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Widecombe History Group Talk March 2008

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Widecombe History Group Talk: Understanding Geophysics


The speaker this month was Penny Cunningham and she spoke about “Understanding Geophysics” with particular reference to our North Hall Project.

Penny explained that Geophysics is a way of looking at abnormalities under the surface of the ground without actually disturbing what is there.

Archaeological digs by their very nature, destroy much of the evidence that is being sought by the action of digging. That is why modern archaeologists prefer to have a survey of this kind before they start any physical exploration. Small exploratory trenches are dug when something of interest shows up rather than removal of a large area.

When local interest is shown in a particular site, as that shown by our group in The North Hall Site, a geophysical survey is often the first step. There is still much to be learnt in the understanding of what these surveys show and it is only with care and patience that a more full interpretation of the images can be realised.

At present it appears that much of the evidence of the resulting photographic images of such a survey does create, perhaps, could be, may be, possibly, etc. What is very clear is that by the use of these images the best possible site for an exploratory trench can be decided without a mass excavation.

The experts in this field are still learning how best to interpret what is shown. The main principal is to notice any change or disturbance in the magnetic field of the underlying strata.

The information data recorded by a geophysical survey has to be looked at in conjunction with the physical features of the site. The ‘humps and bumps’ of a site to an experts eye often tell of the possibilities of a site. Wide trenches (a moat?), flat areas (site of building?), raised areas (built by man as protection?), water courses (leats, ponds, moats, supply courses for mills etc?). If there appears to have been manual disturbance years ago, or there are documents recording existence of buildings or the like in previous eras, this evidence needs to be evaluated before a “dig” takes place. It has to be remembered that a ‘dig’ by its very nature destroys some evidence, so strict recording and slow progress are most important and has to be undertaken and supervised by qualified archaeologists using the best techniques at their disposal.

There is always the chance that more recent disturbances of the site, the laying of cables or pipelines can give false readings. Agricultural activities, ploughing and cultivation, site levelling or even building can cause disturbance and the accidental burying of metal objects can easily distort the readings of this sensitive equipment.

This site at North Hall certainly has archaeology beneath the surface. Whether it is the remains of our “Old North Hall Manor House Site”, remains to be seen. The impression by some archaeologists that have visited the site are very positive. There is an opinion that it may well date farther back than we originally thought. There could be Norman “Motte and Bailey” remains, surrounded by a moat complete with ponds etc.

The interpretation of the geophysical survey images will take a while. There may well be another type of equipment that could be used, we shall see. What is certain is that here is an interesting site, which has created a fascinating project, that has to be conscientiously continued with patience and enthusiasm.

We thank Penny for an interesting insight into modern archaeological investigations and the methods employed. We hope that we shall be able to continue to rely on assistance, support and encouragement from her and her colleagues as we maintain our research into this and the rest of “Widecombe Town Manor” and all that it could lead to for the Parish.

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