174 THE STORY OF THE BIRDS 



miles ; Cranes have been detected passing across 

 the sun's disc at an estimated altitude of five and 

 three-quarter miles ! These latter birds, we may 

 mention, have been observed crossing the vast 

 Central Asian mountains at great elevations 

 above them. The most important benefit de- 

 rived from such a lofty course is the increased 

 range of vision that it ensures. The higher a 

 bird flies the farther it can see, the more ex- 

 tended becomes the visible segment of the earth's 

 sphere below it. From such lofty courses the 

 earth and sea spread out like a vast panorama 

 below the migrating bird, charged with a full 

 knowledge of the topography of its accustomed 

 route ; all the old familiar landmarks are recog- 

 nised as the wondrous journey is performed. 



But all this is the brighter aspect of the 

 migration flight. Very often fogs and rain mists 

 obscure the land, and storms overtake these 

 feathered pilgrims, bringing disaster and death. 

 At such times during spring and autumn (the 

 latter season more especially, because then the 

 migrants are more numerous) scenes of rare 

 wonder are often witnessed at the lighthouses 

 and light-vessels on coasts frequented by migrant 

 birds. The poor lost little pilgrims are attracted 

 to the lanterns very often in tens of thousands, 



