1028

THE OOLLIEBI GUARDIAN.

November 13, 1914.

these countries in October does no more than indicate
vigilance on the part of the British Customs authori-
ties, and the growing insecurity of the. mine-laden
North Sea. , This is a narrow view; the just conclu-
sion to be made from these figures, as Mr. Deacon
says, is “ that the increase in the exports of British
coal to the countries mentioned are fairly well within
the ordinary limits of variation of trade, having
regard to the decrease in German supplies, and that
no justification exists for the presumption that British
coal is being supplied to the enemy in important
quantities.”

k A point that does not appear to have occurred to
anyone is that a portion of the British exports to
Sweden may have ultimately reached Finnish or
Russian ports ; under no possible construction could
such a procedure be regarded as a breach of
neutrality.

A healthy feature of last month’s returns is the
trade with South America; 10,382 tons went to
Chile, 71,596 tons to Brazil, 46,143 tons to Uruguay
and 173.068 tons to the Argentine Republic.
Although these figures fall far short of the normal
requirements of the South American republics, they
are, in each instance, well in advance of the ship-
ments for September.

MANCHESTER GEOLOGICAL AND
MINING SOCIETY.

Geology of the Kent Coalfield.

. The ordinary meeting of the members of the society
was held on Tuesday afternoon last at the rooms of
the society, John Dalton-street, Manchester. The
President (Mr. Leonard R. Fletcher) occupied the
chair.

The following; gentlemen were elected federated mem-
bers : Mr. Moses Ashutst, West Leigh Collieries, Leigh,
Lancashire; Mr. Alfred R. Buffrey, Hanwood and Short-
hill Collieries, near Shrewsbury; Mr. . Percy W.
Taylor, Mayfield, Boothstown, Manchester; and Mr.
Richard Cheetham, Hill Crest, North-road, St. Helens.

The Chairman announced that in connection with the
papers open for discussion that afternoon, the hon.
secretary had sent invitations to be present to Dr. J. S.
Haldane, Dr. E. A. Newell Arber, and Mr. Herbert
Bolton, but unfortunately none of them were able to
attend. He was, however, pleased to be able to say
that Prof. W, Boyd Dawkins (Victoria University) had
consented to open the discussion on Dr. Arber’s paper
on “ Geology of the Rent Coalfield.”

Prof. W. Boyd Dawkins said it was a great pleasure
to have an opportunity of saying a few words on a sub-
ject which he had so often brought before the society.
In the first place, he desired to thank Dr. Arber for a
most admirable contribution to that very difficult but
interesting subject. They could not suppose for a
moment that twp scientific men dealing with the same
subject from two different aspects could agree on every
point. The view which Dr. Arber laid before them in
his communication was that of the palaeobotanist, and
the point of view he (the speaker) had taken in dealing
with the matter from the very beginning had been that
which presented itself to the mining engineer, the civil
engineer, and the physical geologist. He would first of
all address himself to the question of the addition to
their knowledge which had been made by Dr. Arber.
The author followed some of the Continental authorities
in dividing the coal measures in the Kent coalfield into
two groups, the upper or transition series and the lower
series which had the characteristic flora of the middle
coal ages, i.e., the characteristic flora of the main coal
measures of Lancashire. That, of course, was the
purely botanical point of view. When he began the
study of the Kent coalfield he took the evidence which
was presented by a consideration of the rocks of the
South Wales coalfield and the Somersetshire coalfields,
particularly that of Bristol. He was bound to say there
was no very considerable difference between them in
the actual grouping of the beds. The name which he
proposed, the Pennant, was based on the resemblance to
the Pennant series, which was the upper series in the
Somerset field. That was the equivalent of the transi-
tion series of Dr. Arber. The other series below the
Pennant, which he classified originally with the lower
coal measures of Somersetshire, was not for a moment
to be confused with the lower coal measures of Lanca-
shire or of Scotland. . They were quite distinct, and
Dr. Arber was perfectly right in putting them down as
belonging to the middle coal measures. With regard to
minute classification of coal measures, they h*ad first
of all to deal with the fact that they could not expect in
any ancient forest, or, indeed, in any modern forest, to
find a uniform flora. The difference between one flora
and another in almost all cases might be taken to be
represented by changes in the climate. He did not
think the botanist had yet got any further than dividing
the flora into three principal groups : the lower, the
middle, and the upper; and, therefore, he was not
inclined to think there was any essential reason for using

the term “ transition ” ^as Dr. Arber .did, , So far -as he
could understand by a comparison of Dr. Arber’s map
with his own, there was no very important addition
made to the knowledge already possessed about the field.
Referring to the paper 116 (the ' speaker) delivered in
1913, he pointed out that among the borings which were
carried out at that time was one at Ebbsfleet, which
revealed for, the first time the existence of the carboni-
ferous limestone, in that area. The whole of that was
covered with secondary rocks to a depth of 800 or 900,
and sometimes as much as 1,000 ft., and in that par-
ticular place the coal measures were 103 ft. thick, and
then the boring went right into the limestone. In
consequence of that, he put the boundary as shown on
his map. He took it that the carboniferous limestone
formed a rim round the field, at least on the north side,
just as it did in Somerset, France, and South Wales.
Dr. Arber drew a different boundary for carboniferous
limestone; he brought it right away to the bottom of
the sea, some couple of miles or more from the South
Coast. He (the speaker) failed to understand how Dr.
Arber could get evidence to justify that. That was one
of the main differences between Dr. Arber and himself.
After all, his opinion was, more or less, in the nature of
a guess, and the question must be left for further investi-
gation. With regard to the north-western boundary,
Dr. Arber took it up to an arbitrary line. For his own
part, he (the speaker) could not see his way to carry
those coal measures beyond the River Stour. His
reason for that was that there was a boring at Chilham,
in which they got into rocks which were not carboni-
ferous. He thought, therefore, that in all probability
the boundary of the coal measures to the north of
Kent ran along the line he had indicated. He had also
a point to note with regard to the western range. The
western range was altogether indefinite; it was as
indefinite as that on the east. He should like to add
this with regard to Dr. Arber’s plan. There was a
boring at Brabourne, in wdiich the Devonian rocks—he
took it it was proved they were the Devonian rocks—
occurred dipping at an angle*of something like 30degs.
Dr. Arber said there was no room between that boring
and the boring at Ellinge for all the coal measures,
right away down to the Devonian (including the carboni-
ferous limestone) to come in. He really did not know
what thickness Dr. Arber would estimate them at, but
if he took the dip of 30 degs. which was ascertained at
Brabourne, there was room for something over 23,000 ft.
in thickness of rock. At all events he was not extrava-
gant enough to ask for anything more than that, which
was a very big figure; and he thought the author was
mistaken in that very small point. The sections given
by Dr. Arber were an important contribution to their
knowledge on the subject. They knew not that the coal-
field had a bottom to it. In seven borings they had
struck the carboniferous limestone at a very consider-
able depth, in one case 2,500 or 2,600 ft. below the sur-
face, and in another instance 2,700 ft. That, of course,
was a very important fact.

With regard to th£ correlation of the seams, he was
entirely in agreement with Dr. Arber in the statement
that it was extremely difficult to identify those seams
over a very large area. The main mass of the coal was
undoubtedly in the lower parts, as could be seen by an
examination of the sections, but if they asked him
whether he could correlate them one with another, he
would have to confess that, though he had tried over
and over again, he had not been able to do it. If they
took, as he had done, 500 ft., starting from the base
line of the carboniferous limestone and working upwards,
they found in that 500 ft. a great variety of coals and
thicknesses. Coals in that field certainly showed a
considerable amount of splitting, and he thought Dr.
Arber was right in holding the opinion that the splitting
seemed to be rather greater than in most other fields.
He might add that he had noticed the same difficulty
in dealing with the Somerset measures; it was extremely
difficult to correlate some of the seams, and especially
in what were called the lower coal measures. One other
point he should like to note was the great thickness of
the coal. In one of the sections they had 50 ft. 7 in. of
coal altogether, distributed through 16 seams, the
maximum thickness of a seam being 7ft. 6in., and the
minimum thickness 2 ft. 6 in. He mentioned that just
as an illustration of the great riches in coal seams in
that most remarkable concealed coalfield. The maxi-
mum thickness of any seam of which he had any
record was something like lift. 2 in., but there was
one seam which had a thin parting of fireclay, where
the total thickness was 13 ft. 8 in. Those thicknesses,
so far as he knew, were very unusual, and he did not
know that in Lancashire, at any rate, they had any
seams of coal which possessed any such maximum thick-
nesses as those he had called attention to.

In conclusion, he should like to say it was a great joy
to him to see how the development of that field was
going on. He never expected when he sank the bore-
hole at Shakespeare Cliff and struck comparatively thin
seams of coal that they would develop into anything of
the kind which had been shown by the researches carried
on during the last quarter of a century. The whole
thing was, of course, very satisfactory to him, and he
considered himself very fortunate in having lived long
enough to see that particular pet bantling of his grow
and develop into a bird, which would likely be almost
as important to this country as a Prussian eagle was to
Prussia.

It might be interesting to the members to mention a
point he had worked out in connection with the Pennant
grit, following Sir Henry De la Beche and others. In ■
the Pennant grit there were massy conglomerates made
up largely of pebbles of coal, carboniferous sandstone,
carboniferous shale, and mudstones. As far as he
could make out, the coals first of all, before they got
into the conditions of pebbles, formed an ordinary coal
seam, and the mud banks, which were originally* accu-

mulated on the surface, had taken the shape of shale
and mudstones. The sandbanks had become consoli-
dated into sandstone. Then the whole of them were
lifted up and exposed .to the action of erosive agents
on the Surface—water in some shape or another. After
that those fragments were collected together and built
up into the mass of the Pennant grit. That was the
great characteristic, so far as he knew, of the Pennant
grit both in South Wales and Somersetshire, and it was
owing to that that he was able to identify—at least, in
his opinion, he had identified them—the upper series in
Kent with the Pennant grit of South Wales and Somer-
setshire. The point was this, that for that sort of thing
to happen, the coal must have been broken up and
destroyed from some pre-existing, coal measures. There
must have been older coal measures existing as coal,
sandstone, mudstones, and shale before those pebbles
could be made, and that implied a very enormous gap
of time between the deposition of the lower beds in that
district, and the deposition of the beds in which those
pebbles were found. How long that interval might be
he did not know; nor could he tell the exact horizon where
that break in time occurred. He had gone right away
through the whole of the series at Ropersole and at
Shakespeare Cliff, and in other places in Kent, but he
had not been able to trace it. He thought that that
was a very good point to note in dealing with such a
difficult question as the classification of a field such as
that in Kent. He noticed that Dr. Arber had had a
similar difficulty in finding a true boundary between his
transition series and his middle coal measures, and he
was not at all surprised at that. In fact, it was exactly
what he would expect to happen, because they might
have recurrent conditions bringing about at various
times the formation which Dr. Arber described as his
transition series. The exact horizon, the range down-
wards of those conglomerates, he did not know. He
had not been able to fix it in Somersetshire. But what
he had not been able to do in Somersetshire, Sir Henry
De la Beche had done in South Wales, where he had
traced some of those curious conglomerates far down
into the so-called lower coal measures—he was speaking
of those lower coal measures as representing the middle
coal measures of the district under consideration. He
just mentioned that in passing.

Prof. Boyd Dawkins displayed a specimen, which he
said was of very great interest to him. It looked like
an ordinary conglomerate, but when it was examined
carefully they would find that it was composed of little
rounded masses of mud which had been accumulated on
a sandy shore. The mud was now mudstone charged
with iron. The pebbles were imbedded in sandstone.
He was able to find that out because it was clear in the
large masses that the grains of sand had been pressed
into the mud, just as they saw little pellets of mud con-
taining grains of sand on the seashore to-day.

Mr. G. H. Hollingworth said he had only a little
knowledge of the Kent coalfield, and he had not studied
it from the same point of view as Dr. Arber or Prof. Boyd
Dawkins. It was the mining and the commercial aspect
that, generally speaking, he had had to deal with. There
were certain points in the paper under discussion in
regard to boundaries with which he did not agree. He
was, however, disposed to agree with what Prof. Boyd
Dawkins had said about the westerly boundary, because
it seemed to him there was ample room for the coal
measures and limestone to come in before they got to
the Devonian rocks. Taking the general line of the
strike as he thought it should be taken, there was a very
large area for coal measures and the limestone. In his
opinion, it was hopeless to attempt correlation in a dis-
trict like the Kent coalfield. The only correlation he
had been able to make—and that was very doubtful—
was that the seam worked at Tilmanstone and Snow-
down collieries was probably the same. The two places
were about three miles apart, but the characteristics of
the seam led him to the conclusion that it was the same,
and there was nothing to contradict that view. There
was, however, one peculiar thing about it. At Snow-
down they had not got outside the north-easterly dip,
but at Tilmanstone they had a south-westerly dip, and
still the line of the two collieries was almost exactly,
within a trifle, the same level. Then, with regard to
the northern boundary, he came to the conclusion some
time ago that there was not much worth having beyond
the Stour, but there was apparently a little to be got in
that part, because one colliery was now sinking for coal
just to the north of the Stour. The thing that struck
him all along had been what Prof. Boyd Dawkins had
emphasised that afternoon : the great similarity of the
Kent coalfield structurally to the South Wales coalfield
and the Pennant grits. In material itself, if they took
a series of sections, and compared them with a series of
South Wales sections, they would find a great resem-
blance. He agreed with the suggestion that the genesis
of the conglomerates was the deposition of the lower coal
measures, which were afterwards swept away. There
was no trace of the lower coal measures as they were
known in Lancashire, or of the millstone grit, but they
came on to the limestone from the middle coal measures.

Mr. Bramall asked, on the question of correlation,
whether Prof. Boyd Dawkins had read Dr. Arber’s
paper on the “ Wyre Forest Coalfield in Shrop-
shire.” In that case the author of the paper
gave many sections of different borings at
different collieries, and though they were perhaps only
200 or 300 yds. away, it was absolutely impossible to
correlate them. In one case they found a mine 6 ft.
thick, and in another case they did not find it at all, or
practically not. When Dr. Arber spoke of the transi-
tion series, he took it the idea was that they had been
deposited long after the old red sandstone. There had