PREFACE 



TO THE SIXTH EDITION. 



I HAVE endeavoured, in this edition, to give the 

 natural history of the Swallow in general, in addi- 

 tion to the observations in the foregoing editions, 

 on its brumal retreat. I have also added what is 

 known of the remaining species of the genus, both 

 with the view to make this monograph as perfect 

 as possible, and to render the distinctive characters 

 of the different species more familiar to those who 

 may observe, or may be of assistance in determining, 

 the brumal place of the Swallow, by noticing it on its 

 passage, or by discovering it in its torpidity : since, 

 from the indefinite descriptions of many of the 

 ancient naturalists, it is often very difficult to ascer- 

 tain the particular species of which they treated. 

 And I have interspersed the whole tract with numer- 

 ous new observations. 



