It is safe to say that in no branch of applied science have the difficulties been greater or the process of development more rapid than in aeronautics. By far. the largest factor in the triumph of the aeroplane has been the improved internal combustion engine, a class of prime mover which, generating a maximum of power for a minimum of weight from concentrated fuel, is to-day such an outstanding engineering achievement as to arouse one's curiosity regarding its origin and development.

I cannot find better words, adequately to express my meaning, than those of John Farey (I) in his remarkable book, “On the Steam Engine,” published in 1827. Applying Farey's statement also to internal combustion as we know it, we might well say that in common with the steam engine, “It is an invention highly creditable to human genius and industry for it exhibits the most valuable application of philosophical principles to the arts of life and has produced greater and more general changes in the practice of mechanics than has ever been effected by any one invention in history.”

The basis for the calculation of wing vibration has been laid by the work of Küssner (I). The present paper describes a comparatively simple and yet accurate method of solving the two-dimensional problem in a manner suitable for the aircraft designer. In addition some of the results obtained by the new method are discussed.

In conjunction with H. Fingado, the author has described a graphical method for the rapid determination of the critical velocity of a two-dimensional wing without damping (see L.F.F., Vol. 13, No. 11 (20/11/36), pp. 374-387). The present paper presents a continuation of this work taking into account internal damping of the wing.