90 
RAPIDITY OF FLIGHT. 
which was known by reference to a good map, in 
which the distances were well laid down. Such a 
rapid progress, We are aware, will scarcely he 
credited ; but 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. 
