PREFACE. 
The system of classification followed in this little book is 
that of Mr. G. R. Gray^ in his great and invaluable work, 
^The Genera of Birds/ To have given, even in the brief- 
est manner, the distinguishing characters of the numerous 
families and sub-families into which the extensive class of 
Birds is divided, would have taken up nearly all the space 
of the Work. Accordingly, this part of the subject, as in 
the previous volume on Mammalia, is treated very suc- 
cinctly, while the space is occupied with interesting details 
on the habits of the various groups, compiled chiefly from 
the works of recent observers. In Ray^s ^ Wisdom of God 
manifested in the Works of the Creation,^ pubhshed about 
a century and a half ago, the author estimated the number 
