INTRODUCTORY CHAPTER. 1 "7 



their migrations, and in what manner to direct their course, it 

 may with great propriety be answered, that the same all-ruling 

 Power which bestowed reason on us has given instinct to them : 

 the change in the atmosphere may indicate the proper time of 

 removal ; and it is also to be observed, that their course is de- 

 termined rather by the weather, than the situation of countries; 

 and that they remove from a colder to a warmer climate, or the 

 reverse, as the state of the air and their own feelings give the 

 impulse and direction. 



The migrations of the swallow and the cuckoo have been 

 particularly noticed by every writer on ornithology ; and various 

 opinions have been formed respecting their disappearance, and 

 the state in which they subsist during that interval. Some 

 naturalists have imagined that these birds do not migrate at the 

 end of autumn, but that they lie in a torpid state, concealed in 

 banks, in the hollows of decayed trees, among the ruins ~f f-!d 

 buildings, and other sequestered places, until the return of -■ .:. 

 mer. Some have, upon vague information, asserted that they 

 cling together by the feet, and thus great numbers being con- 

 glomerated in a mass, they sink themselves to the bottoms of 

 rivers or pools, where they lie concealed under the water. It 

 requires, however, no great depth of reasoning to prove the 

 physical impossibility of this hypothesis. On the one hand, it L< 

 certain that swallows have been found in winter in a torpid 

 state; but these instances seldom occur, and consequently will 

 not support the inference, that if any individuals survive the winter 

 in that state, the whole species is preserved in the same manner. 

 Several instances of cuckoos having been found in a similar state, 

 might be adduced; as well as of swallows, house-martins, &c. 

 having been seen flying about, long after the general migration 

 had taken place; all which circumstances leave no room to 

 doubt that several young birds which have been late hatched, 

 not finding themselves strong enough to undertake a long voyage, 

 remain behind, and lie concealed in hiding-places until the return 

 of spring, and that the cold of winter benumbs and renders them 

 torpid. On the other hand, the actual migration of the swallow 

 tribe has been proved by a number of well-authenticated facts, 

 taken from the observations of navigators, who have been eye 

 witnesses of their flights, and who inform us that the rigging of 

 their ships has often been covered with the weary travellers 

 These accounts, indeed, we find so frequently occurring in the 

 narratives of voyages, that we cannot doubt of their authenticity, 

 nor of the reality of these migrations. However, after all the 

 inquiries of naturalists into this mysterious branch of animal 

 economy, the subject remains involved in no small degree of ob- 

 ticuritv ; and after all our researches, we are not vet certain into 

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