300 ON THE COLOURS OF THE FEATHERS OF BIRDS. 



It may here be proper to examine these feathers, and to search for the 

 cause of their brilliancy. To do this successfully we should compare 

 them with the feathers of different kinds of birds. 



The colours which usually adorn birds may be divided into several 

 classes : they are dull or brilliant, changeable or metallic. 



The dull colours are those which are not susceptible of change from 

 the different directions of the rays of light : the plumelets of the 

 feathers which are thus coloured have the quill furnished on each side 

 from the base to the extremity with very fine and slender loose beards. 

 (Page 305, fig. 1.) These colours predominate most in the birds of 

 our own country, 



Brilliant colours are those which, without having the property of 

 changing their shades, possess nevertheless a brilliancy similar to that 

 of polished bodies. This brightness is owing to the peculiar form of 

 the beards. A great number of birds have very brilliant colours ; such 

 as the red feathers of the woodpeckers, the yellow and red feathers 

 of the cassiques, those of the manakins, guit-guits, &c. The beards of 

 these feathers (fig. 2) have only fringes at their base, the rest is bare, 

 cylindrical, smooth and highly polished ; but this cylindrical form 

 is not complete ; when seen from beneath, these beards are hollowed 

 longitudinally in channels (thus [o] ), which represents a section of 

 one of these beards. This smooth part is a continuation of the quill, 

 and differs from it only in being double the thickness, as if the 

 quantity of matter which composes the fringes were here reunited to 

 increase the bulk of the quill. This supposition is not altogether 

 without foundation. If we examine one of the feathers taken from the 

 head of our own king-fisher, or the little tufted king-fisher of Africa, 

 we shall find that this feather, which is black from the base to the 

 extremity, is varied by a spot of very brilliant light blue ; and it may 

 be remarked that the quills of each beard (fig. 3) are furnished with 

 fringes at the base and extremity, while the middle part is thicker, 

 cylindrical and destitute of beards, or at least they are so small, as to 

 be perceptible only by the aid of a strong magnifying glass. 



We find the beards of brilliant feathers furnished also with fringes ; 

 but the latter are very short. The European jay has feathers in the 

 wings of a very lively blue ; the beards of these feathers (fig. 4) have 

 a long quill stalk which is thick, very shining, and coloured alternately 

 white, blue, and black ; this quill is furnished throughout with fringes ; 

 but they are short and black, and are only perceptible when the beard 

 is separated from those that are near it. It is the same with the blue 



