156 NATURAL HISTORY. 



wheeling with wonderful velocity, occasionally soaring 

 very high, and uttering its shrill screams. It captures 

 great quantities of insects to give to its young, retaining 

 them in a kind of pouch under the tongue. Our Chim- 

 ney Swallow is one of the Swifts. It is a social bird, ap- 

 pearing in flocks, and making its nest in tall hollow 

 trees or in unused chimneys. It is amusing to see them 

 go into a chimney. The flock wheels round and round, 

 and as they come down near the chimney those that are 

 lowest drop in at each turn till the whole have descend- 

 ed. The Bank Swallow, or Sand Martin, which we see 

 so often making holes in sand-banks with its awl-shaped 

 bill, has its counterpart in Europe. The Martins, which 

 so familiarly inhabit the boxes set up for them by man, 

 are Swallows. Appearing in the extreme south of the 

 United States the first part of February, they arrive in 

 New England the latter part of April, and in May they 

 are seen as far north as Hudson's Bay. They begin to 

 emigrate from thence southward in August.* 



257. The Todies are birds of gaudy plumage and rapid 

 flight, restricted almost entirely to tropical regions. 



* There is one species of Swallow which furnishes a singular arti- 

 cle of diet, highly prized by the Chinese. This article is the nest of 

 the bird. The chief material of which the nest is composed has been 

 a subject of much dispute, some supposing it to be a kind of sea- weed, 

 and others a substance derived from the spawn of fishes. " It is now 

 ascertained," says Carpenter, "that this substance is secreted by enor- 

 mously developed salivary glands ; a few fragments of grass, hair, and 

 other substances are generally mixed with it. The purest nests con- 

 sist almost entirely of gelatinous matter, which, dissolving readily in 

 water, is employed in making rich soups and gravies. The collecting 

 of these nests is a proceeding of great danger; but a large number of 

 persons are employed in it, as may be judged from the quantity sent 

 to China. About 27,000 Ibs. are annually transmitted from Java, 

 and these are of the best quality. A still greater quantity is obtained 

 from the Suluk Archipelago, and much, also, from Ceylon and New 

 Guinea. It is calculated that about 30,000 tons of Chinese shipping 

 are engaged in the traffic, and that the value of their freights is above 

 280,000." 



