248 FACULTIES OF BIRDS. 



soaring to an altitude. In this situation, their prey 

 on the ground is seen by them, however minute it 

 may be, and their appearance is merely their de- 

 scent from high regions of the atmosphere to within 

 the scope of our optics." 



With respect to the smell of vultures, Willoughby 

 says, " they have an excellent sagacity of smelling 

 above all other birds, so that they can perceive the 

 savour of dead carcasses from far," to which Ray 

 adds, " many miles off they say."* Some of the old 

 authors, indeed, such as Thomas Aquinas, specify 

 the distance at which a vulture can scent out a 

 dead body to be five hundred miles, and Isidore al- 

 leges it is no matter even if the sea itself intervene. 



It may well be disputed, however, that the smell 

 of the vulture or any other bird extends to the dis- 

 tances alleged by these writers, for, as was long 

 ago remarked by Caelius Rhodiginus, odorous efflu- 

 via cannot be distinguished at any considerable dis- 

 tance, as they are not only diluted by being diffused 

 in the air, but may even be thereby wholly changed 

 in their qualities. The observations of Avicenna 

 are still more to the point. "I have," he says, 

 " observed vultures wheeling about in the air, and, 

 of course, their vision must be extensive, to enable 

 them to see from a higher elevation than the highest 

 mountains, since they can in such circumstances 

 discern a piece of carrion in the plains below them. 

 But if it is denied that colours can be perceived at 

 such distances, much more ought the same to be 

 affirmed of odours, whose power is weaker than 

 that of colours." 



From all these various facts, we think Dr. John- 

 son's remarks are decidedly the most plausible; 

 and even those authors who speak in the most un- 

 hesitating manner of the powers of smell, furnish 

 from their own accounts circumstances to prove 



* Ornith., by Ray, p. 66. 



