The vast and little-known island of Papua contains some specimens of the feathered race of surpassing glory. The _Epimachi_, or Plume-birds, take a prominent place in this category. They are remarkable for the erectile scale-like feathers of the sides and shoulders, which form large fan-shaped tufts, standing out from the body in a very striking manner. Speaking of the superb Epimachus, Sonnerat, its describer, thus writes:--"As if to add to the singularity of this bird, nature has placed above and below its wings feathers of an extraordinary form, and such as one does not see in other birds; she seems, moreover, to have pleased herself in painting this being, already so singular, with her most brilliant colours. The head, the neck, and the belly are glittering green; the feathers which cover these parts possess the lustre and softness of velvet to the eye and touch; the back is changeable violet; the wings are of the same colour, and appear, according to the lights in which they are held, blue, violet, or deep black; always, however, imitating velvet. The tail is composed of twelve feathers, the two middle feathers are the longest, and the lateral feathers gradually diminish; it is violet, or changeable blue above, and black beneath. The feathers which compose it are as wide in proportion as they are long, and shine above and below with the brilliancy of polished metal. "Above the wings the scapularies are very long and singularly formed; their points being very short on one side, and very long on the other. These feathers are of the colour of polished steel, changing into blue, terminated by a large spot of brilliant green, and forming a species of tuft or appendage at the margin of the wings. "Below the wings spring long curved feathers, directed upwards; these are black on the inside, and brilliant green on the outside. The bill and feet are black."[206] The same author, in referring to the brilliant metallic hues of this and other birds, takes occasion to notice the iridescent effect which is produced by the different angle at which light falls on the feathers. The emerald-green, for instance, will often fling out rays of its two constituent primary colours, at one time being blue-green, at another gold-green, while in certain lights all colour vanishes, and a velvet-black is presented to the eye. The ruby feathers of several birds become orange under certain lights, and darken to a crimson-black at other times. [Illustration: MOURNING THE DEAD CUCKOO.] This change of hue is analogous to the well-known iridescent changeableness of the nacre which lines various shells, and is owing to the structure of its surface reflecting the light in different rays, according to the angle at which it falls upon the feathers.