262 NATURAL HISTORY 



When brown owls hoot, their throats 

 swell as big as an hen's egg. I have known 

 an owl of this species live a full year with- 

 out any water. Perhaps the case may be 

 the same with all birds of prey. When 

 owls fly they stretch out their 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 pre- 

 sume 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, 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 re-publication 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. 



