8 
ADVERTISEMENT. 
our three hundred and twenty species described in one 
volume of the size prescribed for the present series of 
use. I have, therefore, devoted a volume to the Terres- I 
trial and another to the Aquatic species, prefixing to the | 
first a short Introduction to the Study of Ornithology, | 
including all the particulars requisite to enable one not ; 
previously acquainted with the subject to compare the ' 
objects with their descriptive characters. Although, in 
a strictly scientific point of view, the division of birds into 
those of the land and water is not commendable, it is con- 
venient, and in some degree natural and familiar. I 
The Classification of Birds is a subject of much dis- 
pute. In fact, no two authors follow precisely the same ! 
plan, or use the same nomenclature. In this state of un- | 
certainty, I have had recourse to nature, and endeavoured j 
to elicit a method which may be at least intelligible. In | 
some instances I have altered the names, conceiving them | 
to be erroneous, or inconsistent ; but in every case, the 
popular, and some of the scientific, appellations are given. , 
The generic characters, as well as those of the orders, j 
include some particulars, especially with reference to the 
digestive organs, not given in other works, but easily in- 
telligible, and of great importance as indicative of the 
mode of life of the species. Those who are desirous of 
obtaining more extended information on this subject, I 
refer to the only^ork known to me in which they will 
find it, my History of British Birds, of which three vo- 
lumes, incltiding all the species referred to in this Manual, 
have recently been published. 
Manuals, the characters would be too brief to be of much 
Edinburgh, 2bth October 1840 . 
