C *7« 1 



The obvious anfwer to this is, that no welhattefted inftances 

 can be produced of fuch a migration, as I fhall endeavour to mew 

 hereafter ; but, befides this convincing negative proof, there are 

 not others wanting. 



They who fend birds periodically acrofs the fea, being preffed 

 with the very obvious anfwer I have before fuggefted, have re- 

 courfe to two fuppofitions, by which they would account for their 

 not being obferved by feamen during their paflage. 



The firft is, that they rife fo high in the air that they become 

 invifible 0 ; but unfortunately the fifing to this extraordinary 

 height, or the falling from it, is equally deftitute of any ocular 

 proof, as the birds being feen whilft crofting an ocean. 



I have indeed converfed with fome people, who conceive they 

 have loft fight of birds by their perpendicular flight ; I mull: 

 own, however, that I have always fuppofed them to be fhort- 

 fighted, as I never loft the fight of a bird myfelf, but from its 

 horizontal diftance, and I doubt much whether any bird was ever 

 feen to rife to a greater height than perhaps twice that of St. Paul's 

 crofs d . 



There 



c It is well known that fome ornithologies have even fuppofed that 

 they leave our atmofphere for that of the moon. SeeHarl. Mifcell.vol.il. 



p. 561. 



A bird of paffage, loft as foon as found ; 

 Now in the moon perhaps, now under ground. 



Pope. 



d Wild-geefe fly at the greater! height of any bird I ever happened to 

 ,attend to ; and from comparing them with rooks, which I have fre- 

 quently looked at, when perched on the crofs of St. Paul's, I cannot 

 think that a wild-goofe was ever diminifhed, to my fight at leaft, more 

 than he would be at twice the height of St. Paul's, or perhaps 300 yards. 

 Mr. Hunter, F. R. S. informs me, that the bird which hath appeared to 

 him as the higheft flier, is a fmall eagle on the confines of Spain and 

 Portugal, which frequents high rocks. He hath firft feen this 



fpecies 



