Manuscripts/Mixed Material Article by Alexander Graham Bell, October 11, 1910
The balloon was changed from its original spherical form to a shape better adapted for propulsion
It has long been recognized by a growing school of thinkers, that an aerial vehicle, in order to cope with the wind, should be specifically heavier than the air through which it moves.
This position is supported by the fact that all of Nature's flying models, from the smallest insect to the largest bird, are specifically heavier than the air in which they fly most of them many hundreds of times heavier— and that none of them adopt the balloon principle in flight.
It is also significant in this connection that some of Santos Dumont's most celebrated exploits were accomplished with quite a small balloon, so ballasted as to sink in the air instead of rise. He was then enabled, under the influence of his motive power, to steer his balloon upwards without the expenditure of ballast, and to descend without the loss of gas.