228 
THE BEAUTIFUL LADDER. 
reproduced for our instruction. He says : ‘ The 
humming-birds are perhaps the most remark¬ 
able examples in the world of the machinery 
of flight. The power of poising themselves in 
the air—remaining absolutely stationary whilst 
they search the blossoms for insects—is a power 
essential to their life. It is a power, accord¬ 
ingly, which is enjoyed by them in the high¬ 
est perfection. When they intend progressive 
flight, it is effected with such velocity as to 
elude the eye. The action of the wing in all 
these cases is far too rapid to enable the ob¬ 
server to detect the exact difference between 
the kind of motion which keeps the bird at 
absolute rest in the air and that which car¬ 
ries it alor^ with such velocity. But there can 
be no doubt that the change is one from a short, 
quick stroke, delivered obliquely forward, to a 
full stroke, more slow, but delivered perpendic¬ 
ularly. This corresponds with the account 
given by that most accurate ornithological ob¬ 
server, Mr. Gould. He says: “ When poised 
before any object this motion of the wing is so 
rapidly performed that it is impossible for the 
eye to follow each stroke, and a hazy semicir¬ 
cle of indistinctness on each side of the bird is 
