[ 2 6 7 ] 



fwallows, to enter into a very minute difcuiTiors of 

 what may, or may not, be inferred from his obfer- 

 vation according to his own narrative. 



I mall firft however confide-r the general argu* 

 ments, from which it is fuppofed that birds of paflage 

 periodically traverfe oceans, which indeed may be 

 almolt reduced to this fingle one, viz. we fee certain, 

 birds in particular Jeafons, and afterwards we fee 

 them not ; from which data it is at once inferred, 

 that the caufe of their disappearance is, that they 

 -have croffed large tracts of fea, 



The obvious anfwer to this is, that no well-attefted 

 inflances can be produced of fuch a migration, as I 

 ihali endeavour to mew hereafter j but befides this 

 convincing negative proof, there are not others want* 



ing \ 



Thofe who fend birds periodically acrofs the' -fea, 



being prefTed with the very obvious anfwer I have 



"before fuggeiled, have recourfe to two fuppofitions, 



"by which they would account for their not being 



obferved by feamen during their paflage. 



The flrft is, that they rife fo high in the air that 

 they become invifible * j but unfortunately the riling 

 to this extraordinary height, or the falling from it, is 

 equally deftitute of any ocular proof, as the birds 

 being feen during their paflage. 



I have indeed converfed with fome people, who 

 conceive they have loft fight of birds by their per* 

 pendicular flight -, I mull: own, however, that I have 



** It is well known that fome ornithologifts have even fup- 

 pofed that they leave our atmofphe'ie for that of the ;Mo©n. Sec 

 HarU Mifc. Vol. II. p. 561. 



Mm a always 



