Aërial Navigation: A Popular Treatise on the Growth of Air Craft and on Aëronautical Meteorology — John Shaqi
Aërial Navigation: A Popular Treatise on the Growth of Air Craft and on Aëronautical MeteorologyZahm, Albert Francis
History
Aërial Navigation: A Popular Treatise on the Growth of Air Craft and on Aëronautical Meteorology
Zahm, Albert Francis
Aeronautics; Meteorology
Dissolved apace, and soon began to run:
The youth in vain his melting pinion shakes,
His feathers gone, no longer air he takes:
“Oh! father, father!” as he strove to cry,
Down to the sea he tumbled from on high,
And found his fate; yet still subsists by Fame,
Among those waters that retain his name.
The Father, now no more a father, cries:
“Ho, Icarus! where are you?” as he flies;
“Where shall I seek my boy?” he cries again,
And saw his feathers scatter’d on the main;
Then cursed his art; and funeral rites conferr’d
Naming the country from the youth interr’d.
How tender and apprehensive that gentleman’s farewell, compared with
the modern vogue in like circumstances! Of the two Americans at Berlin
who fell four thousand feet in a balloon, it is not recorded that they
either kissed or wept.[2] But some Teutonic Ovid may yet adorn the tale
with quaint embellishments.
Taking more serious note of Daedalus, it will be observed that he
has had few imitators. It is because he never really flew, and no
one else can fly, in such manner. That is to say, no man can achieve
practical flight on wings actuated by his own muscular power. It may be
physically possible for an athlete putting forth herculean energy for
a few seconds to sustain himself on wings of enormous spread; but in
every lightest zephyr he would be as helpless as a thistle seed.
The actual area of wing required for a man of given weight and power
may be roughly estimated; at least its lower limit of size can be
determined. Lord Rayleigh,[3] on purely theoretical ground, has
computed that a man operating a screw propeller 280 feet in diameter,
moving without frictional loss, could sustain his weight for a period
of eight hours a day at a comfortable rate of work. But that estimate
does not include the weight of the propeller. By exerting ten times his
normal power the man could support his weight with a 28-foot propeller.
The physical basis of the computation is the same for every type of
flyer, whether bird, man, or machine. Its weight must be sustained by
hurling the air downward. The humming bird in its aërial pause, the bee
floating beside a blossom, rests on a down-driven column of air. The
home-gliding eagle at dusk may encounter a medium in stillest repose,
but he leaves behind him a down-flowing wake, viewless, maybe, but none
the less real. In all cases the downward impulse per second given to
the air must equal the weight supported by its reaction. If the wings
be very extensive a proportionate mass of air may be struck down, and
yield support with so much the less exertion.
Public-domain text, read in full here on John Shaqi.
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