For the most part the soils and underlying geology are very free draining which in the height of summer are unlikely to contain much residual moisture. The buried archaeological features which were the focus of attention consisted primarily of stub walls of local derived stone, which appear to have been laid onto the ground without the presence of additional foundations (foundation trenches). Foundation trenches can often act as conduits for water attracting and retaining moisture at the expense of the surrounding matrix. The walls themselves, however, will often dry out more rapidly leaving a moisture imbalance between the wall and is foundation trench. With the absence of a foundation trench, and in very dry conditions the moisture balance between the wall and its surrounding matrix is likely to be in equilibrium. This in effect means that the variable resistance to an electrical current passed between the two mediums will be undetectable as long as the ground conditions remain unchanged. Of course it is largely a matter of speculation as to whether conditions for resistivity would improve under more favorable moist conditions in the autumn, but the experience of the author working in Britain would suggest that it would.
The magnetometer survey has had a greater degree of success particularly in the detection of industrial activity. The identification of what are almost certainly kilns has enabled specific targeting of areas for excavation which has proved to be both reliable and accurate (Wilson pers.. comm). The use of magnetometry for the detection of walls is very rarely successful and depends on the walling material having a measurable magnetic density which is at variance with the surrounding soil matrix. At Campanaio this does not appear to be the case which has resulted in a negative response to wall/structure identification. This could be confirmed by sampling and laboratory processing of samples but the sensitivity of the gradiometer is usually a sensitive enough device to obviate this need.
In conclusion although the aims and objectives of the project were
only partially met, the survey has demonstrated the potential of the techniques
and also has provided some valuable data on which to make a basis for recommendations
on the future application of geophysical techniques on similar sites in
a similar landscape/environment.
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John Gale (email: firstname.lastname@example.org)