BIRDS IN GENERAL. 41 



trees, or even sink into the deepest lakes, and find security for the 

 winter season by remaining there in clusters at the bottom. However 

 this latter circumstance may be, their retreat into old walls is too well 

 authenticated to remain a doubt at present. The difficulty, therefore, 

 is to account for this diffeience in these animals thus variously prepa- 

 ring to encounter the winter. It was supposed that in some of them 

 the blood might lose its motion by the cold, and that thus they were 

 rendered torpid by the severity of the season ; but Mr. Buffon having 

 placed many of this tribe in an ice-house, found that the same cold by 

 which their blood was congealed was fatal to the animal ; it remains, 

 therefore, a doubt to this hour, whether there may not be a species of 

 swallows to all external appearance like the rest, but differently formed 

 within, so as to fit them for a state of insensibility during the winter 

 here. It was suggested, indeed, that the swallows found thus torpid, 

 were such only as were too weak to undertake the migration, or were 

 hatched too late to join the general convoy ; but it was upon these 

 that Mr. Buffon tried his experiment ; it was these that died under 

 the operation. 



Thus there are some birds which, by migrating, make a habitation 

 of every part of the earth ; but in general every climate has birds 

 peculiar to itself. The feathered inhabitants of the temperate zone 

 are but little remarkable for the beauty of their plumage ; but then 

 the smaller kinds make up for this defect by the melody of their voices. 

 The birds of the torrid zone are very bright and vivid in their colours ; 

 but they have screaming voices, or are totally silent. The frigid zone, 

 on the other hand, where the seas abound with fish, are stocked with 

 birds of the aquatic kind, in much greater plenty than in Europe ; and 

 these are generally clothed with a warmer coat of feathers ; or they 

 have large quantities of fat lying underneath the skin, which serves to 

 defend them from the rigours of the climate. 



In all countries, however, birds are a more long-lived class of ani- 

 mals than the quadrupeds or insects of the same climate. The life 

 of man himself is but short, when compared to what some of them en- 

 joy. It is^ said that swans have been known to live three hundred 

 years ; geese are often seen tft live fourscore ; while linnets and other 

 little birds, though imprisoned in cages, are often found to reach four 

 teen or fifteen. How birds, whose age of perfection is much mor 

 early than that of quadrupeds, should yet live comparatively so much 

 longer, is not easily to be accounted for : perhaps, as their bones are 

 slighter, and more porous, than those of quadrupeds, there are fewer 

 obstructions in the animal machine ; and nature, thus finding moro 

 room for the operations of life, is carried on to a greater extent. 



All birds in general are less than quadrupeds ; that is, the greatest 

 of one class far surpasses the greatest of the other in magnitude. The 

 ostrich, which is the greatest of birds, bears no proportion to the ele- 

 phant ; and the smallest humming-bird, which is the least of the class, 

 is still far more minute than the mouse. In these the extremities of 

 nature are plainly discernible ; and in forming them she appears to 

 have been doubtful in her operations : the ostrich, seemingly covered 

 with hair, and incapable of flight, making near approaches to the quad 



VOL. Ill D 



