Learning one fact can cause you to observe differently. Tracy and I went to see a local lecture by Kevin Gardner on New England stone walls, where I asked how it is that those older walls were supposedly at least 4 feet high (if sheep can see the next field, they want to go there), but few seemed much more than two feet high now. Though there were clearly places where stones had been taken to be used for something else, these were near roads and structures. Deeper in the forest this seemed unlikely.
Mr. Gardner explained that I should look at both the tops and the bottoms of the wall. Most people do notice that stones have fallen to the ground from the top, though unevenly, but fail to notice the buildup of soil at the base of stone walls. Just as a snow fence causes snow to drift, any wall does this with soil, though much more slowly. Leaves especially get forced up against the granite, becoming soil in their time. This obscures or even buries some stones that have fallen, but even with intact structures can disguise where the real base of the wall originally was.
Sure enough, I see fallen stones that I missed before, and notice that the soil slopes up a bit on both sides of these walls, obscuring at least six inches and more commonly a foot of wall or more. I mentally scratch that away from the base and place the layabout stones back on top. They didn’t all fall to the same side, I remind myself (duh), so I add again the equivalent number of stones likely to be on the other side. (I do observe that far side at the end to check my work.) The effect is striking. The near view of whole landscapes can look different – and more like they did originally. The difference between 2-3 ft walls and 4-5 ft walls changes the whole perception of the space - for humans as well as sheep, apparently.