Indeed, it takes a very quick eye, sometimes, to make out the form of the bird as it passes: all that is seen is a sudden trail of sapphire blue, which, meteor-like, vanishes before you have time to say "There it is." And what is its real colour? Sitting opposite you on its perch, the throne from whence this little king surveys its subject fishes, the bird is a beautiful chestnut and white, and its legs and feet are coral red. Then it dives, and as it goes down its plumage flashes a pure, clear blue, and as it comes up, taking the light at another angle, it is a lovely mixture of azure that is half emerald-green and of emerald-green that is half azure. For all these colours go to the painting of a kingfisher; but, as a rule, when it is flying from you it is simply a streak of sapphire. The young birds of the first year have their colours fainter, but even then are sweetly pretty, and there are not many sights in our wild Nature more completely attractive than that of the young brood sitting about close together on the roots among which their nest has been tunnelled out, while the old ones fly backwards and forwards, fishing for them and feeding them. And whatever happens, they all keep on saying "Peep-peep" to one another, in the happiest, contentedest way conceivable. Their nest is a yard back in the bank. It takes the old birds two or three weeks to dig it out (though sometimes they will begin housekeeping in some convenient hole that the water-rat has left or the sand-martin deserted), and at the end of the tunnel, on a flooring of fish-bones, are laid the exquisite white round eggs, with shells so translucent that when they are fresh they look more pink than white. [Illustration: THE CAVE-HAUNTING MARTLET] Yet poets and others who draw so many morals from the pearl being found in what they are pleased to call a "foul" oyster, never allude, strangely enough, to Nature's pretty lesson of the kingfisher, which comes arrayed in all its loveliness of plumage from the very dirtiest of holes. For it is a sad fact that kingfishers have the most magnificent contempt for everything like "sanitary arrangements;" yet once they have left their nests they are the chiefest jewels of the stream, among the prettiest things to be seen in all a summer's day. Where they built was apparently once a mystery, for in the long-ago days of Greece and Rome the "halcyon" was supposed to go off somewhere near Sicily and other isles, and nest upon the open seas; and so fond were both pagan men and pagan gods of the little bird, that--so poets pretended--the seas were never stormy while the halcyons were nesting, and the word has passed into our language as the symbol of calm security and rest and peace. So in Keats: "O magic sleep! O comfortable bird! That broodest over the troubled sea of mind Till it is hushed and smooth." And in Shelley: