92 CLASS AVES. 



» 

 flying continually to and from near the surface of the water, 



without departing any distance from their nests in the neigh- 

 bouring banks. They seem, like their congeners, to have 

 or three broods in a season. 



Spallanzani tried a similar experiment on this species as he 

 had previously done on the swallow and marten. Having drawn 

 a male and female from the nest at the extremity of the hole, 

 by means of a hooked wire, he carried them from Pavia to 

 Milan ; and having arranged with a friend the precise moment 

 when they were to be set at liberty at the latter place, they 

 were seen to enter the hole again exactly thirteen minutes 

 after their departure ; and, by means of silken threads, the 

 same pair were observed to return the following season to the 

 same hole. 



It has been thought that this species is more hardy than 

 the rest, and hibernates in the hole in which it breeds ; but many 

 of these holes have been inspected in the winter, and no birds 

 have been found : nor does there seem any good reason to con- 

 clude that they differ from the swallow and marten in anything 

 more essential, than those two species differ from each other ; 

 the sand-bank distinguishes these from them, as the window 

 and the chimney distinguish them from one another. It will 

 be observed, however, by his language in the text, that the 

 Baron is inclined to a contrary opinion. 



The Purple Swallow {Hirunda purpurea. Lath.) is a 

 beautiful species. At first sight it appears altogether black, 

 but its plumage, far from being uniform, varies according to 

 the position of the eye which observes it, and the movements 

 of the bird, and casts the most brilliant reflections of blue, 

 violet, and purple. 



This swallow is protected by the Americans with great 

 justice. It not only diminishes the number of winged insects 

 which cause so much inconvenience, but it warns the poultry 

 of the approach of birds of prey. The instant one of the 

 latter makes his appearance, these swallows all assemble, g,nd 



