THE AMERICAN SWAN. 297 



the skin, and supporting the main part. It is of a 

 tough, horny material, and cylindrical in form, thus 

 combining strength and lightness; for in no form is a given 

 amount of matter so strong to support a weight or a strain 

 as in that of a tube or cylinder; and, of course, that is 

 also the form most favorable to levity. Next comes the 

 shaft supporting the vanes. This is somewhat four-sided, to 

 accommodate the vanes, and gradually diminishes toward 

 the extremity. It is usually bent, thus rendering the feather 

 much stronger and more convenient for its ordinary uses; 

 and it is also made more firm by a light pith. The flat 

 barbs, constituting the vane, join each other at their broad 

 sides, thus striking the air edgewise, and so opposing the 

 utmost resistance, just as a plank will sustain a greater 

 weight when set on edge than when lying flat. These barbs 

 are also broadest where they join the shaft, and taper to a 

 point at the outer edge of the vane. The broad sides of 

 these barbs are supplied with barbules, little hooks, so 

 arranged as to hook or latch into each other, and so form 

 the barbs of the vane into a continuous and firm sheet. At 

 the base of the vane is generally more or less down, accord- 

 ing to the nature of the bird, certain swimming birds, 

 such as Ducks and Geese, being noted for their down. 

 Some of the feathers of such species are down throughout, 

 and are called down-feathers; while all birds have more or 

 less feathers simply in the form of hairs. These last are 

 particularly troublesome in dressing the common fowl, and 

 are most conveniently cleaned by singeing. Again, the feath- 

 ers of certain birds have a peculiar style of structure. Those 

 of the Grebe are very open and loose, and of a glossy finish, 

 giving them somewhat the appearance of an elegant kind 

 of fur. "In the Owls the plumage is loose and soft; fila- 

 ments from the barbules extend upon the outer surface of 



