[click images to enlarge]
Walls like this are very common around Quincy and have maintained their integrity for over a century. The angled pieces on top certainly discourages any wall sitters. Most of the stone walls are not of the dry variety but have mortar holding them together like the second picture taken at the Fuller residence.
I like the granite markers used to mark the property line in the last picture. It's a great place to stack a few cords of wood . . . and from all predictions they'll be needing quite a few cords this winter.