements—
Badges for Federationists.

The need for new docks at Cardiff, intensified by
the transport and shipping delays, of which so much
has lately been said, was the subject of special reference
on Saturday at the Tynesiders’ dinner. So many South
Wales business men come from the north-east coast—
“ Tynesider ” has a wide range of meaning at Cardiff—
that this annual gathering brings together a large pro-
portion of the leading business men; all the larger
because, as invited guests, many who are not Tynesiders
also attend. The chairman (Mr. Beckenham, of Furness,
Withy & Co.’s office), said it was a matter of profound
regret that efficient conduct of the gigantic export trade
in coal, even the fullest development of the magnificent
coalfield, should be hampered by lack of shipping facili-
ties. It was a matter that urgently required close
attention, and very active treatment by coalowners,
merchants, and shipowners. Whilst knowing full well
the value of Welsh coal, they must not blind themselves
to the fact that—excellent as it was—there were com-
petitors in the field, and other sources of supply. Any
hindrances to shipments penalised them, and if the
difficulties were not soon realised for local concerns, the
vital question of dock development must soon become
one for a public authority, as in other places.

Mr. D. A. Thomas (Cambrian Combine), also
referred to the matter. He thought the coal trade was
in for a fairly good time, and did not anticipate any
serious labour troubles in the district. Employers and
workmen were both sick of such troubles, and recog-
nised that peace was better than war. The only cloud
of anxiety was that referred to by the chairman. If
demand increased and prices went up, dock and shipping
facilities at Cardiff were not what they ought to be; and
they might be pulled up on that account. Any pressure
of trade now brought dock difficulties, with the incur-
ring of demurrage.

He added the grave statement that one big
company with which he was connected “ had all its
profits eaten up in demurrage.” The coal trade of
Cardiff, though more or less stationary in quantity
during the last three or four years (owing to labour and
other causes) was going to have great developments in
the future; and, unless this question of increased dock
accommodation and facilities was taken in hand soon,
would have endless trouble during the next few