November 3, 1916.

THE COLLIERY GUARDIAN

853

tonnage of washed product was thus increased in two
ways : by the increased rate of washing per hour, and
by the increased percentage yield obtained.

Certain subsidiary advantages were also recorded, the
consumption of washing water being reduced by one-
half—thus saving an expenditure of 75 kw. per hour
in pumping—the consumption of motive power being
reduced to that required for operating the screens and
elevators, whilst the running and upkeep were greatly
simplified, and the facility of regulation was particu-
larly appreciated, in view of the varied character of the
coals to be treated.

Although the Rheolaveur might not have proved so
greatly superior to the box washers had the latter been
specially designed for the purpose to which they were
being put at the time—this plant having been in opera-
tion for some years; nevertheless, it is considered that,
particularly for washing slack, the Rheoiaveurs will
always give more efficient classification than felspar
washers, for the following reasons :—

In the first place, the suction resulting from the
return stroke of the piston in box washers, inevitably
draws some fine coal in with the schists; box washers
require very careful previous screening of the coal, and
increase the quantity of sludge, by reason of the fric-
tion in the boxes; very fine particles (O/jj in.) are
partially removed by the Rheolaveur, but are left
behind by the box washer, whilst, when the dust has
not been screened out, the Rheolaveur carries particles
as fine as in. away to the settling tanks, these, how-
ever, being left with the schists in box washers.

The same colliery has since put down Rhdolaveur
plant for washing j/f in. peas, with equally satisfactory
results; and the extension of the system to |/1 in. nuts
is in contemplation. For sizes above If in., a slightly
modified form of the Rheolaveur has recently been tried
at the Esperance Bonne-Fortune Colliery, Liege, the
alteration being necessitated by the fact that the dis-
charge orifices for the schists had to be so wide that
they allowed too much water to escape. The diffi-
culty was overcome by making the Rheolaveur pocket

Fig. 11 —Rheo-Blowee.

Charbon a depoussierer = coal to be cleaned.

Poussier = dust.

Charbon depoussiere = cleaned coal.

with a submerged receiver for the schists, the latter
being removed by means of a conveyor (fig. 10).

It may also be mentioned that the Ateliers de Fives-
Lille have recently designed a “ Rheo-blower ” (fig. 11)
on the same principle as the Rheolaveur, for the pur-
pose of removing dust from coal previous to washing.
A test made with this apparatus at the Lens Colliery,
on 0/1 in. slack, containing 9 per cent, of very fine
dust (0/0-006in.) and 3 per cent, of moisture, gave the
following results:—Output per hour, 2,4001b.; dust
collected, 10-6 per cent, (containing 78 per cent, of
0/0-006 in., 20 per cent, of 0-006/0-02 in., and 2 per
cent, of 0-02/1 in.). The dimensions of the Rheo-
blower are 2 ft. 8 in. by 12 ft. by 4 ft.

Mr. A. 8. Tallis has been elected to a seat on the board
of directors of the Tredegar Iron and Coal Company Limited,
in succession to the late Sir A. Markham, Bart., M.P. Mr.
Tallis previously held the position of managing director of
the Markham Colliery.

In connection with the recently issued Home Office report
on electric signalling with bare wires, the quart size wet
Leclanche cell is recommended as having a high internal
resistance, and consequently limiting the current on. short
circuit. The report fails to point out that, according to the
Mines Act, there is no limit to the number of cells which
may be put in parallel, and it is by no means uncommon
practice to find a battery of 100 of these cells arranged in
series parallel to give a voltage within the limits of the Mines
Act, namely—25 volts. Any danger from sparking at signal
wires may be eliminated by fitting the bell magnets with
copper sleeves, and using a high resistance winding. This
seems to be the most simple plan, as it cannot be tampered
with. Some restrictions should be placed on the connection
of batteries in parallel. The insertion of a non-inductive
resistance in series with existing bells will probably be
generally adopted, but there is always a danger in case of
the bells not ringing properly that the whole or part of the
resistance will oe cut out. This represents the idea of a
correspondent of The Electrician.

THE NORFOLK OIL SHALES.*

By William Forbes-Leslie, M.B., F.G.S.

In England, oil is derived from kerogen shale, bitu-
minous shale, and shales containing both kerogen and
free oil, situated in strata belonging to the Jurassic and
carboniferous systems. The shales of Kimmeridge
(Dorset) have been sporadically worked from time to
time, but without any measure of success. More than
50 years ago, a company was formed to manufacture
naphtha paraffin grease, petrol varnish, paint, and
ammonia. Another company was formed at Alston
with the ostensible object of manufacturing mineral oil.
It was liquidated in 1872. Another was formed in
1876 for the introduction of carbonaceous residues left
on the destructive distillation of the shale as a substi-
tute for coal charcoal. All these companies were
unsuccessful, the attempts to work the shale oil fields
being premature.

Geographical Situation of Oil Shale Fields.

The geographical situation of the oil shale series of
the jurassic system in England comprehends a large
portion of the southern parts of this country. Its out-
crop is found included in the counties of Dorset,
Somerset, Wilts, Gloucestershire, Berks, Oxfordshire,
Buckinghamshire, Bedfordshire, Cambridgeshire, Nor-
folk, Lincolnshire, and Yorkshire. The exposures of
the series form a long sinuous line following the shore
of the upper jurassic sea. In Norfolk the series is
flexured, a spur of the outcrop passing northward under
the Wash, while the main line runs north-west through
Lincolnshire, to re-appear from beneath the cretaceous
overlap on the north side of the Yorkshire chalk wolds,
passing with eastward strike into the North Sea.

The oil shale series of the carboniferous system is an
integral part of the coal basins of England. Their
importance has in every case been overshadowed by the
coal seams and measures of which they form part, and
in many cases it is only due to there being an obstacle
to safe mining of the coal that we have heard anything
about the shales themselves.

Geology of the English Shale
Fields.

In England no bituminous
or kerogen shales of economic
value have been encountered
in rocks younger than the
jurassic. The third division
of the jurassic succession, or
the Kimmeridge clay, covers
extensive areas in the South
and East of England, extend-
ing from Dorset on the south-
west to the Wash, in a broad
continuous band, varying in
width. It is sometimes over-
lain by the second division, or
the Portland beds, of its own
system, but at times these and
the first division, or the Pur-
beckbeds, are eroded, or absent
through default in deposition,
and the exposed Kimmeridge
clays are covered unconform-
ably by cretaceous, tertiary, or
recent beds.

The chief historical example
of an oil shale basin of the out-
crop is that of Kimmeridge, in
Dorset, on the extreme south-

west of the Kimmeridge series,
where a lenticular depression is demonstrable, partly
exposed and partly concealed beneath cretaceous rocks,
although not in every ease beyond a workable depth.

On the north-eastern extremity of the outcrop, there
has been lately investigated another lenticular depres-
sion or basin” partly exposed and partly concealed
beneath a thin cover of younger rocks, the centre of
which is believed to be at, or near, the village of
Wormegay, in Norfolk.

Between these two points there are indications of
other Kimmeridge basins, both visible and concealed,
in the long and, in places, broadly exposed upper oolite
rocks, an investigation of which might probably disclose
included bituminous or kerogen bearing shales.

Oil Shale Basins of the Kimmeridge Measures.

Concealed Basins.—Presumptive evidence of the exist-
ence of at least two basins of the Kimmeridge measures
have been detected by the drill. For the purpose of this
paper, they may be called tire Wealden oil shale basin
and the Essex-Kent oil shale basin.

The Wealden Oil Shale Basin.—Situated in the county
of Sussex, and lies deep under a discordant sheet of
chalk, Wealden, and Purbeck-Portland beds. It con-
nects with the Kent oil shale basin across the Cross-
ness-Brabourne line, along which a series of boreholes
have demonstrated underlying Silurian rocks. Six bore-
holes have revealed its presence. One at Dover proved
44 ft. of Kimmeridge clay, containing horizons of bitu-
minous shales. Another at Elham proved 108 ft. with-
out penetrating the beds. Another at Brabourne gave
262 ft. of Kimmeridge clay; while one at Battle passed
through 1,273 ft. of Kimmeridge clay, containing
apparently rich bituminous shale. A boring at Pens-
hurst, near Tunbridge, proved 622 ft. without piercing
the Kimmeridge series; while at Pluckley, further east,
526 ft. of Kimmeridge beds were encountered without
passing through them.

The Essex-Kent Oil Shale Basin.—Probably covers
the greater part of the counties of Cambridge, Essex,
and Kent, and may be divided geographically into a

* From a paper read before the Institution of Petroleum
Technologists.

southern basin, the Kent oil shale basin, and a northern
one, the Saffron Walden oil shale basin.

Kent Oil Shale Basin.—The existence of an oil shale
basin in Kent is revealed by borings at Dover and
Elham and Brabourne, where Kimmeridge clay con-
taining bituminous seams was found in its correct strati-
graphical position, and also exhibiting signs of erosion
and default in deposition. These fragments of a great
period are capable of a correct correlation with the main
body of the series farther west and north at Penshurst,
Pluckley, and Battle. It is highly probable that as
the synclinal axis of the Kent basin is approached, the
Kimmeridge clays will be found in position overlying the
coralline beds. A connection between the Wealden
basin and the Kent basin is probably effected imme-
diately south-east of Brabourne, by way of Elham and
Dover. Connection with the Saffron Walden basin is
effected under the estuary of the Thames, and east of
the London palaeozoic platform.

Th e Saffron Walden Oil Shale Basin.—Includes the
greater part of the counties of Cambridge and Essex, and
portions of Hertfordshire and Suffolk. The position of
the Kimmeridge clays in this area is confined to, and
forms part of, the contents of a great syncline, situated
between the eastern edge of the London palaeozoic plat-
form and the presumed western edge of an axis of very
ancient palaeozoic rocks, directed approximately north-
west south-east, or more or less parallel with the folds
of the Charnian axis.

The head of the series lies near the surface in the
northern section, but as the trough is followed south-
eastwards, chalk and tertiary beds are brought over the
Kimmeridge, till the head of the series, if present, is
buried 400 to 1,400 ft. deep.

In the Saffron Walden boring no record is given of
any included bituminous shale seams, but it seems
improbable that where the conditions subserving their
establishment are proved to exist to the west of this
area in the Wealden basin, to the south of them in the
Kent basin, and to the east of them in the Norfolk basin,
they should be absent in the Essex syncline.

Exposed Basins.

Only two oil shale basins of the Kimmeridge outcrop
have been the subject of scientific investigation, the
Kimmeridge-Portisham basin in the county of Dorset,
and the Wormegay basin in the county of Norfolk.

The Kimmeridge-Portisham oil shale basin is situated
in Dorsetshire, upon the extreme south-western end of
the Kimmeridge outcrop, and has been so often
described, and so long known, that it requires no further
description.

Wormegay Basin.

The Wormegay oil shale basin is a new discovery, the
facts of which, resulting from recent investigations, have
not as yet been made public. It is situated in the
county of Norfolk, and whilst extent of the basin is not
yet sufficiently determined to enable a correct defini-
tion of its boundaries, it seems to follow specific
geological feature lines.

Topography of the Wormegay District.—The surface
of the county of Norfolk included within the limits of
the Wormegay oil shale basin is, in general, flat and
uninteresting. Fragments of greensand appear on the
surface of the Kimmeridge clays as outliers, which in
places confer a ridged and irregular contour upon the
surrounding country. On the eastern edge of the basin,
however, the outcrop of the lower chalk forms a pro-
minent landmark; while, if closely scrutinised, evidence
of ridges quite apart from those forming the outcrops
of the younger periods, or the remains of their erosion,
may be discerned, the ridges running parallel, and
having a suspicious general relationship with the rivers
Nar, Wissey, and Little Ouse.

Geology of the Wormegay Basin.—The surface of the
basin is found to be covered with deep soil, beds of
blown and recent sands, brick and boulder clays, and
gravel. Many of the small ridges are composed almost
wholly of moraine material, with a foundation of green-
sand, which they have helped both to erode and con-
serve. But in almost every case the natural valleys
have been deepened or gouged out by glacial action, the
higher ground being composed of moraine detritus.
Erratics are common, composed of granites, quartzites,
limestones, and various igneous rocks. The rocks form-
ing the floor of the basin belong to the third division of
the jurassic. They are composed of clay shales, sand-
stones, and limestones; in some cases these beds are
highly fossiliferous, and much trenched by inter-
cretaceous and pre-glacial water channels, containing
the remains of a great erosion of the chalk and green-
sand. In other places greensand is found in position,
occupying depressions or ancient riverine channels in
the Kimmeridge clays which must have resulted from
the elevation of this area in pre-cretaceous times, pro-
bably during the period when the Purbeck and Port-
landian stages were being laid down in other parts of
England.

Towards the eastern edge of the basin the lower green-
sand and gault, upper greensand and lower chalk suc-
cessively form the overlie of the Kimmeridge clays. At
Hoikham as much as 743 ft. of chalk and greensand are
interposed between the surface and the top of the
Kimmeridge series.

The visible or shallow stratigraphical horizons of the
Wormegay basin comprise the cretaceous rocks from
the lower greensand eastwards to the top of the lower
chalk, the Wealden and Hastings beds being absent in
these localities, and westwards the upper oolites, with
the exception of the Purbeck-Portlandian sub-stages,
which do not appear to have been laid down in the east
of England.

Investigations in Wormegay Basin.—Where denuda-
tion has exposed the Kimmeridge clays in the Wormegay
basin, evidence of oil shales being intercalated in these
clays has, from time to time, been demonstrated. Frag-