The sailing flight of birds is the only form of flight which is carried on for some length of time without the expenditure of power.


The Romance of Aeronautics (1912)

Otto Lilienthal Quotes

The sailing flight of birds is the only form of flight which is carried on for some length of time without the expenditure of power.

The sailing flight of birds is the only form of flight which is carried on for some length of time without the expenditure of power.

The sailing flight of birds is the only form of flight which is carried on for some length of time without the expenditure of power.

The sailing flight of birds is the only form of flight which is carried on for some length of time without the expenditure of power.