Notes on Cave Surveying Part 3.

by  S.J. ‘Alfie’ Collins.

The instruments described in Part 2, and the method of surveying which uses them, may be used on surveys raging from a simple surveyed sketch to an accurate and detailed survey.  The C.R.G. gradings for magnetic surveys are as follows:-


Bearings: Pocket compass graduated to 10 degrees.

Distances: Marked string or stick.

Elevations: Not measured.

This will produce a rough plan, a little more accurate than a guesswork drawing of Grade 2 standard.


Bearings: Prismatic compass reading to 1 degree.

Distances: Measuring tape or marked cord.

Elevations: Not measured.

This will produce a better job than Grade 3.  Again only a plan can be drawn.


Bearings: Calibrated prismatic compass.

Distances: Metallic or Steel Tape.

Elevations: Clinometer.

Complete plans and elevations may be drawn from data compiled by this method.


Bearings: Calibrated prismatic compass on tripod.

Distances: Steel tape or Chain.

Elevations: Clinometer on Tripod.

The maximum accuracy attainable from a magnetic survey may be reached by this method.


A Magnetic Survey.

Returning now to the use of these instruments in a magnetic survey, let us imagine that a small portion of a cave is required to be surveyed, consisting of a passage which forms a small loop in the side of a main passage.

A good plan is to draw a preliminary plane to C.R.G. Grade 2 before starting the survey proper.  Taking a note book down the cave, the rough plan shown is drawn on the next page.

A centre line is to be carried out on this passage, by methods described in Part 2 to the standard of Grade 5.  A portion of a survey such as this is called a TRAVERSE.  In this case, since the traverse forms a continuous loop, it is known as a CLOSED traverse.  The next part of these notes will describe the surveying operations.



How are the mighty fallen!!!  A little bird whispered that Pongo now prefers Courting to Caving!  A gun is ready to shoot the little bird if the rumour is not factual.)

Congratulations to Tony Johnson on his engagement to Miss Mary Edwards of Plymton.

And also to John (Menace) Morris whose wife presented him with a son/daughter (???) about four months ago.


It has been suggested that a ‘Can anyone tell me’ series be started in the BB.  I feel that this is an excellent idea and will do a lot to spread the specialised lore of individual members amongst the rest.  Therefore, anyone with queries under the above heading is asked to send then to the Editor.  Questions can be on anything connected with caving, climbing, archaeology etc., or to do with the club itself; names of those submitting the questions must be included, but will not be printed unless the person submitting the question so wishes.


To start the series here is a question submitted by the originator of the idea: -

“Can anybody tell me why: -

Priddy Barrows are built in two groups of eight (I know there are only seven on one side now but one has obviously been flattened), and, if they were burial mounds, where was the settlement, or whatever it was called, that they served?”

“Why are the above called ‘Priddy Nine Barrows’ seeing that there are only eight?"

“Why are there no ‘Long Barrows’ in the area?”

“The Priddy Barrows are not the normal ‘hump’ type.  I believe that there are several types of Round Barrow, Disc, Bowl, and mound to name three.  What determined the selection of barrow type?”

Here is a final question for this month:-

“Why are so many Roman (& other) coins found?  Were the Romans (& Romano - Brits) so well off that they could scatter their wealth all over the country or did coinage mean so little to them that they very seldom retrieved that which they dropped?”

Over to the experts.  All answers to these questions, either theoretical or factual will be printed in subsequent issues.  I  propose to divided the questions into groups so that the subject matter is similar for all questions on any particular month, Ed.


By ‘Alfie’

Observe the latest electronic dodge
Resulting from the onward march of Science
As demonstrated at the Hunters’ Lodge.
The portable recorder - Brooks Appliance;
While cavers sing a thread of stainless steel
Is passing through the guts of this machine
Recording many verses of ‘Mobile’,
‘The Farmer’s Boy’ or ‘Little Angeline’.
Next morning, at the turning of a switch,
The singing and the jokes again you’ll hear
The merry clinking of the glasses which
Are gathered for another round of beer,
No use asserting ‘On my honour bright
I was sober as a judge last night!’


Quite motionless he is in armchair deep
No honest beer could deal him such a blow.
Enfolded in a stupefying sleep
The demon ‘Triple Vintage’ laid him low,
What is this brew that incapacitates,
Sends stalwart cavers early to their beds
To slumber till its grim effect abates,
Upsets the tum and turns blue litmus red?
A bottleful you safely may imbibe
And still remain to drink a bottle more
Three bottles you probably survive
No caver yet, has got away with four,
One thing is sure - four bottles and I am
Quite liable to be as bad as Lamb.

4th. June 1955.

In which Eric (Doc) Houghton and Ron Newman lose a large Mountain for three hours, and having found it, are blasted off it again.

Cloud base was almost down to road level when we set off for Glyder Fach, and it took us three hours to find it.  The inevitable wind and rain were putting on their usual performance, but we were comforted in the knowledge that in about an hour we should be enjoying that comparative shelter of Chasm Route.

Following the stream up to Llyn Bochlwyd, we turned off to the left to ensure that we should strike the base of Glyder Fach well to the left, so that all we than had to do was to skirt its base to the right until we came across the Alphabet Slab, which I would readily recognise as soon as it loomed out of the mist.

Sure enough, in its due season, the base of a mountain appeared, so we turned to the right and followed it round.  After what appeared to be a longer walk than usual, the clouds suddenly dispersed for a very brief interval, just sufficient to reveal three amazing things: firstly, the ground ahead fell away instead of continuing to rise; secondly, there was no sign of Llyn Bochlwyd! and thirdly, there was a road ahead and below.  We were really gazing at the main Holyhead road from the upper part of Heather Terrace, having wandered around Tryfan for some considerable distance.  Without a second thought I concluded that we had followed the base of Glyder Fach right over the Col, and were now heading down towards Llanberis:  We had either struck Glyder Fach too far to the right originally, or else we had passed the Alphabet Slab unknowingly in the mist.  (Non-climbing section members should consult O/S map of Snowdonia, otherwise they miss all the funny part of this episode).

So!  The solution was easy – just turn around and retrace our steps, keeping our eyes open for the Alphabet Slab.  As we proceeded, part of a mountain face appeared occasionally through the mist on our left.  I remember remarking that it looked familiar, and concluded that is was Gribin Ridge, being just where it should be according to my calculations.  It was, of course, our lost mountain.  After some time on our new course, it became apparent that all was not correct: we were on gently sloping pastures instead of steep scree slopes. Our true position now was getting on towards Wrinkled Slabs on the west face of Tryfan.

In despair, we retired to the shores of Llyn Bochlwyd and ate a dismal snack, while I glared balefully across at the ‘Gribin’.  Suddenly the penny dropped: just above the scree slopes of my Gribin, and just below the cloud was a large triangular slab, Eureka!  The lost was found!  It was the Alphabet Slab of Glyder Fach, looking completely different from a slightly different angle and without its usual visible background of cliffs.  We set off towards it hurriedly, fearful lest our elusive goal vanish again.

We led through up a very soggy, streaming Alphabet Slab via Beta and pressed on up an equally soggy and streaming Chasm.  However, the going was strenuous, especially one diabolical variation devised by Eric, and we soon warmed up.

On the seventh pitch, which I had just led, the blasting occurred.  There was absolutely no warning; no tense feeling in the air, no bristling of hairs on back of neck.  I was in the act of belaying when there was a most appalling flash and a deafening crack simultaneously.  This was followed immediately by booming roars reverberating all around, a definite smell of burning, rather like the smell of burnt cordite on a rifle range, and the hum and clatter of falling rock.  Eric, belayed in the gully below, had disappeared behind a large boulder, and I joined him in a split second later by whipping the round a knob of rock and free-wheeling on my stomach down the pitch I had just climbed, braking on the rope.  As we huddled together there, stones continued to fall, some of them bouncing on top of our boulder.

A few seconds later a ferocious hail-storm began; fortunately its ferocity was matched only by its brevity.  Having had previous experience of electrical storms on mountains, I urged rapid retreat as soon as possible, and Eric did not appear inclined to argue.  As soon as the hail had stopped, we began to beat the record for rapid descent.  But even this consolation prize was denied us, for Eric got the rope stuck roping down a steep bit, and the time taken to climb up and recover it delayed us considerably.  We got very wet coming down.

Back on the road again, drinking tea, the sun shone, the birds gang, our sodden clothes steamed on up, and all the mountains, devoid of clouds, glistened in the still air.  Every feature of Glyder Fach was clearly visible.  We concluded that fate had not been on our side today.

Ron Newman.