degree of mortification, when I reflected that, after 

 all our pains and inquiries, we are yet not quite cer- 



tain to what regions they do migrate ; and are still 

 farther embarrassed to find that some do not actu- 

 ally migrate at all. 



These reflections made so strong an impression 

 on my imagination, that they became productive of 

 a composition that may perhaps amuse you for a 

 quarter of an hour when next I have the honour 

 of writing to you. 



Selborne, February 28, 1769. 



93 



