1872.] Natural and Artificial Flight. 199 
wing glide into each other when the wing is in motion, so 
the one pulsation merges into the other by a series of inter- 
mediate and lesser pulsations. 
The longitudinal and lateral pulsations occasioned by 
the wing in action may be fitly represented by waved tracks 
running at right angles to each other, the longitudinal 
waved track being the more distinct.” 
“ Analogy between the Wing in Motion and the Sounding of 
Sonorous Bodies. —It is a remarkable circumstance that 
the undulation or wave made by the wing when the insect 
and bird are fixed or hovering before an object, and when 
they are progressing, corresponds in a marked manner with 
the track described by the stationary and progressive waves 
in fluids,* and likewise with the waves of sound.t This 
coincidence would seem to argue an intimate relation 
between the instrument and the medium on which it is 
destined to operate—the wing acting in those very curves 
into which the atmosphere is naturally thrown in the trans- 
mission of sound, in order, as appears to me, to secure the 
maximum of progression with the minimum of slip. Can 
it be that the animate and inanimate world reciprocate, and 
that animal bodies are made to impress the inanimate in 
precisely the same manner as the inanimate impress each 
other? This much seems certain :—The wind communicates 
to the water similar impulses to those communicated to it 
by the fish in swimming; and the wing in its vibrations 
impinges upon the air as an ordinary sound would. The 
extremities of quadrupeds, moreover, describe spiral tracks 
on the land when walking and running; so that one great 
law would seem to determine the course of the insect 
in the air, the fish in the water, and the quadruped on the 
land.” 
“Weight contributes to Horizontal Flight.—That the weight 
of the body plays an important part in the production of 
flight may be proved by a very simple experiment. If two 
primary feathers are fixed into an ordinary cork, and the 
apparatus is allowed to drop from a height, the cork does 
not fall vertically downwards, but downwards and forwards, 
and for the following reasons. The feathers are twisted 
flexible inclined planes, which arch in an upward direction. 
They are, in fact, true wings in the sense that an insect wing 
in one piece is a true wing. When dragged downwards by 
the cork, which would, if left to itself, fall vertically, they 
* Handbook of Natural Philosophy. Vol. on Ele@ricity, Magnetism, and 
Acoustics, pp. 366-7. By Dr. Larpner. London, 1863. 
t+ Op. cit., pp. 378, 379, 380. 
