1872.] Natural and Artificial Flight. 205 
It seems literally to float upon the air. No wing that is 
rigid in the anterior margin can twist and untwist during 
its action, and produce the figure-of-8 curves generated by 
the living wing. To produce the curves in question, the 
wing must be flexible, elastic, and capable of change of 
form in all its parts. The curves made by the artificial 
wave wing are largest when the vibration is slow, and least 
when the vibration is quick. In like manner, the air is 
thrown into large waves by the slow movement of a large 
wing, and into small waves by the rapid movement of a 
smaller wing. The size of the wing curves and air waves 
bear a fixed relation to each other, and both are dependent 
on the rapidity with which the wing is made to vibrate. 
This is proved by the fact that insects, in order to fly, require, 
as a rule, to drive their small wings with immense velocity. 
It is further proved by the fact that the small humming 
bird, in order to keep itself stationary before a flower, requires 
to oscillate its tiny wings with great rapidity, whereas the 
large humming bird (Patagona gigas), as was pointed out by 
Darwin, can attain the same object by flapping its large 
Wings with a very slow and powerful movement. In the 
larger birds the movements are slowed in proportion to the 
size, and more especially in proportion to the length of the 
wing, the cranes and vultures moving the wings very leisurely, 
and the large oceanic birds dispensing in a great measure 
with the flapping of the wings, and trusting for progression 
and support to the wings in the expanded position. This 
leads me to conclude that very large wings may be driven 
with a comparatively slow motion, a matter of very con- 
siderable importance in artificial flight secured by the flapping 
of wings.” 
“ The Artificial Wave Wing can be driven at any speed—it can 
make its own currents, or utilise existing ones.—One of the 
distinguishing features in the artificial wave wing is its 
adaptability. It can be driven slowly, or with astonishing 
rapidity. It has no dead points. It reverses instantly, and 
in such a manner as to dissipate neither time nor power. It 
alternately seizes and evades the air so as to extract a 
maximum amount of support with a minimum of slip, and 
a minimum expenditure of power. It supplies a degree 
of buoying and propelling power which is truly remarkable. 
Its buoying area is nearly equal to half a circle. It 
can act upon still air, and it can create and utilise its own 
currents. I proved this in the following manner :—I caused 
the wing to make a horizontal sweep from right to left over 
a candle; the wing rose steadily as a kite would, and after 
