Sect, XVI. 12. 3. OF INSTINCT. 127 



fowl, which are very numerous, all difappear, and are fuppofed 

 to fly to warmer climates, except the rail, which, from its inabil- 

 ity for long flights, probably fleeps, like our bat, in their winter. 

 The following account from the Journey of Profeflbr Gmelin, 

 may entertain the reader. " In the neighbourhood of Krafnoi- 

 ark, amongft many other emigrant water fowls we obferved a 

 great number of rails, which when purfued never took flight, 

 but endeavoured to efcape by running. We inquired how thefe 

 birds, that could not fly, could retire into other countries in the 

 winter, and were told, both by the Tartars and AfTanians, that 

 they well knew thofe birds could not alone pafs into other coun- 

 tries: but when the cranes (les grues) retire in autumn, each one 

 takes a rail (un rale) upon his back, and carries him to a warmer 

 climate." 



Recapitulation, 



1. All birds of paffage can exift in the climates, where they 

 are produced. 



2. They are fubje<fr. in their migrations to the fame accidents 

 and difficulties, that mankind are fubjetl: to in navigation. 



3. The fame fpecies of birds migrate from fome countries, 

 and are refident in others. 



From all thefe circumftances it appears that the migrations of 

 birds are not produced by a necefiary inftindt, but are acciden- 

 tal improvements, like the arts among mankind, taught by their 

 contemporaries, or delivered by tradition from one generation 

 of them to another. 



XIII. In that feafon of the year which fupplies the nourifh- 

 ment proper for the expe&ed brood, the birds enter into a con- 

 tract of marriage, and with joint labour conftruct a bed for the 

 reception of their offspring. Their choice of the proper feafon, 

 their contracts of marriage, and the regularity with which they 

 conftruft their nefts, have in all ages excited the admiration of 

 naturalifts ; and have always been attributed to the power of in- 

 ftinc"t, which, like the occult qualities of the ancient philofo-- 

 phers, prevented all further inquiry. We fhall confider them 

 in their order. 



'Their Choice of the feafon. 



Our domeftic birds, that are plentifully fupplied throughout 



the year with their adapted food, and are covered with houfes 



from the inclemency of the weather, lay their eggs at any fea* 



fon : which evinces that the fpring of the year is not pointed 



out to them by a neceilarv inftinct 



Whilft 



