in Thoreau’s Journal

I go along below the north end of the Cliffs. The rocks in the usual place are buttressed with icy columns, for water in almost imperceptible quantity is trickling down the rocks. It is interesting to see how the dry black or ash-colored umbilicaria, which get a little moisture when the snow melts and trickles down along a seam or shallow channel of the rock, become relaxed and turn olive-green and enjoy their spring, while a few inches on each side of this gutter or depression in the face of the rock they are dry and crisp as ever. Perhaps the greater part of this puny rill is drunk up by the herbage on its brink.