AMERICAN KDITOB. 307 



fields, more especially if he lie motionless on his back in 

 the position of a lifeless body, a raven will be found to 

 draw near, and reconnoitre, though unseen a moment 

 before. This fact would seem to confirm the opinions 

 doubted by Mr. Knapp that sight, and not smell, is the 

 sense by which these birds are guided in descending on 

 their prey, since the mere motionless feigning of death 

 is sufficient to attract their attention. It is well known 

 that Mr. Audubon held this opinion, confirming it by 

 experiments with the American turkey-buzzards, which 

 proved quite inattentive to carrion of the most offensive 

 kind when placed immediately before them, so long as it 

 was concealed from their sight by a cloth. Dr. James 

 Johnson and other writers on the subject also doubt the 

 sense of smell in birds of this habit, and other experiments 

 like that of Mr. Audubon have had the same result. 



Owing to the greater care bestowed on the health of 

 cattle at the present day, and their less frequent deaths 

 in the field under the modern system, ravens are said to 

 be sensibly diminishing in England. 



NOTE V. 



THE HOUSE FLY, (musca carnaria,) p. 151. 



The speed of these familiar insects when on the wing, 

 is very remarkable, being computed at a third of a mile 

 in a minute. The peculiarity of their walking, apparently 

 against the laws of gravitation, with such perfect ease, 

 has been the subject of much investigation and contro- 

 versy. Formerly it was believed that the fly walked by 

 means of organs called suckers, which produced a vacuum 

 at the extremity of each foot, by exhausting the air 

 Some lizards are known to climb walls in this way. Bu6 

 it is now more generally believed that the firm hold of 



