1 6 FALCONIDjE. 



the lens are as six and five-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 convexity of the cornea. With 

 numerous modifications of form, aided by delicate muscu- 

 lar arrangement, birds appear to have the power of ob- 

 taining 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 consi- 

 derably 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 on the Eggs of British Birds, 

 is very correctly drawn and coloured. Incubation with 

 the Golden Eagle, according 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 the food the old ones brought, whose at- 



