e non-technical reason why the support of the machine becomes easier
as the speed increases is that the sustaining power of the atmosphere
increases with the resistance, and the speed with which the object is
moving increases this resistance. With a velocity of 12 miles an hour
the weight of the machine is practically reduced by 230 pounds. Thus, if
under a condition of absolute calm it were possible to sustain a weight
of 770 pounds, the same atmosphere would sustain a weight of 1,000
pounds moving at a speed of 12 miles an hour. This sustaining power
increases rapidly as the speed increases. While at 12 miles the
sustaining power is figured at 230 pounds, at 24 miles it is four times
as great, or 920 pounds.

Supporting Area of Birds.

One of the things which all producing aviators seek to copy is the
motive power of birds, particularly in their relation to the area of
support. Close investigation has established the fact that the larger
the bird the less is the relative area of support required to secure a
given result. This is shown in the following table:

Supporting
Weight Surface Horse area
Bird in lbs. in sq. feet power per lb.
Pigeon 1.00 0.7 0.012 0.7
Wild Goose 9.00 2.65 0.026 0.2833
Buzzard 5.00 5.03 0.015 1.06
Condor 17.00 9.85 0.043 0.57

So far as known the condor is the largest of modern birds. It has a wing
stretch of 10 feet from tip to tip, a supporting area of about 10 square
feet, and weighs 17 pounds. It. is capable of exerting perhaps 1-30
horsepower. (These figures are, of course, approximate.) Comparing the
condor with the buzzard with a wing stretch of 6 feet, supporting area
of 5 square feet, and a little over 1-100 horsepower, it may be seen
that, broadly speaking, the larger the bird the less surface area
(relatively) is needed for its support in the air.

Comparison With Aeroplanes.

If we compare the bird figures with those made possible by the
development of the aeroplane it will be readily seen that man has made a
wonderful advance in imitating the results produced by nature. Here are
the figures:

Supporting
Weight Surface Horse area
Machine in lbs.