Before laser levels, and still widely in use, on building sites boning rods were used. These are the T shaped wooden stakes you will have seen on the edges of sites.
So make eight five foot long straight posts with a pointed end and a flat end. Lie them side by side and mark all of them at four feet from the flat end with a line.
Now on a wet autumnal day decide where you want the centre of your circle to be. Scoop out a shallow depression, six feet in diameter but only six inches deep or so and puddle the clay soil by dancing around on it. You may find a greasy auroc skin helps line the pool. If it doesn't rain enough fill the pool with water.
Around the edge of the pool space your eight posts equally and bang them into the ground until the marked line is level with the water. You now have a ring of posts whose tops are level.
Looking across from post to post it is then easy to set up other posts so their tops are also level.
And then you can decide that the top of your sarsen uprights should be so many feet above that level, and you can measure down into the excavations from your level to get the depth of the hole right for the length of the sarsen you have to hand.
As he says, simples. But I hadn't had it explained to me before so it had never occurred to me that that was how it could be done..
More on boning rods at http://www.pavingexpert.com/setout03.html
It's said that this is also how the Pyramids were leveled.ReplyDelete
Cut a 500-foot square, flood it with the Nile, then drive a million stakes of the same length down to the top of the water. Drain pool, dig to the bottom of the stakes, and ... we have a level surface to work from.
(Auroch skins were no doubt optional)
Nice one Tim! The simplest explanations are always the most likely and normally true. The Longman of Wilmington carries two such items - was he a stonemason?ReplyDelete
Lets look for a small dew pond in the centre of the circle?
There is a barrow at the high point just above the Long Man Robert. It's not a bowl barrow. Interestingly, there is a bowl type barrow just over the other side of the Cuckmere at the highest point in the area: Firle beacon (there's also an old water pond just to the east of that barrow). A whole series of neolithic barrows, at regular intervals of relative height, lead down along all the high points leading down (towards the Long Man) along that range of hills.Delete
There are also some smaller Saxon barrows interspaced about the area
You should pop down to the shop in Rottingdean Jon (being a Eastbourne resident?) - by the endof this month I should have finished the entire South Downs map series covering the 'Post Glacial Flooding' waterways including the Longman and barrows you describe - you may be surprised that it was an island during the Neolithic Period, hence their locations. It seems from the maps that the Longman was probably used as a marker to the entrance of the nearby harbour.Delete
Hence not a single barrow in the lowlands below - only Roman and Medieval sites.
Thanks Robert. Still near Eastbourne but don't live there any more. I haven't been to your neck of the woods for many years now, but have to admit that I would be absolutely astounded if that segment of the South Downs were was an island during the Neolithic Period.Delete
It's actually quite simple to calculate through reverse engineering!Delete
Take just take the west of the 'island' which would be Lewes (where I currently live) today its virtually dry, just a thousand years ago it was an inland river port and in the Roman period it was a deep sea port.
This is at a time when sea levels in the past were lower than today - so it's a fresh water harbour. The fresh water comes from aquifers under the ground which were clearly at a higher level in the past than today.
The highest point of groundwater in history is directly after an ice age when the equivalent of 40K inches of rain is washed into the ground swelling the aquifers. So by reverse engineering the height of the water known in Norman times and then estimated in the Roman period we can see how the environment looked almost at any stage in history.
So we know for sure that is region was a 'island' directly after the ice age - the more interesting and technical aspect is how long the water sat on the land and we can tell that from the prehistoric sites and the topology the landscape which clearly shows water erosion.
We can even prove it mathematically (like Fisher with Darwin's hypothesis) but using frequency and probability distribution analysis to confirm our results and then show it graphically - i.e maps.
I have also done this analysis for Wiltshire as well as the South Downs - so I have over two thousand prehistoric sites calculated and mapped.
Each on is above the predicted 'post glacial flood' plains.
'seeing is believing' as I tell the many geological and archaeological students from Brighton and Bournemouth who visit the shop.
So we know for sure that is region was a 'island' directly after the ice age - the more interesting and technical aspect is how long the water sat on the land and we can tell that from the prehistoric sites and the topology the landscape which clearly shows water erosion.Delete
Interesting ideas Robert.
Might be worth considering engineering in addition to the reverse engineering you have described: Calculate the water run-off rate for your scenario, very simple to do using standard fluid dynamic equations, and then work back to the supply rate that would be required from the inland rivers you have described.
The result that you will get will prove, one way or the other, whether or not your ideas are feasible.
Nice idea Jon - I'll take a look at that in the next few months!!Delete
But on reflection, I may have slightly undersold the difficulty involved in doing river flow calculations. In your case, I would strongly recommend that you start by using empirical methods to get an initial idea of how likely the arrangement you propose is: It will not take long to get an answer to this.
Hence the months rather than weeks estimation.Delete
But using a known better source of information such as the Thames (the thames barrier carries monitoring devices for flow rates) we can get some very accurate statistics. We also now know the extent of expansion of the Thames during the Mesolithic period (paid for from the jubilee extension project) so the prehistoric 'run-off' rate will be relatively easy to calculate and then we can apply it to a greater surface area, such as the Ouse in Lewes.
The problem will be identifying the sources and the aquifers that fed the Thames - that will take some time and maybe like Fisher a new type of mathematical process my need to be invented, to estimate the capacity of such bodies.
All interesting stuff Jon - who knows, as a consequence, we maybe able to calculate how much ice really was on Britain at the end of the ice age, rather than the current estimations?
The problem will be identifying the sources and the aquifers that fed the Thames - that will take some time and maybe like Fisher a new type of mathematical process my need to be invented, to estimate the capacity of such bodies.Delete
Capacity is easy to estimate in very rough terms: We know the levels of downland containment clays and so on: These allow aquifers to have sufficient head to feed streams. Once you've roughly calculated the run off rate, and roughly calculated the potential aquifer capacity, you'll know whether or not your proposals are feasible. You've put a lot of work into this theory, so before doing more on it, I believe that it will be very worthwhile for you to do this calculation at the earliest possible time.
And i'm sure when I have the time these calculations will be done and presented - sadly, it will not 'prove' the hypothesis outright just its plausibility.Delete
This is why I concentrated on other 'proofs' of concept before the maths - such as the clear evidence that the Caspian and Black seas were affected by the rise in groundwater which doubled their size although over a thousand miles away from the ice cap.
Clearly, if this much water was released after the ice cap - only the most indoctrinated academic would suggest that the same increase in water levels would not affect sites like Stonehenge and the South Downs.
So the maths is nice to have eventually - but when you look at Darwin's hypothesis which was eventually proven by Fisher - who remembers Fisher and the clever calculations he created to prove natural selection is mathematically possible?
This is why I concentrated on other 'proofs' of concept before the maths - .Delete
Interesting: I always look at the maths first, to firstly see if there are any flaws which make a proposed concept unworkable and then methods I could use to test (eg destroy) the theory.
And i'm sure when I have the time these calculations will be done and presented - sadly, it will not 'prove' the hypothesis outright just its plausibility.
What you might want to do is to approach a friendly retired civil engineer to see if he can help. If you can provide a substantially good reason to explain what benefit there would be to mankind in knowing about xxxx (eg what all the stones were about or whatever is your aim), then you're much more likely to get good quality advice than if you present it as solving a mystery. It really won't take long for a civil engineer to give you an independent confirmation, or otherwise, concerning your theory.
However it goes, good luck.
As he says, simples. But I hadn't had it explained to me before so it had never occurred to me that that was how it could be done..ReplyDelete
Cool isn't it? If you want to go a step further and create a levelling platform, from which other levels in the landscape can be determined, you have to find a high spot and build up the earth into a bowl shaped mound, a little like a bowl barrow.
But if you are doing this, there is one other innovation you can make to make your life even easier. That second innovation would be detectable thousands of years later, as distinct from the general landscape and other 'ordinary' mounds, using certain types of engineering NDT (non-destructive test) equipment . However, you can only confirm your findings by excavation: That type of NDT equipment is not something that appears to be used in archaeology as far as I know.
Out of interest, I took some of that NDT equipment up to a high neolithic bowl barrow and ran the tests. Certain parts of that barrow scored some tens of thousands of percent higher than any of the local control tests or even any of the vicinity tests (vicinity tests are places selected locally, specifically to try to produce a high false result)
The unfortunate thing about this type of test is that general knowledge of what it is could encourage amateur investigators to undertake confirmatory excavation. So I let my MP know (he's interested in archaeology and sent me an email asking what it is), but otherwise it's one of those things that has to stay buried so to speak.