LONGEVITY. 219 



it betakes itself to a rock or rough stone, and rubs 

 its beak till the overgrown part is ground down into 

 proper proportion. 



Albertus Magnus gives a still more ingenious pro- 

 cess of renewal, not, however, of his own inven- 

 tion, but quoted from Jorachus and Andelinus, whose 

 works, we presume, are now lost. "They say," 

 reports Albertus, " that an old eagle at the period 

 the young ones are fledged, as soon as she has dis- 

 covered a clear and copious spring, flies directly 

 upward, even to the third region of the air, which 

 we term the region of meteors, and when she feels 

 warm, so as to be almost burning, suddenly dash- 

 ing down and keeping her wings drawn back, she 

 plunges into the cold water, which, by the astringing 

 of the external cold, increases the internal heat. 

 She then rises from the water, flies to her nest, and 

 nestling under the wings of her warm young ones, 

 melts into perspiration, and thence with her old 

 feathers she puts off her old age, and is clothed 

 afresh; but while she undergoes this renovation, 

 she makes prey of her young for food. But I can 

 only," he adds, " consider this as a miraculous oc- 

 currence, since in two eagles which I kept I ob- 

 served no changes of this sort ; for they were tame 

 and docile, and moulted in the same manner as 

 other birds of prey." 



It is very obvious that all these are mere fancies, 

 and farther, that there are few or no data by which 

 to determine the age of wild birds. We have, in- 

 deed, observed among house-sparrows individual 

 cockbirds, in which the black markings were inter- 

 mixed with white feathers: but whether this was 

 the hoariness of age, or merely an accidental va- 

 riety of colour, we had no means of ascertaining. 

 It has been long decided that the grayheaded crow 

 is not an old carrion crow grown hoary with age as 

 is popularly believed ; but a different species (Cor- 

 vus comix). 



