- 90 -

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 (699 Wells Road, Bristol 4) by September 7th at 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. don’t 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 don’t tell Bob which meal you want you will find yourself eating Turkey!

` BELFRY BULLETIN

AUGUST 1968

Vol. 22 No.7 No. 245 CONTENTS: - Club Notes 90 Str. Of Mendip Pt.2 91 Swildons – Duck Two 95 Caving Log 95 Monthly Notes No. 16 96 Multiple Flash 97 __________________________________________ Hon. Sec: - A.R. Thomas, Westhaven School, Uphill, Weston-super-Mare, Somerset Editor: - D.J. Irwin, 23 Campden Road, Bristol. 3. BS3 1QA __________________________________________ TRANSPORT TO CHEDDAR.

Bob is prepared to organise a coach from Bristol to the Caveman calling at the Belfry 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.

- 91 - Notes on the STRUCTURE of MENDIP by Keith Murray PART 2

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 Crook Peak.

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. Cuthbert’s 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.

- 92 - 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 Stoke Lane to end 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 Woman’s 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 Vaughan’s zonal classification used as the basis of Welch’s 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, Bristol, Chepstow and the Forest of Dean was made. Unfortunately, it was found that the rocks of the Bristol 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 Bristol

area there are passage beds between the Old Red Sandstone and the Lower Limestone Shales which do not occur on Mendip or in the Forest of Dean. In the Avon Gorge section these passage beds were included within 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 Belgium show affinities with the Old Red Sandstone. Quite apart from this, the top of the Old Red Sandstone in the Forest of Dean, 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.

---------------------------------------------

- 93 -

- 94 -

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 England. Mem.

Geol. Surv.1 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. Bristol 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 Forest of Dean. Bull. Geol. Surv. Gt. Britain., No.9. 1- 21.

Kellaway, G.A. and Welch, F.B.A. (Reynolds, S.H.) 1927. The Mendips. Geography, 13, 169-76. Reynolds, S.H. and Vaughan, A. 1911. Faunal and Lithological Sequence in the Carboniferous Limestone

Series (Avonian) of Burrington Coombe, (Somerset). Quart. J. Geol. Soc. 67, 342-92. Sibly, T.F. 1906. On the Carboniferous Limestone (Avonian) of the Mendip area (Somerset) with especial

reference to the Palaeontological Sequence. Quart. J. Geol. Soc., 62, 324-80. Vaughan, A. 1905. The Palaeontological Sequence in the Carboniferous Limestone of the Bristol Area.

Quart. J. Geol. Soc. 61, 181-305. Welch, F.B.A. 1929. The Geological Structure of the Central Mendips. Quart. J. Geol. Soc., 85, 45-76.

- 95 - 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 Eastern Mendips. Quart. J. Geol. Soc., 89, 14-52. Geological Map – I inch Sheet 280 (Wells), 1963. +=

…………………………………………… 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. Cuthbert’s Caving Log”, which is intended should be used exclusively for trips down St. Cuthbert’s 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 let’s deal with St. Cuthbert’s 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

- 96 -

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 Upper Swildons, the others been 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, Stoke Lane, 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!

+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 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 Sheffield University.

MONTHLY NOTES No. 16 By ‘WIG’

AILLE RIVER CAVE (Co. MAYO). The 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 Green Canal 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.

FERGUS RIVER SINK This was again inspected by ‘Wig’ and Bob Craig plus other SMCC and 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.

+++++++++++++++++++++ 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 Contour Cave (i.e. Sludge Pit) bad enough but Foot and Crutch……!

MINESHAFT at CHARTERHOUSE. A new mineshaft has opened up midway between Tynings Sink

and Reed’s 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 BRISTOL: Little girl playing with well known BEC caver’s son. Little girl: Let’s play mummies and daddies. Caver’s son: O.K. I’ll be daddy and I’m going caving.

- 97 - 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 doesn’t 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.

- 98 - 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 photographer’s 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.

- 99 -

Spur to Two flash

Fig. E Fig. D

FiGURE F.

- 100 -

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 won’t go far wrong. Good Luck. Especially with the action shots.

- 101 - 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 Edison cell can be obtained from

CASEY BROTHERS, 72 Eccleston Street, Preston, Lancs. Also in stock limited Oldham parts. – complete list in BEC Library.

+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ WEST KINGSDALE MASTER CAVE.

A new survey has been produced of the Kingsdale Master Cave and can be obtained from Tim Reynolds, 23 Camden Road, Bristol 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. Cuthbert’s 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.