[ 266 ] 
Calais, from Gibraltar to Tangier, or any other fuch 
narrow ftrait, as the oppolite coafts are clearly within 
the bird’s ken, and the pafiage is no more adventurous 
than acrofs a large frefh wateriake. 
I as little mean to deny that there may be a peri- 
odical flitting of certain- birds from one part of a con- 
tinent to another : the Royfton Crow, and Rock 
Ouzel, furnifh inftances of fuch a regular mi- 
gration. 
What i mean chiefly to contend therefore is, that 
it feems to be highly improbable, birds fhould, at 
certain feafons, traverfe large tradts of fea, or rather 
ocean, without leaving any of the Jame fpecies be- 
hind, but the fick or wounded. 
As this litigated point can only receive a fatisfadtory 
decifion from very accurate obfervations, all preceding 
naturaliffs, from Ariftotle to Ray, have fpoken with 
much doubt concerning it. 
Soon after the appearance of Monf. AdanfonV 
voyage to Senegal, however, Mr. Collinfon firft, in 
the Philofophical Tranfadlions and after him the 
mofl eminent ornithologies of Europe, leem to 
have confidered this traveller’s having caught four 
European Swallows on the 6th of Odtober, not 
far from the African coaft, as a decifive proof, 
that the common fwallows, when they difappear 
in Europe, make for Africa during the winter, and 
return again to us in the fpring. 
It is therefore highly incumbent upon me, who 
profefs that I am by no means fatished with the ac- 
count, given by Monf. Adanfon of thefe European 
* Part II. 1760, p. 459, & feq. 
fwallows# 
