OF SELBORNE. 187 
ears to command the smallest degree of sound or 
noise. 
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 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 mar- 
vellous agility ; and clear our outlets from the an- 
noyances of gnats and other troublesome insects. 
Some districts in the South Seas, near Guyaquil,* 
are desolated, it seems, by the infinite swarms of 
venomous moschetoes which fill the air, and render 
those coasts insupportable. It would be worth in- 
quiring whether any species of hirundines is found 
in those regions. Whoever contemplates the myr- 
iads of insects that sport in the sunbeams of a 
summer evening in this country, will soon be con. 
vinced to what degree our atmosphere would be 
choked with them was it not for the friendly inter- 
position of the swallow tribe. 
Many species of birds have their peculiar lice ; 
but the hirundines alone seem to be annoyed with 
dipterous insects, which infest every species, and 
are so large, in proportion to themselves, that they 
* See Ulloa’s Travels. 
