there was a nest , an incoherent straggling mass of twig and straw on the outside , but inside , a hollow of mud as smooth as the feathered breast of the bird that had rounded it out ; and in that hollow , three eggs , pale greenish blue , a blue he 'd never seen in sky or sea , a blue that was somehow sad , and unique to these microcosms glowing against the dirty brown-grey of the nest .