OF SELBORNE. 247 



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. 



I am, &c. 



It will be proper to premise here that the sixteenth, eighteenth, twen- 

 tieth, and twenty-first letters have been published already in the Philo- 

 sophical 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 imperfect 

 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 Guayaquil 2 , 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. Whoever contemplates the 

 myriads of insects that sport in the sunbeams of a 

 summer evening in this country, will soon be convinced 

 to what a degree our atmosphere would be choked 

 with them was it not for the friendly interposition of 

 the swallow tribe. 



Many species of birds have their peculiar lice; but 

 the Hirundines alone seem to be annoyed with Dipte- 

 rous insects, which infest every species, and are so 

 large, in proportion to themselves, that they must be 



2 See Ulloa's Travels. 



