February 11, 1916.

THE COLLIERY GUARDIAN.

265

and Penshurst borings were made. The problem is
still more intricate since the discovery of the extent of
the coal field as far northwards as Ramsgate. The
writer believes it is possible to remove the difficulty, for
he has made a careful study of all the borings and work-
ings for coal in North-Western France, and he intends
publishing a paper on this question. As a summary of
the results of this study, the writer may quote the
following data :—The nonth-west -extremity of the Pas-de-
Calais coal field is on or near the apex of a transversal
fold, which separates the Continental from the British
coal measures. East of this axis the general pitch- of
the basin is eastwards, while on the west it is west-
wards. By a series of folds, on echelon, the coal
measures west of this fold make for the north-west, up
to the outcrops of the Boulonnais. Numerous trial
borings have been put down west of these outcrops in
search of the Dover coal measures. From these results
one may grasp that the same structure, en echelon, is
found; two folds rolling in amidst Silurian rocks,
devonians, carboniferous limestones, and coal measures.
The northernmost fold has been proved by the borings
of Calais, Marek, and Ofiekerque, which found upper
devonians and lower carboniferous rocks sometimes hori-
zontal. This is, the writer thinks, the true prolongation
south-eastwards of the Kent coal field in the older rocks.
The axis of the Kent syncline, as drawn by Arber, pro-
longed south-eastwards, falls in this Calais syncline.
According to the intensity of denudation, the coal
measures may or may not stretch from the northern
syncline to the coal measures of Strouanne, in the inter-
mediate syncline, and from this one to the Boulonnais
coal field.

The Big Overthrust Fault. — All along the South
Wales-Namur syncline this fault plays an important part
in the structure of its southern margin. Along the plane
of this, and of the associated faults, extraordinary dis-
turbances took place, and a most complicated structure
originated. Tracing the course of this fault in a coal
field of this syncline is, therefore, of paramount import-
ance, as much from the industrial as from the geological
standpoint. From the Mendips to the Boulonnais coal
field we have not the slightest clue as to its existence,
although every probability points to its continuity,
especially in Kent, not far from the Boulonnais, where
the overthrust of the faults is more in evidence than
elsewhere; ■ nearly the whole coal field is still buried
under thrusted carboniferous and devonian formations.
We have, therefore, to rely entirely on theoretical
speculations to trace the fault, and the writer will pro-
ceed, by way of comparison, from the known to the
unknown. If a north to south line be drawn from the
Forest of Dean to the Mendips, three synclines are found
along this line, whose structures are different. Starting
from the big overthrust fault running along the northern
slope of the Mendips, the writer finds : (1) The Radstock
portion of the Bristol coal field, which is absolutely of
Belgian type, as pointed out long ago, with thrust and
slide faults, and overfolded and sharply plicated beds.
It may be said at once that hitherto there is nothing in
the Kent coal field to remind us of such a structure. (2)
The northern portion of the Bristol coal field, separated
from the foregoing by an overthrusted east and west
anticline, is much more regular, but still disturbed by
normal faults, and displaying rather steep dips. In both
these synclines the sequence from the lower carboni-
ferous up to the upper coal measures is continuous or
nearly so. (3) The Forest of Dean coal field : Regard-
less of the Malvernian' disturbances on its eastern
margin, this syncline is much more regular, and its
more perfect basin-like structure is known. The upper
coal measures of this coal field rest conformably on the
lower carboniferous. By comparing the characters of
the Kent -coal field on the one hand, and of these three
synclines on the other, the writer is inclined to believe
that the position of the Kent basin transported on the
above line should be mid-way between the Forest of
Dean and the Bristol coal fields, where formerly, before
the denudations, middle coal measures doubtless rested
unconformably on the lower carboniferous, as they do in
Kent, and where the structure was no less regular. The
strata of the Kent basin seems to have undergone little
disturbance, for no trace of faulting has been recorded
in the borings except at Mattice Hill, and still the
borings are in such a number that faults of importance
would hardly have escaped detection in one or more
boreholes. Even in the southernmost part of the known
coal field area, in the Dover Colliery, the rocks are
nearly horizontal, this affording no clue of the approach
of the fault. The big fault reaches the French shore
of the Straits at Cape Grisnez, with a west-north-west
. trend. It seems very difficult to trace the fault from
Grisnez to the east of Brabourne, as M. L. Breton did,
for this would need a sharp bend of fault. If no change
takes place in the trend of the fault, in the Straits, the
fault must run much further southwards, leaving room,
south of Dover, for another coal field displaying the two
kinds of structure of the Bristol coal field. This hypo-
thetical coal field may or may not be separated from the
Kent coal field (like the Forest of Dean) by a ridge of
older rocks. Against this hypothesis, the writer may
quote the fact that the Kent coal is reported to be brittle
and crumbling, like the Belgian coal, no doubt under
the influence of the disturbance.

The Concealed Coal Field of Southern England.

In 1901 Dr. Strahan pointed out that, regardless of
the Kent area, no fresh light had been thrown on the
problem of the existence of coal in Southern England.
The same may be said to-day. Some borings since 1905
proved the palaeozoic floor in the London area, but the
problem is still very obscure. In 1902 the writer
attempted to sketcli the structure of the London
area assuming the structure to be comparable with
the structure of the Hercynian folds in Northern
France, and supposing the red rocks of the south
of London borings to belong to the lower old red

sandstone. The old red sandstone age of these rocks is
no more questioned to-day, but since the boring at
Southall it seems probable or possible that they are of
upper old red sandstone age. As it is well known, the
old red sandstone which borders the coal fields of South-
West England has many resemblances and differences
with the devonian rocks of the Continent, the most strik-
ing difference being the existence, on the Continent,
of a marine middle devonian division. The indubitable
existence of marine middle devonian in two London
borings, shows the London area to be connected with the
Continental devonian. Through the courtesy of Dr. A.
Strahan, the writer had the opportunity of studying the
red rocks from the Streatham and Grosness borings, and
he has some personal experience of these red rocks, for
he mapped an extensive tract of them for the Geological
Survey of Belgium. Moreover, in the last few years he
has split very many cores of boreholes through the
same rocks. From their lithological characters, he has
no doubt that the 8treatham and Grosness red rocks
are lower old red sandstone, for they are unlike any
upper old red sandstone that he has seen. But after-
wards, he had the opportunity of studying the red rocks
from the Southall boring through the courtesy of Prof.
W. Watts and E. Proctor, in the collection of the Royal
College of Science, and also through the courtesy of Dr.

A.	S. Woodward, he saw the same rocks and their
fossils in the Museum of Natural History. Dr.
Woodward, who determined the fishes from this boring,
pointed out that they are beyond any doubt upper old
red sandstone fishes, and still these Southall rocks from
their lithological characters are of lower old red sand-
stone type. We have, therefore, no means to settle the
problem of the age of the red rocks of the London area
on lithological grounds. Moreover, according to the last
map of the London borings, these red rocks surround the
two borings where marine middle devonian fossils have
been found. At any rate, this structure is different from
the structure observed in the immediate neighbourhood
of any French or Belgian coal field. Therefore, should
any coal be in the London area, it ought to be much
further southwards, a conclusion already arrived at by

B.	Dawkins. The true lower old red sandstones (lower
devonian) and the big fault which runs along their
northern margin should be, therefore, also much further
southwards, a conclusion agreeing with the above study
of the Kent coal field.

As‘the writer has already stated, there is some pro-
bability of the existence of another coal field west of
the main Pennine anticline. Many years ago Ed. Hull
put forth an ingenious idea. He had shown that the
carboniferous rocks owe their basin-shaped structure to
the intersections of the two north-to-south and east-to-
west systems of post-carboniferous flexures. Applying
this observation to the study of the concealed coal field
of South England, he stated that the position of the
supposed coal fields, lying between these flexures., may
be predicated by the knowledge of the southwards pro-
longation of the transversal anticlines of the Midlands
and of the position of their intersection with the main
anticline. Now that the writer has attempted to trace
these Midland anticlines southwards, he will deal with
the intervening syncline, about which he may state the
following considerations :—

(1)	No transversal anticline is known in the South
Midlands, between the Malverns and Gharnwood Forest,
except the unimportant Lickey Hills and Dost Hill.
Therefore the southern syncline does not display
important transversal divisions.

(2)	As the Woolhope anticline is seen crossing the
Malvernian range, it is likely to stretch to the Mendip
anticline, and to break the south-west corner of the
syncline.

(3)	There is some possibility of the syncline being cut
diagonally by a hypothetical north-east to south-west
Caledonian ridge. The north-eastwards prolongation of
some Cornish anticline, and staked out by the. under-
ground palaeozoic platform, is not to be mistaken from
the tectonic ridges, as pointed out rightly by A. Strahan.
But in this case, he says, the age of the rocks of this
ridge is highly significant of an old line of upheaval,
inasmuch as this ridge was the south-east shore of the
triassic sea of Central England.

(4)	If the dissymmetrical profile of the Pennine chain
holds good at its southern end, then the syncline west of
the chain must be deeper than the syncline east of it
(the Kent syncline), and in this syncline the deepest
part must be at its south-east corner, and therefore south
of the above diagonal ridge.

(5)	There is some actual evidence of the existence of
coal measures in this syncline on the results of the
Batsford and Burford borings. From the section of
these borings there is some reason to believe that upper
measures were struck, which is in accordance with the
fact that these borings are not far from the crest of the
Wales-Brabant anticline, and also with the overlap
observed along the parallel line of the Malvernian range.
The existence of the supposed upper measures not far
from the southern limit of the upper measures of the Mid-
land syncline, is another evidence that a large part of
the Wales-Brabant anticline was submerged in England
during the upper coal measures period. Another tract of
these upper measures may have extended along the
eastern slope of the Pennine chain, between Kent and
Yorkshire, but as this coal field was more shallow, and
this part of England was during long periods an elevated
country, these measures have doubtless been denuded.

The writer does not intend to describe other coal fields,
for a volume would be necessary for such a purpose.
Enough has been said, he thinks, to prove the com-
plexity of the problem of drawing the relationships
between the detached coal fields and their extent. The
hypothetical character of most of his conclusions will
prove, beyond any doubt, how far we are still from a
perfect settlement of this problem, and how much this
settlement is dependent on the state of minute know-
ledge regarding all the geological features of these coal
fields, and of the surrounding country.

COKE, ANTHRACITE SLIME, AND
ANTHRACITE DUFF AS BOILER FUEL.

By E. Gevers-Orban.

The Colliery Guardian of January 21 gave a drawing
of a new German coke burning furnace, in which the
fuel is ignited before entering the furnace proper. The
personal experience of the writer is that the ignition of
the coke on an external grate, in the bottom of the
hopper, is somewhat difficult to regulate, and that the
refractory lining of that part of the furnace is specially
liable to deterioration.

At a Belgian colliery these difficulties have been
recently and successfully overcome in another way.

The mechanical grate A is of the long hollow step
type, with a reciprocating action; and the coal is pushed
from the hopper bottom into the furnace by means of a
piston B. The ignition process described below could
probably, however, be adapted to many other mechanical
grates.

The whole question is, indeed, how to obtain per-
manently at the discharge end of the hopper, that is, at
the front end of the grate, a sufficiently high tempera-
ture to ignite the non-gaseous fuel, such as coke or
anthracite.

In our case, a low refractory vault C, above the grate,
forces the burning gases to proceed upwards, close
along the grate, and thus brings them in close contact,
in a burning condition, with the coal entering the fur-
nace. In this way, coke dust ignites easily and regu-
larly, as do also anthracite dufi and slimes from the
anthracite coal washer. Special mention may be made
(as a usual fuel) of wet anthracite slime with 30 per
cent, ashes and 18 per cent, water, which burns regu-
larly, without addition of any other coal, and raises an
ample supply of steam for the electrical plant of the
colliery. Each pound of this anthracite slime raises, on
the average, 3 lb. of steam at 1201b. pressure.

In similar furnaces the following points should be
carefully considered :—

(1)	Firebricks.—The temperature below the main
vault is very high, say, 1,200degs. Cent., and is neces-
sary to keep the fire burning regularly. Hence the
vaults and refractory linings, which are exposed to great
strain and wear, should be designed with care and skill.
At first they were a cause of much trouble.

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(2)	Preventing Clinker.—Owing also to the high
temperature, the ash is very liable to clinker and adhere
to the grates. In the furnaces referred to, owing to the
good refractory quality of the ashes, no such incon-
venience has appeared; but if clinker were to form, this
could be prevented by«mixing the indrawn air with
steam or hot fuel gases.

(3)	Dust.—The burning of gasless slack requires a
strong forced draught, which means that a quantity of
half-burned dust is carried along with the burning gases,
and deposited everywhere in the flues. These latter
should be specially designed to admit of easy and
frequent removal of such dust. With wet anthracite
slime, the amount of this dust is about 5 per cent, of the
fuel consumed. With dry anthracite dufi, the writer
has not had any large personal experience, but the igni-
tion is easier in the dry state than in the wet condition.
The quantity of dust carried ofi in the gas would pro-
bably exceed 5 per cent.

(4)	Hand-Stoking Avoided. — It seems impossible to
burn non-gaseous small coal if hand-stoking be employed
—at least so far as cleaning out the ash is concerned;
indeed, each time any part of the grate is cleaned in
this way, the temperature of the furnace lowers, and
the newly-added fuel is unable to ignite.

The annual general meeting of the Coal Trade Benevolent
Association will be held in No. 8 Room, London Coal
Exchange, at 1 p.m. on Monday next, February 14.

H.M. Minister at Buenos Ayres reports the publication of
a Decree approving a contract between the Argentine
Hydraulic Works Department and the German Coal Com-
pany Limited, of Buenos Ayres, for the supply of 6,000 tons
of American coal at the price of 14-25 dots, gold (£2 16s. 6d.)
per ton c.ii.f. It is stipulated that the fuel is to be either
Pocahontas or New River coal. Delivery is to be effected
at the port of Buenos Ayres, within 30 days from the date of
the approval of the contract. The total estimated value of
the contract is about ,£17,000.