120 THE ADVENTURES OF 



" What frightful creatures !" cried Lucien. " I can't 

 think why the nasty smell does not drive them away." 



" It is just the reverse ; it is the smell which attracts 

 them," I replied. "Even when they are soaring high up 

 in the sky, and scan the horizon with their yellow eyes, 

 their subtle sense of smell enables them to catch the effluvia 

 of the putrefied matter on which they feed." 



In some of the towns of Mexico the black vultures are so 

 numerous living there, as they do, almost tame in the 

 streets that our young companion was well acquainted 

 with these birds ; but he had never been present at one of 

 their joint meals. The sight of one of their bare, black, 

 and wrinkled necks, plunged into the body of the animal, 

 made him almost ill. 



" Poh ! what disgusting birds !" he cried. 



" You are wrong," I said ; " the birds are only obeying 

 the instinct implanted in them. Henceforward you will 

 understand better the name of the ' rapacious order ' or 

 4 birds of prey,' which is given by naturalists to vultures, 

 eagles, falcons, and owls. You are aware that the science 

 which describes the habits of birds is called ornithology. 

 Cuvier, the great classifier, divides the feathered tribe into 

 six orders birds of prey, passerines, climbers, gallinaceans, 

 wading, and web-footed birds. In order to prevent confu- 

 sion, the orders have been subdivided into families, the fami- 

 .lies into groups, the groups into genera, and the genera into 

 species. 



" How are they all to be recognized ?" 



" By the study of certain special characteristics, which 

 serve as distinguishing marks. Birds of prey, for instance, 

 have curved beaks and claws, legs feathered either to the 

 knee or down to the foot, three toes in front, and one be- 

 hind ; also, the back and inside toe are stronger than the 

 others. The vultures which you are looking at, the only 



