484 PLINY'S NATURAL HISTORY. [Book X. 



with its wings, and forces 26 them from time to time to look 

 steadily upon the rays of the sun ; and if it sees either of 

 them wink, or even its eye water, it throws it headlong out 

 of the nest, as being spurious and degenerate, while, on the 

 other hand, it rears the one whose gaze remains fixed and 

 steady. The halisetus 27 is not a species of itself, but is an 

 eagle of mixed breed : hence their produce are of the species 

 known as the ossifrage, from which again is produced the 

 smaller vulture; while this in its turn produces the large 

 vulture, which, however, is quite barren. 



Some writers add to the above a seventh kind, which they 

 call the " bearded" 28 eagle ; the Tuscans, however, call it the 

 ossifrage. 



CHAP. 4. THE NATURAL CHARACTERISTICS OF THE EAGLE. 



The first three and the fifth class of eagles employ in the 

 construction of their aerie the stone aetites, 29 by some known 

 as " gangites ;" which is employed also for many remedial 

 purposes, and is proof against the action of fire. This stone 

 has the quality also, in a manner, of being pregnant, for when 

 shaken, another stone is heard to rattle within, just as though 

 it were enclosed in its womb ; it has no medical properties, 

 however, except immediately after it has been taken from the 

 nest. 



Eagles build among rocks and trees ; they lay three eggs, 

 and generally hatch but two young ones, though occasionally 

 as many as three have been seen. Eeing weary of the trouble 

 of rearing both, they drive one of them from the nest : for 

 just at this time the providential foresight of Nature has denied 

 them a sufficiency of food, thereby using due precaution that 

 the young of all the other animals should not become their 

 prey. During this period, also, their talons become reversed, 

 and their feathers grow white from continued hunger, so that 

 it is not to be wondered at that they take a dislike to their 



26 See Lucan, B. ix. 1. 902. 



27 He contradicts himself, for lie has already stated that it is the sixth 

 species. 



28 " Barbata." Cuvier takes it to be the laemmer-geyer, or Gypaetus, 

 the only hird of prey that has a beard. 



29 Or eagle-stone. See B. xxxvi. c. 39. He does not there mention 

 that it is comhustible. It is not impossible that pieces of aetites, or ferru- 

 ginous geodes, may have been found in an eagle's nest. 



