16 FALCONID^l. 



light, the relative proportions of the lens are as six and 

 seven- tenths to seven and eight-tenths ; and in the Swan, 

 which has to select its food under water, the proportions 

 of the lens are as three to three and eight-tenths. Birds 

 have also the power of altering the degree of the con- 

 vexity of the cornea. With numerous modifications of 

 form, aided by delicate muscular arrangement, birds 

 appear to have the power of obtaining such variable 

 degrees of extent or intensity of vision as are most in 

 accordance with their peculiar habits and necessities. 



The Golden Eagle makes a flattened platform nest, 

 or rather a collection of strong sticks, on the high and 

 most inaccessible part of rocks, and requiring a space of 

 several square feet of surface. The female bird, which 

 is considerably larger than the male, lays two, and 

 sometimes three eggs, towards the end of the month of 

 March or the beginning of April. If the eggs are 

 removed, it is said that the bird does not lay any more 

 that season. The egg is about three inches long by two 

 inches and five lines broad, of a dirty white colour, 

 slightly mottled nearly all over with pale reddish brown. 

 An egg of this bird in the collection at the British 

 Museum is so marked ; and a representation of the egg, 

 in the excellent work of my friend Mr. W. C. Hewitson 

 oil the Eggs of British Birds, is very correctly drawn 

 and coloured. Incubation with the Golden Eagle, ac- 

 cording to Mr. Mudie, lasts thirty days, and the young 

 Eaglets are at first covered with greyish white down. 

 They are watched, defended, and plentifully supplied 

 with food by the parent birds. Smith, in his History 

 of Kerry, relates that a poor man in that county got a 

 comfortable subsistence for his family during a summer 

 of famine out of an Eagle's nest, by robbing the Eaglets 

 of part of the food the old ones brought, whose at- 



