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
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
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 Smugglers Bar. The bar itself is a lifeboat and draught
sherry barrels pour out their golden liquid Shipped from
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 Rogers 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
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 cant be too far out,
unless Ive 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 authors 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 Machinerys 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.
Editors
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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