158 THE IMPORTANCE OF BIRD LIFE 



tions in the surface of the feather. The varia- 

 tions consist. of minute furrows and ridges so ar- 

 ranged as to reflect light and thus alter the true 

 tint of the feather. Purples and blues fall within 

 this class, and generally green, though seldom yel- 

 low. By eradicating these physical irregularities 

 through soaking in water, the basic color is 

 brought out ; but the feather will regain its abnor- 

 mal hue when dried. 



The third type is found in the iridescent metal- 

 lic tints. These beautiful shades are entirely 

 dependent upon the structure of the feather, and 

 pigment, save as a mirror for reflecting light, is 

 in no way concerned. In humming-birds, pea- 

 cocks, and starlings, — ^birds whose feathers appear 

 bright but basically are not, — the body feathers 

 are covered with tiny ridges, knobs, pits, and ex- 

 crescences, which tend to dissolve light into its 

 component parts. Added to these are reflecting 

 pigmented plates so arranged as to give forth only 

 prismatic rays. The entire combination thus 

 gives to the birds those delicate sheens so peculiar 

 and beautiful. 



2 



The Rise of Ornamental Plvimes 



Ever since man first became a thinking being 

 he has fought a victorious battle with wild and 

 savage beasts. Because of his superior cunning 



