274 THE UNIVERSE. 



" These nests," says Pliny, " are worthy of admiration ; 

 they have the shape of a ball and resemble a large sponge. 

 They cannot be cut with iron, but a violent shock shivers 

 them." Plutarch believed that they were composed only 

 of fish-bones interlaced ; but it appears that the philosopher 

 mistook the carapaces of the sea-urchin, which are often 

 brought ashore by the waves, for the nests of the Halcyon. 



Though it is now well known that the Halcyon of an- 

 tiquity, which is nothing more than our kingfisher, does 

 not commit a floating nest to the sea, the ardent ornithol- 

 ogists who study the habits of the dwellers in our fens 

 have discovered some species, the marvellous nidification 

 of which outstrips even that fabled to be practised by the 

 Halcyon. 



This is the case with the nest of the little grebe. This 

 swimming bird hatches its young upon a regular raft. It 

 is a mass of strong stems of aquatic plants closely united to- 

 gether, and as these contain a considerable amount of air 

 in their ample and numerous cells, and as, in addition, they 

 set free gases during the process of rotting, these aeriform 

 fluids, imprisoned by the plants, make the nest lighter than 

 water. It is found floating in lonely spots where the tall 

 rushes and great reeds grow. There, in her improvised 

 craft, the female, upborne on her watery bed, tranquilly 

 broods on her offspring. But if any intruder happen to dis- 

 cover her, if anything threaten her safety, the wild bird 

 plunges one of her feet into the water, and makes use of it 

 as a paddle, with which she transports her dwelling to a dis- 

 tance. The little sailor guides her frail skiff whither she 

 likes, sometimes dragging along a perfect sheet of water- 



