BIRDS IN GENERAL. 29 



days and nights to cover the surface of the river 

 Calix. 



This migration from the north usually begins 

 in September, when they quit their retreats, and 

 disperse themselves over all the southern parts 

 of Europe. It is not unpleasing to observe the 

 order of their flight ; they generally range them- 

 selves in a long line, or they sometimes make 

 their march angularly, two lines uniting in the 

 centre like the letter V reversed. The bird 

 which leads at the point seems to cleave the air, 

 to facilitate the passage for those which are to 

 follow. When fatigued with this laborious sta- 

 tion, it falls back into one of the wings of the 

 file, while another takes its place. With us they 

 make their appearance about the beginning of 

 October, circulate first round our shores, and 

 when compelled by severe frost, betake them- 

 selves to our lakes and rivers. Some, indeed, 

 of the web-footed fowl, of hardier constitutions 

 than the rest, abide the rigours of their northern 

 climate the whole winter; but when the cold 

 reigns there with more than usual severity, they 

 are obliged to seek for more southern skies : 

 they then repair with the rest for shelter to 

 these kingdoms ; so that the diver, the wild 

 swan, and the swallow-tailed sheldrake, visit our 

 coasts but seldom, and that only when compelled 

 by the severity of their winters at home. 



It has been often a subject of astonishment, 

 how animals to all appearance so dull and irra- 

 tional should perform such long journeys ; should 

 know whither to steer, and when to set out upon 



