OF NATURAL HISTORY. 473 



CHAPTER XX. 



Of the Migration cf Animalu 



TH E Hon. Dalnes Barrlngton, in his EJJay on the Periodical 

 Appearing and Difappearing of certain Birds ^ at different times 

 of the year *, has, by many ingenious arguments, as well as curious 

 fadts, rendered it extremely probable, that no birds, however ftrong 

 and fwift in their flight, can poffibly fly over fuch large trads of 

 the ocean as has been commonly fuppoied. He admits partial mi- 

 grations ot fittings, as he calls them, though he does not attempt to 

 afcertain the diftances of thefe flittlngs. With regard to the fwal- 

 lows, of which there are feveral fpecies in Britain, fome naturalifts, 

 of whom the Hon. Daines Harrington is one, are inclined to think 

 that they do not leave this ifland at the end of autumn, but that they 

 lie in a torpid ftate till the beginning of fummer in the banks of 

 rivers, the hollows of decayed trees, the recefles of old buildings, 

 the holes of fand-banks, and in fimilar fituations. That fwallows, 

 in the winter months, have fometimes, though very rarely, been 

 found in a torpid ftate, is unqueftionably true. Neither is the infe- 

 rence, that, if any of them can furvive the winter in that ftate, the 

 whole of them may fubfift, during the cold feafon, in the fame con- 



3 O t dltton, 



* Phil. Tranfaft. vol 62. pag. 265, &c. 



