108 CLASS AVES. 



two minutes, having changed horses one-and-twenty times ; 

 thus the best horses can make no more than four leagues in an 

 hour, nor more than thirty leagues a day. But the swiftness 

 of birds is considerably greater. In less than three minutes 

 we lose sight of a large bird ; of a kite, for example, which pro- 

 ceeds horizontally, or an eagle, vertically, and the diameter of 

 whose extent in flying is more than four feet. From this we 

 may infer, that the bird traverses more than a space of four 

 thousand five hundred feet in a minute, and that he can pro- 

 ceed twenty leagues in an hour. He may then easily proceed 

 at the rate of two hundred leagues a day, flying for only ten 

 hours. This supposes many intervals in the day, and the entire 

 night for repose. Swallows, and other birds of passage, may 

 thus proceed from our climate to the Line in less than seven or 

 eight days. M. Adanson has seen and caught, on the coast 

 of Senegal, swallows which arrived there the 9th of October, 

 that is, eight or nine days after their departure from Europe. 

 Pietro della Valle says that, in Persia, the carrier-pigeon makes 

 greater way in one day than a man on foot can in six. The 

 story of the falcon of Henry H. is well known, which, pursuing 

 with eagerness a smaller bustard at Fontainebleau, was taken 

 the following day at Malta, and recognised by the ring which 

 she bore. A falcon from the Canary Islands, sent to the Duke 

 of Lerma, returned from Andalusia to the Isle of Tenerifie in 

 sixteen hours, which is a passage of two hundred and fifty 

 leagues. Sir Hans Sloane assures us that, at Barbadoes, the 

 sea-gulls proceed in flocks to a distance of more than two 

 hundred miles, and return again the same day. A course like 

 this, of more than one hundred and thirty leagues, sufficiently 

 indicates the possibility of a voyage of two hundred ; and I 

 believe we may conclude, from the combination of all these 

 facts, that a bird of elevated flight can traverse every day four 

 or five times as much space as the most agile quadruped. 



" Every thing contributes to this facility of motion in the 

 bird. First, the feathers, whose substance is very light, whose 



