Darwin further tells us that “in diving, its little wings are used as fins; but on the land as front legs. When crawling, it may be said, on four legs through the tussocks, or on the side of a grassy cliff, it moves so very quickly that it might easily be mistaken for a quadruped. When at sea, and fishing, it comes to the surface for the purpose of breathing with such a spring, and dives again so instantaneously, that I defy anyone, at first sight, to be sure that it was not a fish leaping for sport.” These observations were made by Darwin during his famous voyage round the world in the _Beagle_, which lasted five years, and of which he has given us the delightful account, from which this passage is taken. The commander of the _Beagle_ was Captain FitzRoy, who has also told us something about the penguins. He says that, when feeding its young, “the old bird gets on an eminence, and makes a great noise between quacking and braying, holding its head up in the air, as if it were haranguing the penguinnery” (a much better word, I think, than the “penguin-rookery”), “while the young one stands close to it, but a little lower. The old bird, having continued its chatter for about a minute, puts its head down and opens its mouth widely, into which the young one thrusts its head, and then appears to suck from the throat of its mother for a minute or two, after which the chatter is again repeated, and the young one is again fed.” CHAPTER IV WONDERFUL BIRDS’-NESTS—A CITY OF GRASS—BIRD WEAVERS AND TAILORS—BIRDS THAT MAKE POTTERY—EVOLUTION IN BIRD-ARCHITECTURE.