May 4, 1917.

THE COLLIERY GUARDIAN.

853

seams under the water of oceans, rivers, and lakes are
given in the subjoined table: —

Particulars of Coal Seams Worked under the

Waters of Oceans and Rivers.

	Name	Depth	Thick-
No.	Colliery.	of	below the	ness of
	seam.	water.	seam.
New South Wales.		Ft.	Ft.
(1) Australian Agricul-'		r	
tural Co., Sea Pit..		145-190 ..	.15 to 16
(2) Hetton 			300 ..	. 7 to 8
(3) Hetton 			165-300 ..	. 7 to 15
(4) Newcastle Coal Min-	Borehole		
ing Co., A&BPits		145-170 ..	. 6 to 11
(5) Stockton			240-260 ..	7 to 8
(6) Wickham & Bullock			
Island 			.120 260 ..	6 to 16
Cumberland.			
(7) Harrington 		Main Band.	.126-163 ..	.	61
(8) Workington 		—	90 ..	10
Northumberland.			
(9) North Seaton and			
Cambois 		Low Main .	360 ..	. 4 to 6
Durham.			
(10) Ryhope 		Maudlin .	. 1,830 .	. 7
(11) Seaham 		Maudlin	.	1,830 .	5
	Hutton	—	- 4-1
(12) Wearmouth 		Maudlin .	—	. 51
	Hutton	—	. 41
(13) Whitburn 		Maudlin .	.. —	

(1)	Workings extend about' 600 ft. beyond high-water
mark (Pacific). The pillars are 96 ft. by 36ft., the bords
are 18 ft. wide, and the cut-through or cross holings 9 ft.
wide. About 4 ft. of top coal is left next to the roof.

(2)	Workings extend about 500 ft. beyond high-water
mark (Pacific).

(3)	The pillars are made 90 ft. by 24 ft. ; the bords are
18 ft. wide, and the cut-through or cross holings 9 ft. wide
(River Humber).

(4)	The workings extend about 800 ft. beyond high-water
mark (Pacific), including the winnings. About 3 ft. of top
coal is left next to the roof, and a little bottom coal is
also left.

(5)	Workings extend about 2,500 ft. beyond high-water
mark (Pacific). The pillars and bords are of the same
dimensions as those at the Hetton Colliery.

(6)	The pillars and bords are of the same dimensions as
those at the Hetton Colliery (River Humber and Crosby
Creek).

(7)	About 2 ft. top coal and slate is left on, next to roof,
in narrow places. The minimum thickness of cover h's
been fixed at 126 ft. The pillars are left 57 ft. by 52 ft.,
the bords are 14 ft. wide, and the walls or cross holings
are 9 ft. wide. Thus, 32 per cent, of coal is worked, and
the pillars are not crushed. About 66 per cent, of the
overlying strata is compact sandstone. Feeders of water,
occurring in workings where minimum cover had been
reached, have since become quite dry (Irish Sea).

(8)	The workings extend 4,500 ft. under the Irish Sea.
The bords were 15 ft. wide, and the pillars 21 to 24 ft.
thick. The manager, in order to increase the output of
coal, commenced to rob the pillars, this resulting in falls
and feeders of salt water. . Warnings were given as to
what would happen, but these were unheeded. On July £0,
1837, the sea broke in, and 36 men and boys and a number
of horses were drowned, and the colliery irrecoverably
destroyed.

(9)	At Cambois bord-and-pillar longwall is being worked
under the North Sea, and headings are driven 300 ft. in

Fig. 4.—Surface Cracks at Ashland (Pa.).

advance to ascertain the existence of any fault or break
in the strata.

(10)	The workings extend 5,500 ft. from low-water mark
under the North Sea, and over 400 acres of goaf have been
formed.

(11)	The workings in the Maudlin seam extend 5,000 ft.
under the North Sea, and about 85 acres of goaf have
been formed. Twelve pillars, each 120 ft. by 90 ft., have
been removed in this seam under the goaf of the Maudlin
seam, rising seawards from 2 to 2| in. per yard for the last
1,200 ft.

(12)	Workings extend 4,000 ft. under the North Sea.

(13)	Workings extend 4,000 ft. under the North Sea.

Great Britain.—Coal is being worked under the sea
along the coasts of the counties of Northumberland,
Durham, Carmarthenshire, and Flintshire, in England
and Wales, and also to some extent off the coast of
Linlithgowshire, in Scotland. The coal beds dipping
under the Firth of Forth have been mined extensively.
Here there are a number of faults parallel to the shore,
which drop the seams on the seaward side. The bed of
the Firth of Forth, although very deep at places, is
covered first by a stratum of very hard, stiff unstrati-
fied till or boulder clay, which covers the solid rock,
while above this is a deposit of reddish plastic clay,
from 30 to 40 ft. thick, and’in places finely laminated.
This covering forms a waterproof barrier, and prevents
the sea from reaching the underlying strata. There
are four important coal seams, having a total thick-
ness of about 15 ft. The lowest one lies at a depth of
340 ft. at the shaft, and dips rapidly seaward. Opera-
tions of late years have shown that seams can be
worked on the longwall system under the sea, with

faces from 4 to 8 ft. in height, at depths which are
small in comparison with those of the workings in most
modern collieries. The seams have been worked in
three instances to their outcrop against the boulder
clay, at depths from 137 to 400 ft. below high-water
mark, without any accident. The thickness of the
cover under which the whole of the coal seam has been
mined is less in this mine than in any other submarine
mine in Great Britain.

The workings extending farthest seaward are those at
Whitehaven, which at the William pit extend under
the Irish Sea a distance of 19,000 ft. (1901) from high-
water mark. The coal seam is 10 ft. thick, and is
worked by rooms 18 ft. wide, with pillars 75 ft. square.
There is also a higher seam about 7 ft. thick, which
has been worked in places. North of the William pit
is an old mine which has been flooded.

The mining of undersea coal will become a very
important matter in time in Scotland.

Restrictions have been imposed upon the working of
Crown coal in Great Britain. In the case of one
colliery, the working of coal under the ocean, unless
there is at least 126 ft. of strata between the bed of
the sea and the top of the seam, and the removal of
pillars or the adoption of the longwall system, where

Fig. 5.—Cave in Soft Soil.

there is less than 360 ft. of intervening strata, are
prohibited. Under specified conditions, the entire
removal of the coal seam is permitted where the mini-
mum thickness of cover is 270 ft.

It has been advised that the workings of coal on the
Northumberland coast be limited to areas where there
is a minimum of 270 ft. of solid strata above the seam.
The bed of the ocean generally consists in this vicinity
of a stiff clay.

Australia.—In New South Wales, coal mining has
been carried on extensively beneath the River Hunter,
the Pacific Ocean, and its tidal waters. Four seams
have been worked in parts of this area, the total
thickness ranging from 19 to 43 ft. Operations in the
vicinity of the outcrop are dangerous, because channels
in the coal measures become eroded by old streams, and
later these channels become filled with alluvial
deposits. In general, the coal measures dip slightly
towards the ocean, but there are many local dips and
faults. The usual dip is given as 1 in 36. There are
thick deposits of clay covering the outcrops in places.

Owing to the weakness of the roof, a number of inun-
dations have resulted at inshore mines from letting
down the sand overburden. In consequence of a fall
of roof, there was a rush of water into the Ferndale
Colliery in 1886, and a miner lost his life. A Com-
mission was appointed to investigate this accident,
and the report submitted included a review of condi-
tions at all the collieries in the district. The title to
the coal beneath the River Hunter and the tidal waters
resides in the Crown, and the leases to these coal lands
now include regulations controlling the method of
mining beneath bodies of water, with the view of pro-
tecting life, and also of preventing large volumes of
water entering old workings, and thereby interfering
with the mining of the coal in the adjacent area.

The mines of the district use the pillar-and-room
system. The dimensions of pillars and rooms vary,
but, in general, 50 per cent, of the coal is recovered.
The practice in a number of the mines is to drive
18 ft. rooms, leave 24 ft. pillars, and recover part of
the pillar coal. When the pillars were left only 18 ft.
wide on first mining, a number of crushes resulted.
Owing to the presence of thick, impervious beds of
clay, no water entered the mines where these crushes
occurred, although at equal depths on land the crushes
caused surface subsidence and some damage to build-
ings. In one of the mines the rooms are 18 ft. and
the pillars 36 ft.

The quantity of water being pumped from the mines
varies from 50 to 600 gals, per minute, and in most
places this water is decidedly salty. Vertical bore-
holes are put up to determine the thickness and char-
acter of the overlying beds.

In determining the safe working limit under the
ocean, the following conditions have been considered:
The character of the overlying strata, with special
reference to loose deposits of alluvium or beds of clay
between the bed of the ocean and the coal seam ; the
presence of faults and dykes in the strata; the dimen-
sions of pillars to be left, and the width of openings
to be made; the utility of leaving coal next to the
roof in some cases.

The special conditions of working under tidal waters
prescribed in the leases are notably as follow: —The
maximum width of rooms shall be 18 ft., and the mini-

mum width of pillars 18 ft.; the pillars 18 ft. wide
shall not be removed; all headings and rooms shall be
driven on sights; all workings shall be surveyed
accurately every three months (all dates of working
must be shown on the plan); the plan of the mine
shall contain a faithful record of all dykes, fissures,
etc., and shall indicate all excavations as they actu-
ally exist; in one road of every pair of leading head-
ings a borehole shall be kept going 10 ft. in advance,
and all leading headings shall be driven at least 150 ft.
in advance of the working rooms; when dykes or
fissures are stuck in the boreholes, precautions must
be taken to protect against possible danger which may
result from weakness of roof or flow of water when the
dykes or fissures are penetrated by the heading; the
coal under the ocean should not be attacked until after
a large goaf has been made by extensive workings
under the mainland; the most accurate information
available shall be obtained as to thickness and char-
acter of the strata and estuarine deposits overlying
the coal seam before commencing to work it.

Similar conditions are specified for working under
the sea, except as follow:—The minimum width of
pillar shall be 24 ft.; all leading headings shall be
driven at least 300 ft. in advance of the working
rooms; boreholes penetrating
the roof for a height of 30 ft.
above the coal seam shall be
driven on the leading head-
ings 300 ft. in advance of the
work, and 60 ft. apart.

Newfoundland.—At Wabana
there is a series of iron ore
beds which lie in a synclinal
trough, one edge of which
passes through Belle Isle. The
three uppermost beds are
mined in both the land and in
the submarine areas. The ore
beds pass beneath -Conception
Bay, and apparently outcrop
in the floor of the bay. The
centre of the basin is esti-
mated to be about three miles
from shore. The lowest bed
is from 15 to 30 ft. thick. The
method of mining is pillar-
and-room, the rooms being
250 ft. long, and turned on
35 ft. centres, with 20 ft.
pillars.

The development in the
submarine territory is suffi-
cient to allow an annual
output of one million tons,
and the total ore reserve
has been estimated at practically 400 million
tons, after proper allowance was made for pillars,
faults, and poor zones. The principal dre bed
outcrops on Belle Isle, and dips seaward, so that at
high-water mark it has a depth of 70 ft.; at 3,000 ft.
from shore the bed is 268 ft. deep, and has 180 ft. of
cover. The average grade of the slope is 16 per cent.
According to the geologist to the Tennessee Coal, Iron
and Railroad Company, the longest slope at the
Wabana mines in 1913 was 7,500 ft., and the end was
6,000 ft. under the water.

Cape Breton Island. — The coal measures of Cape
Breton Island extend under the ocean, and a number
of the coal seams have been worked in these sub-
marine areas. The measures dip at a steep angle,
while the sea floor dips at a moderate angle, so that
the thickness of cover increases rapidly. Owing to
the rapid erosion of the outcrop by the sea, some of
the seams have been lost. The Mabou mine was flooded
from the ocean because of a break in the roof in 1909,
and the Port Hood Colliery was lost by a flood result-
ing from the entrance of water through a feeder which
was opened when pillars were extracted at a point
where 942 ft. of solid strata were supposed to lie
between the coal seam and the floor of the ocean.

The workings of some of the companies have already
been extended seaward a distance of 2J miles from
high-water mark, and it is probable that in the future
a large part of the coal output will be obtained from
these submarine fields. The Government has pre-
scribed regulations to control the size of openings and
methods of working under shallow cover. Where the
cover is less than 180ft., the coal may not be mined;
mine openings may be driven where there is not less
than 100 ft. of cover. Where there is less than 500 ft.
of solid cover, the workings must be divided into sec-
tions not more than half a mile square, and a coal
barrier not less than 90 ft. thick must be left around
each section. The barrier may be pierced by not more
than four openings, not more than 9 ft. wide by 6 ft.
high. In 1904 the Government mine inspectors and
the management of the Dominion Coal Company
agreed upon the size of pillars to be left in the mining
of submarine coal. With rooms 20 ft. wide, the size
of pillars left in the Harbour seam increases from
27 by 75 ft., at a depth of 200 ft., to 72 by 75 ft. at
1,000 ft.; and in the Hub and Phalen seams from 30
by 75 ft. to 90 by 75 ft., the respective percentages of
coal left being 51 and 70.

British Columbia.—-A disaster which may be com-
pared with those occurring in subaqueous mining
resulted when the workings of the old Southfield
Colliery, near Nanaimo, British Columbia, tapped the
drowned workings of the South Wellington Mine No. 1
of the Pacific Coast Coal Company on February 9, 1915.
The inrush of water resulted in the death of 20 men.
It was believed that the new workings were 450 ft.
away from the water, and it was planned that a 100 ft.
pillar should be left between the water and the new
workings.

Japan.—A large proportion of coal is mined under
the ocean in Japan. The most serious accident in the
whole history of subaqueous mining occurred in that
country on April 12, 1915, when 237 men were killed
by the flooding of Higashimisome Colliery. The mine
is situated in Ube, Yamaguchi-ken, and the chief pro-