16 FALCONID A. 
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 mtensity 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; anda 
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 Hagle, according to Mr. Mudie, lasts thirty 
days, and the young Haglets 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- 
