The Silly Season.

As the last stencil for the June B.B. has come off the typewriter, this one has followed it.  We try, as a rule, to keep a certain balance, wherever possible, between serious and humorous articles in the B.B.  If this issue – like the, last one – finishes rather too much on the humorous side, we apologise to the more serious minded of our readers.

“Alfie”

Old Inns of Bristol

Some time ago a select committee of B.E.C. members decided to conduct an investigation onto the hostelries of the city.  So much has happened during the last year or so around the central parts of Bristol that it was thought visiting members might waste valuable drinking time trying to visit some taverns which may no longer interest them.  For example, that ancient haunt of fiarios “The Rummer” is now a frightfully jolly establishment absolutely oozing with period pieces and historic bric-a-brac.

However, to the beginning of the tour.  The party met at the appointed hour in the upper bar of the Hatchet – that classical black and white timbered ale house in Denmark Street.  The lower bars appear to be somewhat proletariat in character and would not appeal to members except perhaps to those studying the more bizarre side of social anthropology.  The iron studded doors hide pimply faced adolescents with long hair, accompanied by a selection of bottle blondes for whom the prototype would probably be found in the Monroe-Mansfield group.  Upstairs, in the oak panelled lounge, the atmosphere was altogether different filled with gentlemen who – to judge from the walls – were so hard up that they would permit the ends of their old school ties to be removed for the price of a pint. It drips of the mess, chaps, after a jolly game of rugger – or was it hockey?

Leaving this delightful establishment, the party aimed itself in the general direction of the Rummer but one of the members became so stricken with the pangs of thirst on the way that the Drawbridge had to be visited.  Here was witnessed and interesting encounter between a ragged and unshaven gentleman and a barman.  The R. & U.G. was unsuccessfully trying to get a pale ale and a double rum with a pitiful collections of copper coins totalling 1/10½d which appeared to be poor old mans total assets – except for the large roll of crinkly greenbacks held in his grubby left paw out of sight of the barman.

Before venturing forth again, some thoroughly recommended cheese and salad mixture rolls were stuffed into the beer-holes of your select committee.  The Rummer – first licensed in 1241 – has recently set the vogue in steak bars, and amongst the many “smart” bars has an underground vault known as the Smuggler’s Bar.  The bar itself is a lifeboat and draught sherry barrels pour out their golden liquid ‘Shipped from Portugal to the port of Bristol by Bristol ships’.  How nice.

Next to the Rummer is another steak and stilton eatery and a large vault known simply as the Cellar. This has for some inexplicable reason a more genuine atmosphere than the snug ‘Smugglers’.  It is a large vaulted cellar, with a huge fireplace ornamented with muskets and cutlasses – one almost can expect to see Pepys or Sir Francis Dashwood descend the stone stair.  The only discordant note is the surfeit of pseudo-Spanish posters advertising jolly little sessions at some Plaza de Torros.  Viva el Bull!  Perhaps these should be tolerated for apart from draught Sherries they sell a very palatable draught Sauterne at 1/2 & 1/9 per glass which must be Spanish.  The Toby Bar on a higher floor supplies draught Chianti at 2/6 per carafe – about 8d per glass.

The evening ended on a discordant note in the Guildhall Tavern, where having complained about a greasy unwashed knife to the lady in charge, we were greeted with “What!  Five minutes to ten and you want a clean knife!”

                                    (Signed) G.Host, Inn Spectre.

Building a Belfry    Part Seven

(Those of you who are following this sordid epic will note that it tends to come out spasmodically – when we have nothing else to print.  The last episode appeared in the B.B. for March.

Meanwhile, what of the builders?  As the pile of building stone gradually accumulates a layer of moss, old motor bikes, caving gear, etc., do we find them just sitting idly by and doing nothing about it?  We do.

Gradually however, through the haze of tobacco smoke and the stew-fuddled minds of those concerned, an idea slowly seeps out.  Why not ask the local stonewalling expert for advice on the next move?  This is done, and after sorting out the relevant remarks from a mass of non-applicable data such as ‘sidle gently’ or ‘putting up between’ and back this ‘topping’, we arrive at the ghastly truth.

It appears that if we were very skilled – and it is forcibly pointed out to us that we are not – we could build the walls ‘only’ eighteen inches thick.  In our case, they would need to be at least two feet.  Furious calculation now shows that the enormous pile of stone we have collected will only be enough to build a chimney breast or possible a communal three-holer.

Once again, we sit round the stove, twiddling our thumbs with our minds in neutral.  Eventually someone speaks.  We will use concrete blocks eight inches thick and render the outside walls with cement (note how technical terms are beginning to creep in!)  Once this idea has percolated, we are all agog. We will use the stone for the end gables and have a full size Old-Fashioned-Mendip-Pub-Type-Fireplace in one of them.  At the other end of the hut we will have a small room for tackle.  The big room will be for changing in and storing caving gear. We will roof it with a gabled roof of corrugated asbestos to match all the other local houses.

While we are examining this plan for the inevitable snags, the prospective architect plays his master stroke.  With cunning expression he points out that, on suitable occasions, all the caving gear could be removed, a great fire lit in the O.F.M.P.T.F.; crates of the necessary stacked round the walls, and a damn nigh unbreakable, an amazing time could be had by all.  This dual purpose appealed instantly to the better nature of all present.  All that was now necessary was to obtain planning permission and conversations with the planning authority went something like this: -

B.E.C.: “We wish to put up a tackle hut made of concrete blocks with stone gables.  We feel sure that….”

P.A.:     “Hard luck!”

B.E.C.:  “Pardon?”

P.A.:     “Hard luck!”

B.E.C.:  “Why?”

P.A.:     “No concrete blocks.  Only natural stone.”

B.E.C.:   “We could pebble dash it with natural stone chippings.” (Note crafty use of technical terms.)

P.A.:      “No. The outside must be natural stone.”

B.E.C.   “(Thinking rapidly) “Did you say the outside?”

P.A.:     “Yes.”

B.E.C.:   “Then we could build the inside with blocks and the outside with stone?”

P.A.:     (Baffled) “Yes.”

At this stage, the B.E.C. became one up and the conversation gradually ascended to the roof.  It transpired, after cunning negotiation that we could have a corrugated asbestos roof provided it was concealed from the gaze of the ignorant by a suitable parapet.

Our consultant surveyor (Mr. Ifold) was next approached and after many threats was prevailed upon to prepare a plan.  This plan showed a building of hybrid construction which, with a bit of luck, should get future historians completely baffled.

A four page form was completed in triplicate (yes, it actually happens in real life) by the member who could write and was sent off with the plans.  We waited.  They came back passed!  A universal gloom spread over all of us as we realised that we should now have to leave the stove and actually build the place.

Barometers

Since Roger Stenner wrote his original article on ‘The uses of a Barometer in Cave Surveying’, quite a bit of discussion has gone amongst the more scientific members of the club. We now publish Roger’s latest memo on the subject and a reply by our Scientific Adviser.

Roger writes: a physicist in the N.P.C. reckons by his calculations that a shaft fifty feet high with a waterfall occupying 0.1% of the volume would give a reading out by 50ft, and suggested several pot in Yorkshire where the writer would be well above the 0.1% even in dry conditions.  I tried to get his reasons and he said something about the compressive effect of falling water.  I couldn’t understand the whole of his reasoning which I thought depended on statistics, and would only have an effect when water reached terminal velocity, but he may have something else in mind.  I did however, have a go at winds through an aperture, and having got dug into it, I’ve got something which seems to be reasonable.

Assume limits of pressure change (small) the air is not compressed.  Now consider a restriction of cross sectional area A, length S and a difference of pressure across the aperture of DP.

Assuming a plane front, a mass of air moves across the aperture accelerated from zero velocity to a velocity V along the disturbance S in time t.

If the front of air travels the distance S in time t, the volume of air moved will be AS.

Thus the mass of air moved in time t will be ASr where r is the density of the air.

The force causing the air to move will be F=ma=ASra where a is the acceleration of the mass of air.

But V=at and thus a=V/t

Also S=tV/2

Thus 1/t=V/2S and a=V2/2S

Therefore F=AV2r/2 and dP=rV2/2

A dimensional check on this equation gives a correct result.

Taking a rough value of air density of 0.0013 gm/cc and a wind of 4mph or about 200 cm/sec dP becomes approximately equal to 28 dynes/sq.cm.  I realise that this neglects viscosity and compressibility of air, but it can’t be too far out, unless I’ve got the figures wrong or forgotten something else.

This result as it stands would mean that barometric readings would be seriously disturbed by such a draught, to say nothing of the waterfall effect mentioned earlier.  Our tame scientific adviser has not commented on the waterfall effect, feeling that the information given was not definite enough.  He has, however, sent us in the following about the effect of draughts: -

Let us consider, for arguments sake, a tunnel 2ft in diameter and 10ft long.  This is intended to approximate roughly to the Wind Tunnel in Eastwater.  It is appreciated that longer and narrower tunnels exist, such as the Drainpipe in Goatchurch, but the Wind Tunnel is notorious for the draught which often exists there.  The previous author’s calculation for a 10ft (300cm) tunnel gives a change in pressure of 300x28 dynes.  This is equal to 8.4mb.  Under cave conditions, this corresponds roughly to a change in altitude of 310ft which would amount to a gross error in surveying at a wind velocity of only 4 mph and would probably make you ears ‘pop’.  As the wind velocity through the Wind Tunnel is often appreciably higher than 4 mph, we would certainly have heard ears popping and probably burst eardrums if these calculations were correct.  In fact, investigation shows that the previous author has calculated the pressure drop to produce an acceleration of 4 mph/sec and not the pressure drop required to maintain a steady wind velocity of 4 mph.

It is unlikely that the B.E.C. will ever be rich enough to own a sensitive barometer of its own, and it is virtually impossible that it will ever have two, therefore, with one borrowed instrument, it is wise to choose conditions of atmospheric stability, so that small changes in external barometric pressure can be corrected on the assumption of a linear rate of change with time.

The “Machinery’s Handbook” gives a formula and a set of tables for pressure drop in pipes under steady state conditions and we find from the table that the pressure drop for a velocity of 600ft/sec on our tunnel is 0.0017 ounces/sq.in which cab be translated as an error in height of 2½ inches for a wind of 7 mph.

Apart from the initial assumption of a “standard” tunnel, we have merely proceeded via tables and a little arithmetic to a result which shows that a 7 mph draught can be neglected for all practical purposes.  We must now consider two other factors.  Is a wind of 7 mph high or low for the real Wind Tunnel in Eastwater? And is it reasonable to assume that the real Wind Tunnel is as smooth as a metal air pipe? We feel that in many places underground and that even if the roughness of the cave wall introduces a factor of two or three, this is still only an error of about 6 inches.

Editor’s Note:    It would appear that the use of a single, accurate barometer: provided sensible precautions are taken, has still not been shown to lead to significant errors in cave surveying.  We should be interested to hear from any readers on this subject, as a new type of accurate pressure measuring device will shortly be available, and there is a possibility of borrowing such a device for cave surveying.

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