20 HISTORY OK 



afiford them every opportunity of collecting so minute a food, 

 which is probably, of all others, tlie most grateful. We are not 

 to be astonished, therefore, at the amazing numbers of fowl that 

 descend from these regions at the approach of winter ; numbers 

 to which the army of Xerxes was but trilling in comparison ; and 

 which Linnaeus has observed for eight whole 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 themselves in a long 

 line, or they sometimes make their mark 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 pas. 

 sage for those which are to follow. When fatigued with this 

 laborious station, it falls back into one of the wings of the file, 

 while another takes its place. With us they make their appear- 

 ance about the beginning of October, circulate first round our 

 shores, and, when compelled by severe frost, betake themselves 

 to our lakes and rivers. Some, indeed, of the web-footed fowl, 

 of hardier constitutions than the rest, abide the rigour 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 often been a subject of astonishment, how animals to 

 all appeai-ance so dull and irrational should perform such long 

 ioumeys, should know whither to steer, and when to set out upon 

 such a great undertaking. It is probable that the same instinct 

 which governs all their other actions operates also here. They 

 rather follow the weather than the country ; they steer only from 

 colder or warmer climates into those of an opposite nature ; and 

 finding the variations of the air as they proceed in their favour, 

 go on till they find land to repose on. It cannot be supposed 

 that they have any memory of the country where they might have 

 spent a former winter ; it cannot be supposed that they see the 

 country to which they travel, from their height in the air ; since, 

 though they mounted for miles, the convexity of the globe would 



