IIAPIDITY OF FLIGHT. 91 



which was known hy reference to a good map, in 

 which the distances were well laid down. Such a 

 rapid progress, we are aware, will scarcely be 

 credited; hut a celebrated naturalist, in speaking of 

 the large white Fishing Eagle of North America, 

 gives reasons for suspecting that its speed is still 

 greater: he says that, from an immense height, on 

 perceiving their prey, they glide downwards with 

 such rapidity as to cause a mighty rushing sound, 

 not unlike that produced by a violent gust of wind 

 passing amongst the branches of trees; and that the 

 fall of this bird, enormous as it is, can on such 

 occasions be scarcely followed by the eye*. Those 

 who ride over commons or fine turf, may often have 

 witnessed a quickness of flight, probably not much 

 inferior to these Eagles; for they will, even at 

 their fullest speed on the fleetest horse, have seen 

 Swallows skimming in all directions, pursuing the 

 small insects which the horse puts up in his course 

 over the grass, sometimes leisurely keeping at an 

 equal pace, then shooting ahead, and not unfre- 

 quently actually flying round the rider in wide 

 circles, with an ease and facility, betraying neither 

 effort nor labour in so doing. 



The flight of the common Swallow has been com- 

 puted at 90 miles, but the Swift has been conjectured 

 to be nearly 180 miles per hour. We can scarcely, 

 indeed, calculate or limit the speed which can be 

 produced by the effort of a wing's vibrations. That 

 a small insect can with ease accomplish forty or fifty 

 miles an hour, and probably much more, we know 

 to be a fact, from our own experience on the Liver- 

 * Audubon. 



