The Eider-duck, the soft downy feathers of which are so celebrated, and other sea fowls, are the most numerous of arctic birds.
(the soft downy feathers of which; are; so celebrated, and other sea fowls) (The Eider-duck; are; the most numerous of arctic birds)
the soft downy feathers of which The Eider-duck
are are
so celebrated, and other sea fowls
the most numerous of arctic birds