There is nothing like those old builders left. Well, just one or two. The bulk of my year's work is a wall which runs impossibly down the side of a hill - four years it'll take me, at least. It wasn't that the neighbours were hateful per se. it was just the prospect of keeping the herds from being entangled perhaps.

The carved gear-shapes in the tops of the stones appear regardless of rock type. Just as often in soft sandstone (the Man eg) as in Millstone Grit (Devil's Arrow). The grooves only give thw stone the description 'polissoir' when they've fallen over. A geologist would be the qualified person to ask an opinion of.