Contents
Annual General Meeting
The AGM will be held at the OLD DUKE (in the upstairs
room) October 5th. 1968 at 2.30 p.m.. The Old Duke is opposite the Landogger
Trow.
Nominations for next years Committee must be sent to Bob
Bagshaw (
the latest. As far as it is known at the
moment only Alfie Collins is retiring from the Committee all the others
(Bagshaw, Tilly, Thomas, Welch, MacGregor, Townsend, Petty and Irwin) are
automatically nominated as per the club constitution.
Annual Dinner
At the Caveman Restaurant October 5th at 7.30pm. PRICE 22/6
each.
Menu
Soup
Trout
a) Roast turkey etc.
OR
b) Braised Hare, half Pigeon and chopped Ham etc.
Sweet
Cheese & Biscuits
Coffee
There is a choice of the main dish. IF YOU WANT Braised Hare etc. dont wait
until the evening itself get in contact with Bob Bagshaw and let him know how
many tickets you require send the money with your order. If you dont tell Bob which meal you want you
will find yourself eating
Transport To Cheddar.
Bob is prepared to organise a coach from
on the way. Members and their guests
wishing to travel on the coach should let Bob know as soon as possible so that
the booking can be made.
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Hon. Sec: – A.R. Thomas,
Somerset
Editor: – D.J. Irwin,
Road
BS3 1QA
Club Headquarters: – The Belfry,
Road
Notes on the Structure of Mendip Part 2
by
Blackdown
Welch has aptly described this structure as resembling a
molar tooth on its side, the root pointing to the west. Over folding on the northern limb has produce
vertical and even inverted strata, the latter accounting for the limestone
outlier at Churchill. The western end of
the core is overlain by post-Carboniferous rocks in orange-red (f6) when the
area was presumably a bay bounded by the limestone outcrop. Where the orange-red is blue-dotted it indicates
the beach deposit conglomerate which often contains such large boulders of
Carboniferous Limestone that it can be mistaken for that rock in small
exposures. Where the Shale/Black Rock
Limestone boundary is exposed narrowly on the steeply dipping northern limb, it
crosses the Twin Streams above Burrington. The shales swing round the nose of the feature to Charterhouse where the
outcrop broadens owing to the more gradual dip of the strata and forms the low
marshy ground just north of the Lower Farm.
Its junction with Limestones gives rise to the well-know
swallets of the area. Further west, a
swallet is mentioned in the literature as being within the limestones of the
Shales succession to the north of Tynnings Farm. The Shales form the lowest part of the Hale
Coombe and the boundary is mapped as far west at
Off the nose of the pericline, and in limestones much higher
in the succession, the Lamb Leer Fault shows a displacement of strata of 200ft.
in the cavern.
North Hill
Overfolding here has produced the Harptree outlier in the
same manner as the Churchill outlier off Blackdown. In addition, it seems as though the western
end of this pericline was held up by the nose of Blackdown while continued
pressure from the south-west split North Hill along the Stock Hill and Biddle
faults, the rocks between the two having been displaced upwards. East of the road from Mineries Pool to the
Miners Arms deposits of conglomerate overlie the Carboniferous and older
rocks. However, the Shale/Limestone
boundary swings round from the Stock Hill Fault just west of the Miners Arms in
a rough semi-circle interrupted by the Priddy Fault(s) to rejoin the Stock hill
to the east of the Mineries Pool. The
faulted junction to the north-east of Priddy takes in Swildons and Nine Barrows
cave systems, while both Eastwater and St. Cuthberts enter at the unfaulted
junction, each under a low cliff of Black Rock Limestone. Between Stock Hill and Biddle Faults the
junction runs close to Cuckoo Cleeves and ends on Tower Hill in which area it
is reported to be marked by a line of swallets.
Waldegrave Swallet, in the beach conglomerate, is cunningly
contrived to deceive as the section of bedded limestone at its head is a
displaced limestone boulder(s). Just
east of the Stock Hill Fault, it is almost in the centre of the uplifted
sandstone core encroached upon by Conglomerate and a good half mile from the
nearest limestone outcrop. All the same
in 1950, a depth of 28ft. of water worn limestone was reported although no
water was seen in the swallet at the time.
Pen Hill
This structure was likewise split by both Biddle and Slab
House Faults and at least the portion to the east of the Biddle Fault forced
so hard against the eastern flanks of North Hill pericline that limstones were
fractured and driven over each other along the Emborough Thrust and the Lower
Limestone Shales appear to have been squeezed out altogether east of
Hillgrove. Only a patch of the Shales
survive to the south-west of Whitnell Farm. West of Hill Grove a very narrow band of steeply dipping if not inverted
Shales extends to Rookham. The
south-western edge of Pen Hill pericline has more recent rocks banked up
against it, the Shales only appear to the West of Horrington. Across the Biddle Fault they occupy a wide
band of marshy ground to Nab House, dipping under Black Rock Limestone all the
way.
Beacon Hill
Only the western end of this pericline appears on sheet 280,
and plenty of displacements are shown. Further east, in the Heale area, the fold is split along north-south
lines, the eastern section of the southern limb being thrust forward and
overfolded on top of the northern limb to form the famous inverted Coal
Measures klippe at Vobster.
Of Lower Limestone Shales, the railway cutting north of
Maesbury Station contains the classic section described by Sibly (1906, p338)
comprising the top two-thirds of the series.. (It is interesting to note that he comments Maesbury, mis-spelt Masbury
by the Railway Authorities). Some 600
yards west of the station the Shales/Limestone boundary is terminated by a
fault. To the east, the boundary,
sometimes faulted, sometimes obscured by superficial deposits, runs through
just west of Whatley. (Details of these
eastern outcrops are described from a map published by Welsh in his paper of
1933). The southern limb has a few
stream exposures of the Shales in the Thrupe area and the Shale/Limestone
boundary has been mapped north of Waterlip and south of Heale. Along the Heale fault, to the west of the
Heale-Downhead road, small exposures of the junction have been mapped and the
swallets have been indicated (Welsh, 1933, p22). East from Downhead the junction is displaced
to the south in Asham Wood and its finally obscured some 400yds. S.E. of Dead Womans
Bottom. A minute area showing the
junction has been mapped in Whatley Coombe just easy of Coombe Farm.
A mention of the spectacular Mendip gorges is appropriate
were they formed by collapse of underground caverns or by normal stream
downcutting? Or by both? An ingenious
theory put forward by Reynolds (1927, p3) on account of late Ice Age deposits
found within caves in the lower parts of the gorges and streaming from the
mouths of these gorges is that melt waters cut the ravine before the ground
water was sufficiently thawed to permit underground drainage.
It will be noticed that no mention of Vaughans zonal
classification used as the basis of Welchs mapping appear in contemporary
descriptions or on maps, although it was used in the Regional Guide (Kellaway
and Welch) of 1948. In Kellaway and
Welch (1955) a comparison of the Lower Carboniferous rocks of Mendip,
was made. Unfortunately, it was found
that the rocks of the
area could not be described satisfactorily in terms of the zonal
classification, moreover, the required fossil assemblages were not everywhere
present, hence it was necessary to re-classify on a different basis. This was done largely on the physical nature
of the rocks themselves, and as the result was in good agreement with the zones
where they could be identified, the alternative and more universal
classification was adopted.
A similar, but farther reaching, problem arose with regard
to the Lower Limestone Shales. In the
Sandstone and the Lower Limestone Shales which do not occur on Mendip or in the
Lower Limestone Shales in the Carboniferous System, the base of which had originally
been ascribed by Buckland and Conybeare (1824) to the base of the Shales. Hence the passage beds are
Carboniferous. Where they appear in the
Portishead area, however, they are inseparable from the Old Red Sandstone by
the nature of their deposition with the O.R.S. beds. Moreover both the passage beds and the Shales
where they occur in North Devon and
Old Red Sandstone. Quite apart from
this, the top of the Old Red Sandstone in the
where there are no passage beds, contains fossils which are found in the Lower
Carboniferous rocks to the south.
There is, therefore, a considerable argument for the
transfer of the local Old Red Sandstone Carboniferous boundary to the base of
the Black Rock Limestone.
As there is already evidence (Green and Welch, 1965, p.171)
that the Old Red sandstone and Lower Limestone Shales may be in hydraulic
continuity in two localities on Mendip, it is perhaps fitting to conclude by
lending speleological support to the argument for altering the established but
debated boundary between the Devonian and the Carboniferous Systems in the
area.
BLACKDOWN N. Limb outcrop narrower because of steeper dip
NORTH HILL N. Limb out outcrop inverted.
PEN HILL N. Limb without shales in region south of thrust
Sketch Sections To Account For Variations In Northern
Limbs Of Periclines
Bibliography
Buckland, W.
and Conybeare, W.D. 1824. Observations
on the south-western coal district of England. Trans. Geol. Soc. (2) 1,
210-316.
De La Beche,
H.T. 1846. On the Formation of the Rocks
of South Wales and South-western
Green, G.W.
and Welch, F.B.A. 1965. Geology of the
Country around Wells and Cheddar. Mem. Geol. Surv. 1 inch sheet 280. +=
Kellaway,
G.A. and Welch, F.B.A. 1948.
and Gloucester District, 2nd edition, British Regional Geology, Geol.
Surv. +=
Kellaway,
G.A. and Welch, F.B.A. 1955. The Upper
Old Red Sandstone and Lower Carboniferous Rocks of Bristol and the Mendips
compared with those of Chepstow and the
Kellaway,
G.A. and Welch, F.B.A. (Reynolds, S.H.) 1927. The Mendips. Geography, 13, 169-76.
Reynolds,
S.H. and
A. 1911. Faunal and Lithological
Sequence in the Carboniferous Limestone Series (Avonian) of Burrington Coombe,
(
Sibly,
T.F. 1906. On the Carboniferous Limestone (Avonian) of
the Mendip area (
with especial reference to the Palaeontological Sequence. Quart. J. Geol. Soc., 62, 324-80.
Carboniferous Limestone of the
Area. Quart. J. Geol. Soc. 61, 181-305.
Welch,
F.B.A. 1929. The Geological Structure of
the
Welch, F.B.A.
1932. The Geological Structure of the Blackdown Pericline. Proc. Bristol Nat. Soc. (4), 7, 388-96.
Welch, F.B.A.
1933. The Geological Structure of the
Geological
Map I inch Sheet 280 (Wells), 1963. +=
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Ed. Note: – The publications marked thus + are in the BEC
Library.
Those marked = are currently available.
Swildons – Duck Two
by Phil Kingston
As is well known, Duck two is now a sump of length 15ft.,
with an airspace some 8ft. in. It can be
free dived providing the following instructions are carried out. Going downstream: – hold the guide wire in
your RIGHT HAND and dive for 8ft. At
this point you should reach a fair sized airspace. Transfer the line to your LEFT HAND and a
dive of 6ft. will bring to the other side. These instructions should be reversed on the return journey. If the airspace is missed on the return
journey it is best to continue, feeling for the widest part.
I do NOT RECOMMEND the sump unless the person has attempted
a similar sump (i.e. Swildons 4).
The grey areas are tight sections
Caving Log
Edited by Keith
Franklin
This period saw the commencement of the St. Cuthberts
Caving Log, which is intended should be used exclusively for trips down St.
Cuthberts Swallet. Will all leaders
note that they have to sign, as well as all members of their party, before
descending the cave, the trip is to be written up afterwards. In this way all information will be in one
place and should make the job of collating and abstracting it easier I think! So lets deal with St. Cuthberts First. There were 24 trips down the cave, of which
17 were working trips mainly on the dining Room Dig, which has changed out of
all recognition (rumours that Wig has shares in the London Underground or the
Channel tunnel are completely unfounded!).
Other work trips include surveying and sporadic digging in
various sites in the cave. M. Calvert
made a preliminary study of bugs in the maypole Series and reports evidence
of recent visitations so leaders, who believe in the supernatural, beware. The cave shows little change from the
flooding in July, except for the Sump silting up (work will be commenced there
again shortly) and some differences in Continuation Chamber and Tin Mine which
may produce some positive results. There
were only 4 tourist trips with one guest leader trip and these, together with
11 general interest trips make up the total of 24.
Going on to other caving activities of the BEC we find
Swildons has attracted the usual quota of attention with a total of 18
trips. Nearly half of these were
concerned with
equally distributed around the rest of the cave. Probably everyone knows about the 40ft. and
other changes in top Swildons but perhaps it is worth noting here that Duck Two
is now a 15ft. sump and it is not considered a safe dive, although there is a
line through it.
G.B., after suffering from the visit of the BEC Committee,
is now subject to water sampling and tracing by R. Stenner there are no
results yet! Roger has also taken
beginners down various Burrington caves and, I must hasten to add brought
them back again. Hunters,
Pinetree Pot, Little Neath and Dan-yr-Ogof each had one visit from BEC members
during the past two months.
Digging news show the closing down of two digs for the time
being anyway; namely the Bennett site and Emborough (another victim of the
flood). One new dig has been started,
for the BEC at any rate, in East Twin. This has been dug by various other people in the past so perhaps it is
time the BEC had a go!
Monthly Notes No. 16
By WIG
Notes from
Ireland
–
St. Catherine-Doolin
System several hundred feet of passage discovered by the UBSS. St. Catherines II first descended by
members of S.M.C.C. has been surveyed by Bob Craig (SMCC) and members of
cave is currently being explored by the Craven P.C. The length is about 1½
miles of deep water passages. One caver
commented that the swim of about 1000ft. made the
in Dan-yr-Ogof look pretty feeble! Continuation beyond the present network of passages looks almost
impossible. The vertical change between
sink and resurgence is only 17ft.
WCC. After close examination of the
sides of the depression a small dig was started in a rift in the field
above. A side rift was found having a
depth of 20ft. but with little possibility of continuation.
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Axebridge Caving Group has published a Grade 3 survey of
their latest discovery believe it or not- called FOOT AND CRUTCH SWALLET. Its
length is approx. 150ft. I personally
thought the alternative name for
bad enough but Foot and Crutch
!
MINESHAFT at
CHARTERHOUSE. A new mineshaft has
opened up midway between Tynings Sink and Reeds Grotto. Although is has slumped about three feet on a
previous occasion the recent storms caused the shaft blockage to collapse. The shaft is about 15ft. deep. At the bottom a passage runs in a N.E.
direction for about 200ft. and then N.W. along a fault for some 25ft. Apart from a few sheep bones there is little
of interest to the caver.
The new cave (see July BB) in Velvet Bottom is thought to
be a mine.
OVERHEARD IN
cavers son.
Little girl: Lets play mummies and daddies.
Cavers son: O.K. Ill be daddy and Im going caving.
Multiple Flash
By Jock Orr.
The first part of this article appeared in the March issue
of the Belfry Bulletin where it described the assembly of the flash control
box, with flash units, cables, etc.
To continue refer back to p.26 (and circuit diagram) of
March B.B. Assuming that somebody has now completed the assembly and wants to
know how the contraption works.
Testing The Control Box
ONE FLASH: Move switches A. B. & C. to UP
position. Plug in cable to socket No.1
and the other end into flash unit. Insert plug to bridge socket 2 & 3. Plug in camera contact cable OR manual firing cable to firing
socket. Press SW.1 to check the circuit
and L.1 should light up to indicate circuit is O.K. Fire PF.1 bulb from (camera or manually).
TWO FLASH: Follow the above procedure, but this time
plug in cables to sockets 1 & 2. Bridge socket 3. For THREE FLASH plug in cables to sockets
1. 2. & 3.
FOUR FLASH: Move switches A. B. & C. to DOWN
position. Plug in cables to any four
sockets. Bridge remaining sockets. Press SW.2 to check circuits and L. 2 should
light up to indicate circuit is O.K. Test fire four more bulbs.
FIVE SIX FLASH: Follow the above procedure. Plug in cables as required. Bridge remaining socket if using five
flash. Fire off another or six flashes
and hang the expense because you know the thing actually works. If it doesnt work then something is
wrong! Check everything and start all
over again.
WARNING: Six flash bulbs fired simultaneously in a
confined space generates a fair amount of light take care of your eyes.
NOTE: You can fire any number of flash bulbs from one to six with the switches
in the down position. Remember to bridge
the empty sockets. BUT! When firing only
one or two flashes on the switches in the down position your camera contacts
will be carrying a heavy jolt of current from the large capacitor at a pressure
of 45 volts. So use the down position
for one to three flashes on extended cable runs only, where you need the extra
voltage to push the current through the cable resistance.
Suitable cable is ordinary twin domestic flex in a pliable
plastic outer covering as used for table lights and such like small
appliances. Anything thinner than this
becomes difficult to untangle.
Use the small layer-type battery to power the Control
Box. They are compact, high voltage
batteries with a mere trickle of current output. The capacitor stores the trickle of current
and releases it in a pulse of energy which is pushed through the cable by the
voltage pressure.
A point of interest is that the ordinary battery capacitor
flash gun requires a pulse of 2 amps of current and a minimum of 4½ volts to
fire a PF.1 bulb. A parallel-wired
device to fire six flash bulbs would consume approximately 12 amps of current,
still at 4½ volts, resulting in a very rapid discharge of the battery.
The advantages of series wiring, which is what we are
concerned with in this multi flash outfit, is that the current required for six
flash bulbs is no greater than for a single bulb, although the voltage
increases proportionally to the number of bulbs used. The voltage of the batteries used in this
particular circuit is adequate even when part discharged and the small demand
on current will allow the batteries quite a long time of usage before they are
due for renewal.
Using The Multi Flash
Harkening back to page 26 of the March B.B. again, lets take
another look at the illustrations. So
far the 6 cables 7yds. long have been plugged in with the flash units and
tested. The wire 3 off plugs as shown
are of course the bridging plugs. This
leaves the mysterious wire 5 off each socket as shown and the 3 cables
14yds. long to explain away.
The 14yd. cables are simple extension cables for long runs
where required, and the sockets are used to make up the joins in cable layouts
for any particular lighting arrangement.
A look at the illustrations accompanying this issue of the B.B.
will reveal five fearsome type cable joins. But when you have it all figured out they only take a matter of seconds
to connect up. They are in fact a simple
system which enables the photographers assistant to adapt the cable runs to
suit any situation. After hours of
practice on the surface, that is.
Anyway, to get on with it. Have a look at figure F. It
represents the Control Box with four cables plugged in and two bridges. The heavy lines denote the circuit inside the
Control Box feeding the cable sockets. The point of the illustration is to show that the circuit is a
CONTINUOUS LOOP, and this is the point to bear in mind every time you make a
join with the patent sockets. Figures
A & B are straight-through cable connections.
Fig. C
Figure C is a cable join with a flash unit directly off
it. Figure D can be used in two ways:
– a cable join with two spurs, or a cable termination in three spurs to take
three flash units. Figure E can either
be a cable join with spur to one flash, or a cable termination in two
spurs. This by no means completes the
combinations. The rest you can work out
for yourselves.
The sketch (Fig F) shows a typical lighting arrangement
using six flashes. Naturally cables
should be hidden from view.
Spur
to Two flash
Fig. E Fig.
D
FiGURE F.
FIGURE G.
The sketch (Fig G) is somewhat compressed to scale, but
this is the sort of layout for photographing a long way into a cave passage of
some similar situation. Caverns and pots
can get the same lit-up treatment. Obviously, in place of the usual flat effect, you are now going to get a
sense of modelling and perspective which will enhance your pictures no end and
please you enormously. Apply standard
indoor flash techniques and guide numbers as recommended in booklets on the
subject and you wont go far wrong. Good
Luck. Especially with the action shots.
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The hut warden has decided that all crockery and cooking
utensils will be removed from the belfry on week ending 10th. August 1968 until
further notice
bring your own!
Edison and
Oldham Lamp Spares.
Most parts of the
cell can be obtained from
CASEY BROTHERS,
Also in stock limited
parts. complete list in BEC Library.
West
Kingsdale
Master
Cave
A new survey has been produced of the
and can be obtained from Tim Reynolds,
3. Price 5/6 including postage. The survey is printed offset litho and is to
CRG. Grade 4.
Late News
Nine Barrows Swallet. John Cornwell and diggers have re-opened Nine
Barrows Swallet.
St. Cuthberts
Swallet. (Continuation Chamber): –
Phil Kingston and John Riley have inspected a new pool at the upper end of the
chamber. Previously the water could be
heard but not seen below the pebbly floor deposits. After the recent flooding the infilling was
so disturbed that a deep pool resulted. After a short time digging away a gravel bank it was found that there
was no continuation.
Annual Dinner
Draught beer will be available.