Ornithology, is that science which treats of birds ; describing their form, animal economy, and various uses.

Having already specified the natural habits, as well as the useful purposes, together with the opposite qualities, of the feathered tribe, under many individual names of birds, and especially those which are natives of Britain, in the preceding alphabet of this work, we shall, at present, only subjoin a few general observations, and conclude with an enumeration of the most remarkable objects of this class; the characters of which have been stated in vol. i. p. 58.

Although birds are, by their peculiar form, distinguished from all other creatures, yet their internal structure, in many respects coincides with that of mammillary animals. Thus, both have a heart with two ventricles and two auricles ; red, warm blood ; and solid bones; bones; but which, in the former, are almost uniformly hollow, and contain no marrow. Through these concave bones, the air communicates with the lungs, that are grown together with the back and the ribs; being connected with different cellular webs, which serve as reservoirs of air. - The flesh of birds also resembles that of the mammillary tribe; but the urine of the former, though secreted in the kidnies, is evacuated by the same canal through which their excrements are discharged : nor is their bile collected in a peculiar gall-bladder; for it is, in most instances, conveyed from the liver directly to the intestines.

The stomach of birds is either furnished with a hard membrane for grinding their food ; which is the case with all such as subsist on grain; or, it has the power of dissolving their aliment, by the gas-tric liquor secreted in all carnivorous birds, being similar to that found in the digestive organs of men and quadrupeds ; but the former possess the advantage of spontaneously vomiting hair, feathers, and other indigestible matters.

The instinct displayed by every species of birds, in constructing permanent and artificial nests, in the most appropriate spots, deserves the admiration of contemplative minds ; though such proofs of providential care, and wisdom, are often regarded with indifference : this extraordinary effort to propagate their species, in the most convenient manner, is the more remarkable, as almost every genus of these creatures build habitations of a peculiar form, and with the most proper materials. Another diversity prevails in the shape, colour, and number of their eggs ; the deficiency of which the female supplies, in case one or more have been robbed from her nest. Nor is the migratory instinct of many birds, in autumn, less surprizing ; for, at the approach of winter, they often retire to more genial climes, in order to avoid the hardships arising from cold weather and want of food ; both being removed on their return in the spring. This wonderful propensity is evident, even in those creatures which are confined in cages ; and which, at that season evince an unusual degree of anxiety and turbulence, in their captive state.

Lastly, it deserves to be noticed, that all birds are once, and many kinds of them twice, annually, subject to a change of their feathers, which is commonly termed the moulting season : this distemper arises from an obstruction in the alimentary ducts of the quills, beneath which nutritive matter accumulates, and thus forcibly propels the feathers. At this period, birds appear diseased, or in a state similar to that proceeding from the obstructed oleaginous gland, which is situated above their fundament; and which secretes an oily fluid designed to lubricate their downy-coat ; thus enabling them to resist moisture.

Without these charming warblers, the most beautiful and fertile regions of the earth would exhibit a silent, and often dismal, scenery. How much, therefore, are mankind indebted to these airy companions of their journey through life ! - Male birds greatly surpass the females in beauty, song, and size; excepting in those of prey; where, in general, the contrary prevails. Many species of the winged tribe are so remarkably docile, as to imi tate human speech, and to learn melodious tunes. But, independently of the pleasure thence derived, they are farther of material service to the inhabitants of a country, more especially in hot climates, by destroying myriads of insects, and devouring carcasses ; which would otherwise prove an intolerable nuisance. The occasional mischief and damage committed by some kinds of birds, on the fruits of fields and gardens, is amply counterbalanced by their extensive services in general. Hence, numerous species which furnish us, either with their palatable flesh and eggs, or with their useful feathers, have been gradually domesticated, so as to become the inmates of our habitations ; and particularly those which recommend themselves, either by their beautiful plumage, or by the sweetness of their harmonious strains.

In order to afford a view of the principal kinds belonging to this interesting class of animals, we have been induced to present the reader with the following arrangement :

I. Domestic and Tame Birds: - Cock and Hen ; Turkey ; Goose; Duck; Swan ; Pigeon ; Peacock ; Pheasant ; Guinea-hen, etc.

II. Wild, useful Birds: - Bustard ; "Woodcock ; Grouse; Heath-cock ; Partridge ; Quail ; Lark ; Throstle ; Ortolan ; Stirling, etc.

III. Singing Birds : - Nightingale; Hedge-sparrow; Red-breast; White and Yellow Wagtail; Wren; Gold-crested Wren; Canary-bird; Greater Red-pole ; Chaffinch and Brambling; Goldfinch, Siskin; Fly-catcher; Bullfinch; Greenfinch ; Titmouse; Swallow, etc.

IV. Marshy and Aquatic Birds: - Crane.; Stork ; Grey Heron ; Bittern; Gull; King-fisher; Snipe; Lapwing ; Water hen, etc.

V. Birds of prey : - Eagle ; Falcon ; Owl; Butcher-bird ; Raven; Crow ; Jack-daw; Magpie ; Nutcracker ; Garrulous Roller; Woodpecker ; Bee-eater; Haw-finch ; Oriole or Cherry-bird; Sparrow, etc.