Rensselaer Semi-Weekly Republican, Volume 37, Number 6, Rensselaer, Jasper County, 20 January 1905 — FEATHERS ARE AIR ENGINES [ARTICLE]

FEATHERS ARE AIR ENGINES

How Birds Weighted with Prey Remain Motionless in Air for Honrs. The soaring flight of birds, like the condor and frigate bird, which remain suspended in the air for hours, even when weighted with prey, and without a single movement of their outstretched wings, has hitherto been unexplained. J. Lancaster, who has devoted fifteen years to finding an explanation for this apparent violation of physical law, making experiments from a cliff 1,000 feet high in Colorado, where yellow-tailed hawks are numerous, found that after a forest fire soot was found on a hawk’s quill between the spicules. This deposit showed the direction of air currents through the wing. Writing of his discovery in the London Engineer, he says: “What is a feather? It is an air engine and tlie bird surfaces are made of them. They have been looked on ns a light, flexible material for making an extended surface impervious to air, that would readily fold upon itself, and their exquisite mechanical structure has been overlooked. They consist of a quill arul two vanes made of spicules, between which are the plates. The plats cross a channel about one-forti-eth of an inch wide, made by the spicules. There are about 1,000 of them to the inch, being practically innumerable, and they are located at the outer surface, filling about one-fifth part of the depth of the channel. They areabout tbe twenty-thousandth part of an inch thick, as nearly as an amateur with the microscope could deetnhine, so that nineteen-twentieths of the space of the channels is open to the passage of air. They are beautifully curved at their outer edges. The mechanical service of the plates is obvious. The curve impinges against the air current through the feathers and drives the bird to the front. Pressure produced by the normal factor of weight is thus made to serve as the motive power of flight.”