VI PREFACE 



Moreover, it is to lie borne in mind that Mr. Langley's contribution to the 

 solution of the problem is not to be measured solely by what he himself accom 

 plished, important as thai is. He began his investigations at a time when not 

 only the general public but even the most progressive men of science thought of 

 mechanical flight only as a subject for ridicule, and both by his epoch-making 

 investigations in aerodynamics and by his own devotion to the subject of flight 

 itself lie helped to transform into a field of scientific inquiry what had before 

 been almost entirely in the possession of visionaries. 



The original plans for this publication provided for a third part, covering 

 the experimental data obtained in tests of curved surfaces and propellers. <>w 

 ing to the pressure of other matters on the writer, the preparation of this third 

 part is not yet complete and is reserved for later publication. 



Charles M. Manly. 

 New York City. 



