Hovering (? Poising) of Birds

Abstract

LET me entreat the Duke of Argyll not to confuse the issue between us. I made bold to ask his Grace to draw a diagram showing by what balance of forces be thought a bird could be sustained in mid-air, motionless on motionless wings, in a perfectly horizontal wind; and he refers me to a beautiful drawing of a kestrel hovering, with fluttering wings, in still air. (See note at foot of page 161 of the “Reign of Law,” 5th edition, 1868: “Mr. Wolf's illustration of a kestrel hovering shows accurately the position of the bird when the action is performed in still air.”)