circumstances compel us here to pass by this organic law, yet we are bound to refer to the chemical operations which commonly exhibit themselves in the tinting of feathers in a mode now sufficiently known to us.
659.
Plumage is of all colours, yet, on the whole, yellow deepening to red is commoner than blue.
660.
The operation of light on the feathers and their colours, is to be remarked in all cases. Thus, for example, the feathers on the breast of certain parrots, are strictly yellow; the scale-like anterior portion, which is acted on by the light, is deepened from yellow to red. The breast of such a bird appears bright-red, but if we blow into the feathers the yellow appears.
661.
The exposed portion of the