76 
ON THE CLASSIFICATION OF BIHDS. 
been copied and recopied in the volumes of others ; hut, 
on the other hand, they may hope to see many of those 
subjects placed in a new light, accompanied by some 
original information, which peculiar circumstances have 
placed us in the way of acquiring. But to proceed : — 
We shall only take a hasty glance at the construction of 
feathers in general, and then proceed to notice those 
particular modifications of their form which influence 
their natural habits, and indicate their natural affinities. 
(70.) The FEATiiEns which are upon a bird are of three 
different kinds : 1. Those which are next to the body, 
and are altogether concealed from the sight ; 2. Those 
which are external, but are used in flight ; 3. Those 
by which the body is sustained in the air. The sub- 
stance wliich composes the first is known by the name 
of down. It is more analogous to the soft fur of qua- 
drupeds than to the feathers, properly so called, of 
birds, inasmuch as it does not possess that distinctness of 
parts which is observable in a perfect feather. Some 
of its obvious uses are to keep the body in an equal de- 
gree of temperature, and to resist cold or wet, so that it 
jierforms the same office as an under-vestment of flannel 
does to the human skin. This inner covering, however, 
is not to be found in all birds; or, at least, it is so slight 
in some that its presence is only indicated by soft hairs 
thinly scattered over the body, as we see in domestic 
fowls and other poultry. It may be observed, however 
that in such birds which have not, like the ducks, a dis- 
tinct layer of down, the lower part of the external feathers 
supphes the deficiency, so that it may be said the down 
is only removed to another situation, and instead of lieing 
detached, it is placed at the base of the true feathers 
where it equally covers and protects the skin. Down, 
when existing as a separate substance, is mostly confined 
to the bodies of aquatic birds, for the manifest intention 
of additional warmth, and to render the skin still more 
inaccessible to the watery element ; this delicate sort of 
feathers, as is well known, is most developed in the 
duck family, particularly on the eiders and swans. It is 
