In applying the methods of rigid dynamics of three dimensions to the study of aeroplane motions, one of the first questions which had to be settled by myself and Mr. Harper in the preparation of “Stability in Aviation” was the choice of co–ordinate axes and the notation to be adopted for the various forces, couples and rates of variation of components of air resistance. Where, as in this case, the necessary symbols more than exhaust the ordinary alphabet, the problem is a difficult one, and it was therefore intended to insert a separate section explaining the advantages which rendered the choice adopted the only logically possible one.

Unfortunately, at the time when “ Stability in Aviation “ was published, very great doubts existed as to the practical utility of any such investigation except as a subject of academic study in orthodox mathematical circles, and the work of preparing the book in the face of obstacles, partly arising from opposition, had proved such a strain that any further discussions on the subject would have been incompatible with my academic duties.