650

THE COLLIERY GUARDIAN

September 27, 1918.

and showed no prospect of normal conditions. The
proprietors abandoned the exploring work, but were
induced to put down three deep bores on the plateau.
One of these, half a mile in advance of the drifts,
proved 8| ft. of good coal at a depth of 1,080 ft.;
another, about a mile north of this, went down on
basalt; while a third, three-quarters of a mile west
of No. 2, proved 9 ft. of coal unaffected by basalt.
Thus encouraged, work at the drifts was recommenced.
For 5| chains the coal seam was obliterated, then
suddenly a patch of coal—cindered below and clinkered
above—was followed for 2| chains (k, fig. 3), the roof
and floor being basalt. On crossing a small “ roll,”
all appearance of coal disappeared (i, fig. 3). A thin
band of cindered coal occupied the floor between the
rolls, which were now numerous. Above this thin
layer of cindered coal the seam was unrecognisable,
the roof being basalt. Gradually, however, a streak
of cleaF coal appeared under the cindered portion;
this increased, a roll was crossed, and the basalt dis-
appeared from the roof at 69 chains from the com-
mencement. The drift struck thick but very disturbed
coal containing patches of injected basalt, and in
other 5 chains these disturbances disappeared. When
in 8| ft. of excellent coal and 300 ft. under the point

Fig. 3.—Section of Intrusion Faults, &c., at Bulli Colliery.

Scale—Horizontal

of commencement, winning-out operations were begun.
After regrading the drives, endless-rope haulage was
installed, and the old colliery entered upon a new
lease of life.

It is extremely probable that the great width of
this disturbed cindered coal area (75 chains) increases
to the north. When, if it extends so far, it reaches
the latitude of the more northerly collieries, its eastern
fringe will in all probability be found so far inbye
that it is unlikely any attempt will there be made to
prove its width.

Intrusive basalt affects the lower coal seams, so far
as is known, in a similar manner, but probably more
so. At one colliery where the upper coal seam was
normal over a wide area, sinkings to the lower seams
showed these to be intensely burnt and cindered. At
another a still lower seam was found to be utterly
destroyed for a distance of at least half a mile. In
Mount Keira—one of the most southerly collieries—
a considerable area of the thick upper coal has been
transformed into a mass of pentagonal columns of
coal. This, of course, has been caused by the trans-
mission of heat from below. While no exact data
exist, undoubtedly very large areas of the New South
Wales coal seams have been destroyed by comparatively
recent volcanic agencies in the manner described, and
this must militate against future developments in
the rough and difficult country behind the coastal
cliffs.

All the southern collieries have experienced in one
form or another the effects of basalt in their coal
seams. In one case (apart from dykes) an acre or two
of coal may be rendered unmarketable by a layer of
white dolerite on the roof. In another the bottom
coal may in like manner be affected by basalt on the
floor. In one colliery a pear-shaped mass of coal
2| acres in extent, contiguous to an overlap fault, has
been cindered, yet no basalt has been discovered.

“ Horses ” or “ Rolls.”

These strange and perplexing occurrences were
referred to in the writer’s former paper, and he con-
fesses his inability to arrive at a satisfactory explana-
tion of their genesis, but in the hope that some
members may be able to throw some light on their
origin he will describe them in some detail.

Their occurrence is confined to the upper seam and
'the thick coal collieries between Mount Kembla main
adit and the Bulli Collieries, a distance of about ten
miles. To the south of Mount Kembla adit the upper
coal thins off these rolls, which dwindle in height to
a few inches and become a mere ridge on the floor.
To the north of this adit they increase in height, and
seem to bear a relation to the height of the seam.
These “rolls” are much longer than they are broad;
no two have the same height or configuration, and
they seldom rise to the roof of the seam. As a rule,
more or less coal intervenes between their apex or
hump and the roof, which in the case of high rolls
is somewhat tender at that spot. They occur as a
series of ridges that have a north-westerly bearing.
Often they occur so close together that one room or
stall can extract the coal between them, the roll itself
being left as a pillar. In certain zones a greater
width of coal separates them. Where possible, cut-
throughs connecting the bords are placed between or
where the ends of these are lowest. A plan of these
rolls shows that they follow more or less curved lines.

As a rule, they begin in a fine point or ridge of
hard arenaceous black bind that rapidly rises as a
rounded hump-back, and gradually disappears as it
began. Occasionally one has a bifurcated end. In
section and in profile they vary greatly (figs. 4 to 7).
Occasionally shreds or arms of coal are embraced by
projections of shale, and one rounded side of the roll
is generally steeper than the other. Their occurrence
much resembles the arrangement of sand dunes on the
sea coast, but they differ in that the ends are more
tapering.

Some have suggested an aerial origin, whilst others
are convinced they have been formed by mud-laden
currents. Neither of these theories appears to account
for their occurrence or appearance. The intricate
way that projections of coal are occasionally embedded
within them is difficult to understand. In disturbed
situations basalt has issued from the edge of their
“ hump,” so to speak.

To the north of the 90 ft. downthrow in Bulli
Colliery they entirely disappear from the seam; neither
are they found at the Metropolitan Colliery, the
nearest working colliery to Sydney, where the coal
seam averages 12 ft. in thickness. In some of the- older
collieries to the south they occupy a very large pro-

portion of the original coal seam, and wherever found
they sensibly increase the cost of production. In the
situations where they occur they can scarcely be con-
sidered of contemporary age with the coal seam in
which they are found.

“ Faults ” and “ Dykes.”

On the small-scale map of the district (fig. 1) the
approximate position and course of the principal
faults and dykes are delineated, and on the margin
the “ throw ” of the faults and the thickness of the
“dykes” are given. North of the Metropolitan
Colliery, or to the west of the present colliery work-
ings, nothing is so far known regarding these occur-
rences. On the coast line of Illawarra there are many
localities that have been the scene of stupendous vol-
canic activities, where masses of igneous rocks of
various kinds have been ejected or spread as sheets
over carboniferous rocks. At Kiama, Shellharbour,
Port Kembla, Wollongong and its neighbourhood, and
Towagie, near Bellambi Point, masses and sheets of
igneous rock have issued, from which as centres dykes
radiate and intersect the coal field covered by the
adjacent mountain ranges, and often and in a capri-
cious manner destroy large areas of the coal seams.

Bores put down north of Coal Cliff and eastward
of the Metropolitan Colliery have revealed extensive
areas of concealed basalt, the extent and baleful in-
fluence of which one has yet no complete conception.
Intersecting the high plateau and on the rocky
margins of Sydney’s magnificent harbour, numerous
igneous dykes are seen. In the presence of bituminous
strata these dolerites become transformed and lose
their original character and appearance. In this con-
dition they readily weather and dissolve. To their
decomposition and dissemination by rains the rich
soils and the diversified and charming vegetation of
Illawarra is due.

Sydney Harbour Colliery.

The writer referred in his previous paper to two
bores about 2,800 ft. deep that had been sunk on
the shores of Sydney Harbour and had proved the
upper coal seam of the usual thickness, but which
were destroyed by the presence of basalt on the
northern shores of the harbour. London investors
subscribed a large capital to purchase the leases that
had for many years been held, with the object of
sinking the colliery. Prevented by the authorities
from establishing their works on one of the most
beautiful and conspicuous headlands in the harbour,
the company purchased about four acres of freeholds
and water frontage in a densely populated district of
Balmain, and built an extensive retaining wall.
Sinking operations for coal then began.

The site is about four miles up the harbour, and
west of the two bores referred to. No difficulty was
experienced in sinking through the unbedded Hawkes-
bury sandstones and conglomerates, and only an in-
significant quantity of water was tapped in No. 1
shaft. The small quantity of water gave considerable
trouble by depositing a sediment which rapidly choked
the pipes through which it was led. Its effect on
steel or iron was alarming. The 9 in. flanges and
clamps securing 80 lb. steel rails were speedily
attacked and entirely corroded in three years. This
water contained large quantities of ferrous chloride,

and this in presence of air would be converted into
ferric chloride, which at once attacks iron or steel.

When the first shaft was well under way, the
second, 18 ft. in diameter and 150 ft. distant, was
begun. At a depth of about 680 ft. a strong feeder
of water was unexpectedly tapped. This water also
rapidly attacked iron and steel. Fifty-three feet of
cast iron tubbing was put in to dam back the feeder,
but upwards of 300 gallons an hour still found its
way into the shaft. On approaching the coal
measures, considerable blowers of gas were met with.
The main shaft reached a depth of 2,886 ft., but the
coal seam was found to be thin and worthless. It
was divided by a stone band 2 ft. 3 in. thick. The*
upper division of the coal seam was 2J ft. thick, and
the lower only 8 in. The dividing band of stone was
inclined to thicken to the west and to thin to the
landward or eastern side of the long peninsula, on
the eastern margin of which, for some obscure reason,
the shafts had been sunk. The company, however,
had no claim or right to work coal under the land;
it had indeed already been alienated to the surround-
ing owners. Their lease only embraced the coal under
the waters of the harbour. The company had there-
fore to obtain a special Act of Parliament granting
permission to drive a pair of headings under the
properties to the east and to emerge under a bay
of deep indentation of the harbour 1,200 yards distant
from the shafts. When this was obtained, two head-
ings were driven in the coal seam. The dividing
stone band gradually decreased in thickness, the two
divisions of the seam coalesced, and at about 1,20 ,
yards from the shaft a seam 4| ft. thick was found.
The temperature exceeded 100 degs. Fahr., the air
was dry, and much gas was given off. The work of
driving was difficult, and the shale roof began to
“weigh” on the timber. The seam increased to 6 ft.
in one part, but decreased in thickness to the north
and south. A section of the shafts and of this ex-
ploring drive are shown in fig. 8.

It was determined to work the seam by longwall,
with roads every 43 yards, and to conduct the skips
along the faces. For this purpose the headings were
widened and increased in height for safety and for
ventilating purposes, after which they gave no trouble.
The roof consisted mainly of grey arenaceous schist
under very hard sandstone, and came down easily if
brushed at once and kept well up to the coal face,
but if permitted to sag it proved difficult and ex-
pensive to deal with. The quality of the coal was
good, and closely resembled in appearance and struc-
ture South Wales steam coal. It gave off much dust,
but the use of tight skips kept the roads clean. The
seam was easy to work, and the workmen earned high
wages. They showed, however, their usual indifference
by refusing to clean the shale from the floor before
beginning to fill the coal, and this injured its repu-
tation. Their desire to dictate to the management
and the never-ending demands of their paid agitators
finally exhausted the company’s patience, and the
colliery was eventually shut down permanently. If
arrangements could have been made for vessels tq be

Fig. 5.—Plan.

References

■HH coau

Fig. 6.—Side Elevation.

Fig. 7.—Section in New Tunnel, Bulli Colliery.

Figs. 4-7.—Rolls Encountered at Bulli Colliery
always under the staiths, the output would have
increased, but this was impossible. The works were
cramped for space and confined by streets, houses
and the harbour. The whole of the debris from sink-
ing, from making bottoms, and from driving the long
headings—even the ashes from the boilers—had to be
removed by lighters. Coal winding could therefore
only proceed while vessels were under the staiths.
There was no room for the storage of wagons, so that
the position of the colliery on the shores of the harbour
was in reality a disadvantage. These and other dis-
advantages, in addition to the impossible conditions
and the bellicose attitude of labour, forced the closure
of a colliery on which upwards of £300,000 and an
infinite amount of thought and anxiety had been
expended.

Coke Making.

An excellent silvery coke from the bituminous coal
of the Newcastle (New South Wales) district had been
made for upwards of fifty years in beehive coke ovens.
One beehive plant was erected in the southern coal
field in 1891, at which, by crushing the small coal,
a superior hard coke was made. The large smelting
plants at Broken Hill and others formerly imported
the whole of their coke supplies from Germany, the
North of England, or from South Wales. When the
huge deposits of lean copper ores at Mount Lyell
(Tasmania) and others were being developed, proposals
to use Australian coke led to practical experiments