Flocks of rocks
"Having slumped, scrambled, rolled, bounced, and walked, by turns, over this scraggy country, I arrived upon a side-hill, or rather side-mountain, where rocks, gray, silent rocks, were the flocks and herds that pastured, chewing a rocky cud at sunset. They looked at me with hard gray eyes, without a bleat or a low.''
-- Henry David Thoreau, in The Maine Woods