BIRDS. 295 



them. This is no sliglit undertaking, as tlieir llight is directed 

 to Congo, Senegal, and along the whole Morocco shore. There 

 are some, however, left behind in this general expedition, that 

 do not depart till eight or ten days after the rest. These are 

 chiefly the latter weakly broods, which are not yet in a condition 

 to set out. They are sometimes even too feeble to venture till 

 the setting in of winter ; while their parents vainly exhort them 

 to efforts which instinct assures them they are incapable of per- 

 forming. Thus it often happens that the wretched little fami- 

 lies, being compelled to stay, perish the first cold weather that 

 comes ; while the tender parents share the fate of their offspring, 

 and die with the new-fledged brood. 



Those that migrate are first observed to arrive in Africa, as 

 Adanson assures us, about the beginning of October. They are 

 thought to have performed their fatiguing journey in the space 

 of seven days. They are sometiuies seen, when interrupted by 

 contrary winds, wavering in their course far off at sea, and light- 

 ing upon whatever ship they find in their passage. They then 

 seem spent with famine and fatigue ; yet still they boldly ven- 

 ture, when refreshed by a few hours rest, to renew their flight, 

 and continue the course which they had been steering before. 



These are facts proved by incontestable authority ; yet it is a 

 doubt whether all swallows migrate in this manner, or whether 

 there may not be some species of this animal that, though exter- 

 nally alike, are so internally different as to be very differently 

 affected by the approach of winter. We are assured from many, 

 and these not contemptible witnesses, that swallows hide them- 

 selves in holes under ground, joined close together, bill against 

 bill, and feet against feet. Some inform us, that they have seen 

 them taken out of the water, and even from under the ice, in 

 bunches, where they are asserted to pass the winter, without 

 motion. Reaumur, who particularly interested himself in this 

 inquiry, received several accounts of bundles of swallows being 

 thus found in quarries, and under the water. These men, there- 

 fore, have a right to some degree of assent, and are not to lose 

 all credit from our ignorance of what they aver. 



All, however, that we have hitherto dissected, are formed 

 within like other birds ; and seem to offer no observable variety. 

 Indeed, that they do not hide themselves under water, has been 

 pretty well proved by the noted experiment of Friscii, who tied 



