When I was a kid the sides of the road I lived on were gravel. I spent a lot of time looking at rocks as I went from one place to another in the neighborhood. Occasionally one of them would stand out from the rest. A different color or texture than most. I collected those special ones and kept them in a drawer in my bedroom. Now the gravel is gone, replaced with cement curbs up against the grass. My little collection is sitting in a box somewhere. The only remaining evidence of what was once a river of stones that flowed past my house.