180 SWALLOWS. 



legs behind them as a balance to their large 

 heavy heads ; for as most nocturnal birds have 

 large eyes and ears, they must have large heads 

 to contain them. Large eyes, I presume, are 

 necessary to collect every ray of light, and large 

 concave ears to command the smallest degree of 

 sound or noise. 



in a state of nature, and during summer washing almost 

 daily. W. J. 



It will be proper to premise here, that the sixteenth, 

 eighteenth, twentieth, and twenty-first letters have been 

 published already in the Philosophical Transactions ; but 

 as nicer observation has furnished several corrections and 

 additions, it is hoped that the republication of them will not 

 give offence ; especially as these sheets would be very imper- 

 fect without them, and as they will be new to many readers 

 who had no opportunity of seeing them when they made 

 their first appearance. 



The hirundines are a most inoffensive, harmless, 

 entertaining, social, and useful tribe of birds ; 

 they touch no fruit in our gardens ; delight, all 

 except one species, in attaching themselves to 

 our houses ; amuse us with their migrations, songs, 

 and marvellous agility ; and clear our outlets from 

 the annoyances of gnats and other troublesome 

 insects. Some districts in the South Seas, near 

 Guiaquil *, are desolated, it seems, by the infinite 

 swarms of venomous mosquitoes, which fill the 

 air, and render those coasts insupportable. It 

 would be worth inquiring, whether any species 

 of hirundines is found in those regions. Who 



1 See Ulloa's Travels. 



