102 
INTRODUCTION. 
thologist that the classification here employed will 
be in conformity with that theory, on the principles 
of the natural system, which we have already given 
to the world in other works*. The species will 
be arranged under their natural families ; and when 
they possess any remarkable relations, not hitherto 
observed, occasional notices on these points will be 
introduced. Commencing with the Raptorial order, 
or the 
BIRDS OF FRET, 
we find several species mentioned by different 
authors as inhabiting Senegal, which we are com- 
pelled to omit ; partly because we cannot vouch for 
their locality, not having seen imported specimens ; 
but more especially because we studiously avoid, on 
nearly all occasions, copying from others the de- 
scriptions of animals we have never seen, a custom 
which has led, in a great number of instances, to 
erroneous accounts, drawn up at a time when the 
science was emerging from its infancy t. Our work 
may thus be thought to loose something in the 
variety of its materials, but this we trust will be 
compensated by its greater originality and accuracy. 
Besides, we desire to make our volume not only 
* Fauna Boreali Americana, or Northern Zoology ; Clas- 
sification of Animals, &c. 
t Even some of the best ornithologists pay so little atten- 
tion to the variations of structure, and pass over so many 
points necessary to be understood, that their descriptions are 
of little service beyond informing us on the mere colours of 
the plumage. Those for instance, in the Planches Colo, csoi 
MM. Temminck and Langier, are particularly defective in this 
respect 
