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first killed they do not sink to the bottom like quadrupeds, 

 hut Hoat on the surface until the carcase either rots away or 

 U devoured by prcdaceous unitiiaU.' 



We will begin with an instance affording pood evidence 

 of the existence of a bird which. notwithstanding the con- 

 current testimony of authors, catalogues, and even speci- 

 mens, the latter indeed now reduced to fragments has 

 been considered by some the, mere creature of imagination. 

 M. Desjardms found, under a bed of lava in the Isle of 

 France, the head, breast-bone, ami huraerus of a bird, \\ Inch 

 C'uucr pronounced to be part of the remains of the dodo. 

 These bones were in the midst of others belonging to the 

 large existing species of land-tortoiso named Tettudo In- 

 dica. [See DODO.] 



The hawks at the northern extremity of the rock of Gib- 

 raltar, among other rejectamenta of their food, drop into the 

 fissures the bones of small birds, which gradually become 

 incorporated into an osseous breccia. 



Our attention is next drawn to the ossiferous caverns. In 

 that of Kirkdale, for instance. Professor Buckland found, in 

 company with the bones of carnivorous, pachydermatous, 

 ruminant, and rodent quadrupeds, the remains of the raven, 

 pigeon, lark, a small species of duck, and a bird of about 

 the size of a thrush. 



We next come to the marine supracretaceous rocks of 

 the South of France, in the sands or upper strata of which 

 M. Marcel de Serres found the remains of birds, accom- 

 panied by abundant relics of terrestrial and marine mammi- 

 fers. reptiles, fish, some wood, and oysters and Balani. 



The remains of birds also occur in the gypseous beds, and 

 fresh-water marls of the supracretaceous group. 



But perhaps the most interesting discovery relative to 

 these remains was made by MM. Croizet and Jobert, who 

 found in the fresh-water sands, clays, and limestone in the 

 neighbourhood of the town of Issoire (Puy de D6me), in 

 company with the hones of quadrupeds, &c., the remains of 

 three or four birds, and also their eggs, in a perfect state of 

 preservation : M. Bertrand Roux, now M. Bertrand de 

 Doue, had previously observed their hones in the fresh- 

 water rocks at Volvic. 



Upon the whole we may reckon nine or ten extinct 

 species of birds in the Eocene period of Lyell. These belong 

 to the birds of prey properly so called, the gallinaceous 

 birds, the waders, and the swimmers. Eggs of aquatic 

 birds occur in the Eocene lacustrine formation in Auvergne. 



We arc not aware that any hones of birds have been re- 

 corded in strata of greater antiquity than the tertiary, with 

 the exception of the fragments found by Mr. Mantell in the 

 weald of Sussex. The so-called birds' bones of Stonesfield 

 are the bones of Pterodactyles. [See PTERODACTYLS.] 



BIRD'S-EYE VIEW, a mode of perspective represen- 

 tation, which may be divided into two kinds, proper and 

 improper. The latter of these, the one most generally 

 employed, differs from ordinary perspective delineation, in 

 nothing else than in the horizon being taken much higher 

 than usual ; the horizontal line, and of course the point of 

 sight, is either placed above the picture, or the level of the 

 ground is supposed to be considerably below the base of 

 the picture. The objects thus shown, whether buildings or 

 landscape, or both combined, appear as they would do if 

 viewed from some lofty station, from the summit of a build- 

 ing, from a terrace, tower, or any other eminence ; but still 

 the spectator is supposed to be looking in a straightforward 

 direction, and the plane of the picture to be perpendicular 

 to the natural horizon. Consequently, only distant objects 

 can thus be shown, because, when looking in that direction, 

 a person cannot possibly see objects immediately beneath 

 him. He can do that only by looking down upon them : 

 but in a picture there can be but one instant of view, nor 

 can the point of sight be shifted at pleasure, by the eye 

 being directed upwards or downwards, so as to alter the field 

 of vision, and take different objects in succession. What- 

 ever is shown in a picture must be supposed capable of 

 being embraced by the eye at once; although in practice 

 some little degree of license in this respect is occasionally 

 allowable. 



If it be desired (o show the objects immediately below 

 the spectator, so as to give a distant view of the tops of 

 buildings so situated, and of parts that would otherwise be 

 concealed from sight, recourse must l>e had to the first- 

 mentioned mode, namely proper bird's-eye perspective. 

 This is the reverse of that employed for ceiling-pieces, 

 termed di totlo in tu ; for as there objects are fore-short- 



ened as seen from below, so in the bird's-eye they are fore- 

 shortened, as if viewed from above. This species of ' birdt- 

 i i/i 1 ' might therefore with great propriety be distinguished by 

 the name of prone perspective, or looking downwards ; and 

 the di sotto in *, by that of supine perspective, or looking 

 upwards. In like manner as in ceiling perspectives, the 

 plane of the picture becomes parallel to the natural horizon, 

 instead of vertical, so does it in a proper birft-eye view ; 

 with this difference, that in the former c;i- is be- 



neath the picture and looking up to it; in the latter, over it, 

 and looking down upon it ; at least, if not exactly lu>ri- 

 zontal, the plane of the picture must be more or less in- 

 clined, accordingly as the eye is supposed to look down 

 more directly or obliquely ; because the jitane of projection 

 or picture must be assumed as perpendicular to the central 

 ray from the eye. The relative position of objects to each 

 other and to the picture, and of the picture to the eye, are 

 the same in this as in ordinary perspective, the sole differ- 

 ence being that of the spectator's own situation. This \\ ill 

 be apparent if we look into a hollow cube, or box, open cm 

 one side : it matters not whether it be open on one of the 

 upright sides, or on the top. In either case the planes or 

 sides perpendicular to the open side, and the one parallel to, 

 or facing it, will have the same perspective appearance ; only 

 in the one case the plane facing the spectator will be ver- 

 tical, in the other horizontal. In a picture or drawing this 

 will depend entirely upon the artist whether he chooses to 

 represent the plane parallel to the picture as horizontal, 

 that is the ground or floor, and the other planes perpendicu- 

 lar to the ground; or that parallel plane and two of the 

 adjoining planes upright, and the other two horizontal. 

 Again, were a hole bored through the ceiling of a lofty 

 room, a person looking down through it would have a per- 

 fect or proper bird's-eye view both of the apartment and its 

 furniture. Hence, it is obvious that in such representation 

 the floor would answer to what in the common mode of per- 

 spective would be the side or end of the room lacing the 

 spectator; also that the vertical lines of the sides of the 

 room, of doors, windows, legs of chairs, &c., would vanish 

 to some point in the line or plane passing through the eye, 

 exactly as the horizontal lines would do if they were seen 

 according to the usual position. For \inlcss the lines, in 

 this case intended to represent upright ones, were made to 

 vanish, those planes or walls would not be fore-shortened ; 

 and unless that were done they could not be viewed, but 

 the whole would be reduced to a mere plan of the room : 

 just as a common upright view would he reduced to a section 

 or geometrical elevation, if the planes representing the other 

 two walls with the ceiling and floor were not shown per- 

 spectivcly or fore-shortened. Yet, although such perspective, 

 or bird's-eye view, would be correct in itself, it would seem 

 too fanciful and unnatural, if not positively distorted, because 

 the objects would be shown under such very different cir- 

 cumstances from those according to which they are really 

 seen ; consequently, such kind of views would he quite un- 

 pictorial, and merely matters of curiosity. They might 

 nevertheless occasionally be found useful as explanatory 

 diagrams, or drawings, whenever it should be required to 

 show the effect of an interior, as beheld from a lofty upper 

 gallery, not viewed in a cross or straightforward direction, 

 but by looking down into the lower area of the apartment. 

 This prone perspective might also be applied for the purpose 

 of giving a map-like, yet graphic view of a group of buildings 

 and their locality. As a picture, indeed, such view would be 

 extravagant, although as a picture-map it would have some- 

 thing to recommend it. Even the more usual kind of 

 bird's-eye perspective, or view with a very elevated horizon, 

 is by no means the best calculated for picturesque effect, 

 since it brings those parts of an edifice into view which 

 are intended to be concealed, and otherwise greatly takes 

 off from the architectural effect; causing the building so 

 viewed to appear too much like a small model placed upon 

 a table. 



BIRD'S-FOOT TREFOIL. [Sec ORNITHOPUS.] 

 BIRDS-MOUTH. [See MOULDING.] 

 BIRD'S NEST. [Sec LATHR*A and NKOTTIA.] 

 BIREN. [See ANNA IWANOWXA of Russia.] 

 BIRGUS (zoology), a genus of long-tailed crustaceous 

 animals, approaching the hermit crabs (Pagurut) esta- 

 blished by Leach. The following are the leading cha- 

 racters : Middle antcnntr having their second articulation 

 crested or tufted ; feet of the first pair of legs unequal, ter- 

 minated by pincers or knob-claws ; feet of the second and 



