432 CLASS AVES. 



to carry. There is, however, within this protuberance, and 

 on the upper mandible, the rudiment of a bone, but extremely 

 porous and light ; and this rudiment becomes graduated in 

 proportion to the size of the protuberance in the different 

 species, and in the same species at dijBPerent periods of its age. 



The cutting edge of these large bills is naturally indented ; 

 but in consequence of their brittleness, and thinness, they 

 become much more and irregularly jagged by use; the 

 homy case of the bill, however, like the nails and hoofs of 

 quadrupeds, is constantly growing, and thus the accidental 

 injuries done to the edges are as constantly repaired. 



M. Levaillant found the dissected head of a large rhinoceros 

 hornbill to weigh four o\mces, and that of a raven, more than 

 one ounce, although the size of the former was twenty times 

 that of the latter, and hence he satisfactorily inferred that the 

 bony substance of the hornbill must be much less compact 

 than that of the raven, and in all probability of all other 

 birds whose bill is of moderate dimensions. 



The Rhinoceros Hornbill is the largest, and attains four 

 feet in length, with an expanse of wings of about three feet. 

 The bill is nearly a foot in length ; and, stuck on it, as it were, 

 at the base of the upper mandible, is a second bill, or pro- 

 minence, which is turned upwards and backwards, like the 

 horn of the rhinoceros. 



Notwithstanding the formidable appearance given to this 

 bird by its monstrous bill, it is utterly useless to it as a 

 weapon ; and the bird itself is of too cowardly a disposition 

 to make use of it oiFensively, even if it were more effective. 

 It advances by leaps, and displays in general every appear- 

 ance of cowardice and stupidity, except indeed when ft)od 

 is offered, which causes it to assume a momentary air of con- 

 fidence and vivacity by spreading the wings, opening the 

 monstrous bill, and uttering a cry of satisfaction, feeble 

 indeed for a bird of its dimensions. Levaillant had an oppor- 

 tunity of seeing one at the Cape in a vessel which touched 



