mentioned in favorite instruments ...
I'm shocked ...
I learned(when I was about 5 or 6), how the ground(that is ... the earth), was truly a ground ... electrically.
I had so much fun making electrical things work with 1-wire over hundreds of feet ... and additionally finding out that adding a diode to the long aerial line, along with the grounded line, that I could listen to music on the am radio to boot.
ANYWAY, I find it unreal that no one has ever considered(or maybe they have), that current tries to travel in the shortest, most conductive way possible.
I've always wonder if a person could take two 3' long rods, with only the bottom inch or so being "hot" and place it in the ground near where a "dense" stone might be found in otherwise, mush less dense soil, and in a pattern, use a second probe and measure differences in the conductivity between the two probes, looking for subtle differences in conduction.
A "stone finder", would be nice ... a simple, cost efficient "stone finder", would be nicer yet.
for us more un-attentive surveys ...
Wouldn't it be nice if there were NO CATEGORY, in the category box, which would actually force people, like me, to really address what the category is ... otherwise not allowing a posting without a chosen category?
I feign a mind disability, that I truly hope is a result of the heart ... liver ... blood-pressure ... mind-altering ... cholestral(sp), blood-thinning medicines I now take.
One day ... soon, I will stop spending 2 minutes to type these things, while spending 10 minutes trying to find the OBVIOUS mistakes, only to miss the OBVIOUS mistakes until I actually decide that I've spent too much time looking for OBVIOUS mistakes, that OBVIOUSLY don't exist, only to notice the OBVIOUS mistakes the minute I hit the POST button.
In our naturally rocky pasture areas it is a more critical challenge to identify THE STONE as opposed to simply finding a stone.
A local farmer friend of mine confessed to doing damage to a tillage implement several years in a row in a river bottom field. Finally, he was going slow enough and the tool struck the offending rock just right such that part of it stuck up above the surface. After several minutes of struggle, he managed to rip the offensive block of mineral from the soil, transport it to a convenient spot at the bottom of a gully, then continue working the ground, content in the knowledge that he would never damage his equipment again in that spot. A few years later he learned about how the early surveyors had set stones to mark section corners. Then he got that OH CRAP feeling as he realized why that stone had been where it was when there was no other rock of any kind for hundreds of feet in all directions.
Resistivity measurements are a standard tool for archaeology. I haven't used this technique personally, but have seen many maps generated by it. Here is a discussion and picture:
http://en.wikipedia.org/wiki/Electrical_resistance_survey
Another site with pictures:
targetgeophysics.com/geophysical...resistivity.html
You can't just take the resistance between a pair of probes, because you will be measuring the degree of contact as much as the resistance of the soil. You use a pair of probes connected to an electrical source to generate a known current in the ground, and another pair of probes between those to measure the induced voltage, which is proportional to soil resistance.
They seem to come with various numbers of probes, with a recorder to take the resistance between the probes. You stomp it to put the probes into the ground, record, pull it up, and advance a short distance. Somehow it is recording the distance advanced so they can plot the results. It appears to be a significant amount of physical work.
It would be a good technique for finding a stone IF the soil around there is reasonably uniform, the ground not too far from level, and the stone is the biggest anomaly in the immediate vicinity. I'm not sure of the depth range, but my impression is that it would be adequate for many survey corner stones.
