DOWN, the fine feathers on the breasts of several birds, particularly of the duck kind. That of the eider duck is the most valuable. These birds pluck the down from their breasts and line their nests with it. Three pounds of this down may be compressed into a size scarcely larger than one's fist; yet it is afterwards so dilatate as to fill a quilt five feet square. That found in the nests, and termed live down, is most valued; being much more elastic than that plucked from the dead bird.