2 ON THE CLASSIFICATION OF BIRDS. 
place of temporary rest, in their voyage through the 
regions of space, than as their permanent abode. They 
remind us of those invisible spirits of the unseen world, 
which, we are taught to believe, traverse the air on the 
wings of the wind; who alight, but for a moment, 
among the sons of men, and then depart to breath a 
purer atmosphere. Of all unintelligent beings, they 
alone are gifted with a musical voice, possessing both 
sweetness and varied expression. Their language, in 
some measure, is thus intelligible even to man, in- 
spiring him with cheerfulness or melancholy. Plence 
it is, that from among birds the poets have selected 
their sweetest themes. They are, both poetically and 
literally, the butterflies of vcrtebrated animals* ; flitting 
from one plant to another, living less on earth than in 
the air, and having their wings ornamented with fea- 
thers of bright or varied colours. In both we dimly 
see an indication of that existence which will separate 
the spirit of man from those cares, anxieties, and al- 
lurements which chain him down to earth, as if it was 
his final and only stage of action. It is highly pro- 
bable that the “ Sweet Psalmist of Israel -j- ” hatl some 
such thought, when he longed for the wings of the 
dove, that he might flee from earth and be at rest.;j; 
(2.) It is to this interesting and varied class of 
animals that our present volume will be exclusively 
dedicated. Our chief object will be to explain those 
relations which they bear to other animals, and those 
which they possess among themselves. We shall en- 
deavour to exhibit Ornithology, not as an isolated 
science, disconnected in its relations from other classes of 
the animal kingdom, and whose parts are to be classed 
without any reference to general laws ; but we shall 
view it as a part only of one “ stupendous whole,” — 
as forming an integral portion of that mighty circle 
over which the same laws of physical science equally 
* The feathers of birds, soft and imbricate, are perfectly analogous to 
the down upon the wings of butterflies, and both are disposed in the same 
manner. 
t Bishop Horne. t Psalm xi. L and Iv. 6. 
