BIRDS 103 



to rise rapidly without any exertion ; and they can 

 also easily fly with the wind. 



We see, therefore, that the bird is enormously 

 assisted in flying by the nature of its organism. We 

 may now inquire whether the statements made with 

 regard to the altitude it reaches are supported by 

 observation. 



When we follow the flight of birds of prey they 

 seem to rise to immeasurable heights, and even the 

 lark often passes beyond our vision into the blue 

 sky. But it would be premature to draw any inferences 

 from this, as we do not know how far we may not 

 be subject to illusion by dazzling. The results of 

 balloon observations are more important. In these 

 an eagle was once seen at a height of 3,300 yards and 

 a lark at a height of 1,500 yards; but there were so 

 few birds at this height that we must conclude they 

 rarely rise above 1,100 yards. It was also noticed 

 that a pigeon, which was dropped from a balloon at 

 a great height, first fell downwards, and only found 

 sufficient resistance for its wings to use properly in 

 thicker strata of the atmosphere. 



However, these facts gives us no information as 

 to the altitude of the migration-flight, and unfortunately 

 we have not very many observations on this. Gatke 

 was one of the few who have seen swarms of migratory 

 birds go past, and he gives a superb description of 

 one night in October in which this wonderful picture 

 unrolled before him. It was a dark, starless night, 

 only lit by the rays of the light-house which seemed 

 to reach out endlessly into the night. The darkness, 



