On Migration. 549 



spring ! Whether they rise to a great height and are carried 

 along by currents in the upper atmosphere, how they find their 

 way, and how they steer their course, for the most part so un- 

 erringly, are some of the many problems connected with migra- 

 tion upon which we are as yet but little informed. So im- 

 possible, indeed, did migration to distant lands seem to our older 

 writers on ornithology, including even the accurate Gilbert 

 White of Selborne, that they had recourse to the utterly unten- 

 able hypothesis that the Swallows and their compagnons de voyage 

 resorted to the reed-beds as autumn drew on, and hibernated at 

 the bottom of rivers ! not to revive and seek the upper air until 

 the entire winter had passed away and spring had returned ! A 

 wider experience and the observations of naturalists in other 

 countries have taught us whither our summer visitors betake 

 themselves, so that we can trace them on leaving our coasts to 

 the warm districts of North Africa, and see many of them pro- 

 longing their journey to the equator and even beyond it. More 

 and more marvellous, indeed, does this seem, when we recollect 

 the feeble flight of some diminutive Warbler, as it flits across one 

 of our meadows in Wiltshire from one hedge to another ; or the 

 laboured flapping of wings when some short-winged species 

 hurries off at its greatest speed, when suddenly alarmed. And 

 yet, by some means or other, when the season for migration 

 comes round, the diminutive and the feeble, the short-winged 

 and the heavy-bodied, generally collect into flocks or parties and 

 move off in a body, and in due course reach their destination. 

 Much of their journey ings necessarily takes place at night ; 

 but neither darkness, nor fogs, nor storms unless of unusual 

 violence nor wind, nor rain, nor anything else seems to baffle 

 them. On they go with unerring instinct, straight for the 

 point they desire to reach ; and generally, and within a very 

 few days of their usual appearance, they may be found in tlieir 

 old familiar haunts, as much at home as if they had never been 

 absent. How they know the direction, by what intuitive percep- 

 tion they steer their course so accurately, is another problem in 

 reference to migration which we cannot explain ; and this incom^ 



