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will be able approximately to appreciate the feelings with which 
the naturalist travels from place to place ; wherever he may be he 
finds friendly forms. For years he has silently watched the 
interior economy and household arrangements of animated nature, 
‘and get he has not seen all; and on this account, he is never in 
want of employment. Every bird is a personal friend, the old ones 
he knows almost as well as he knows himself, and the new ones 
must be studied. How much more is there yet to observe! Rich 
as he may be in experiences, every fresh ramble brings him fresh 
mental treasure. The relations existing between him and the 
bird become each day more and more intimate ; he knows the lives 
and habits of each; when each arrives or takes its departure ; 
where is its abode; how it is made; when it is occupied by a 
happy troop of nestlings; when deserted. The naturalist knows 
his friends by their notes, flight and bearing. Every new bird 
raises his spirits a step higher; every fresh discovery is a step 
onward in the knowledge of the ways and means ofall things. He 
is indebted to his friends for many a happy hour ; their lives are a 
pattern worthy of imitation.” 
Here then we may ask—What is a bird? How can a bird be nown 
from all other vertebrate animals ? The chief character which distin- 
guishes the class of birds is undoubtedly the clothing of the body with 
feathers. Other characters they also possess but not exclusively. 
For instance they have the power of flight developed in the highest 
degree ; but there are some birds, such as the Apteryx, the Ostrich 
and the Cassowary which cannot fly at all; while on the other hand, 
there are flying mammals, such as Bats, and in a less degree Flying 
Squirrels, and there are reptiles, which can progress through the air 
by means of flight. Again, birds lay eggs from which they produce their 
young, but so do many reptiles and fish,so that this cannot be considered 
a prerogative of the class of birds. Their Dil] is hard and sheathed 
in horn, but so is that of the Duck-billed Platypus a mammal, and 
Turtles also have beaks. Most but not all birds build nests, and in 
this they stand almost alone among the higher animals, but still 
nest-building propensities are developed in many of the Mam- 
malia, in the Lemurs and Mice, for instance—while some fish also 
build wonderful nests. But all birds. whether they fly or not, are 
clothed with feathers, and this distinguishes the class Aves in the 
existing state of nature. The majority are specially adapted for 
flight, and as this is undoubtedly the most vigorous form of locos 
motion, the greatest muscular efforts being required to raise and 
sustain a body above the ground and to propel it rapidly through 
the air, a large development of muscular energy is necessary. The 
great strain on the circulation of the blood is met by a heart, not 
only as complete-as in the Mammals, but with stronger mechanism 
