Thoreau writes in his journal:
Spermophilus eating oats in horse-dung. See a scum on the smooth surface of the lake 3 or 4 feet from shore, the color of the sand of the shore, like pollen & lint, which I took it to be. Taking some up in my hand, I was surprised to find it the sand of the shore, sometimes pretty large grains 1/10 inch diameter—but most 1/20 or less. Some dark brown, some white or yellowish. Some minute but perfectly regular oval pebbles of white quartz. I suppose that the water rises gently, lifts up a layer of sand where it is slightly cemented by some glutinous matter, for I felt a slight stickiness on my hand after the (gravel or) sand was shaken off.
(Thoreau’s Minnesota Journey, 18)
