THE ANIMAL KINGDOM. 305 



ments and knotty calculations that the sailor trusts himself 

 upon the sea ; whereas our winged travellers, without guide 

 or compass, and without ever losing their way, transport 

 themselves from the polar circle to the tropical regions. 

 The cranes pass the summer on the stormy strands of Scan- 

 dinavia, and the winter amid the ruins of the palaces of the 

 Pharaohs. 



The mechanism of birds is admirably suited to aid their 

 rapid flight. Their aerial oars, moved by muscles of ex- 

 traordinary power, easily adapt themselves to all the haz- 

 ards of their flight through the elevated regions of air. 

 There are birds, as the swallow, for instance, to which flight 

 is so easy that they seem to make a sport of it. A passive 

 force further assists their suspension in the plains of the at- 

 mosphere ; air, rarefied by the warmth of the body, pene- 

 trates into all its cavities, and even to the interior of the 

 bones. Rendered thus specifically lighter, like Montgolfier 

 balloons filled with warm gas, they float without effort amid 

 the clouds. Such is the daring flight of the condors which 

 launch themselves from the frozen summits of the Andes 

 towards the sky, and soon disappear from sight, without 

 one's being able to explain how they can breathe so rarefied 

 an atmosphere. 



The bird, though endowed with such a slight frame, nev- 

 ertheless surpasses in strength the ponderous engines which 

 glide along our railroads. Its vessels and fibres, notwith- 

 standing their wonderful delicacy, work and resist more 

 energetically than our heavy wheel-work and cast-iron 

 tubes ; in the one is seen the finger of God, in the other 

 only the genius of man ! Launched like an arrow into space, 



