II. On boomerangs

The attempts that have hitherto been made to explain the flight of a boomerang have in general been of a somewhat fanciful nature. Exception must be made in the case of such papers as those of Werner Stille, “Versuche und Rechnungen zur Bestimmung der Batmen des Bumerangs” (Poggen- dorff, 'Annalen der Physik,’ Bd. 147, 1872), and of Edmund Gerlach, “ Ableitung gewisser Bewegungsformen geworfener Scheiben aus dem Luftwiderstandsgesetze” (‘Zeitschrift des Deutschen Yereins zur Förderung der Luftschifffahrt,’ Heft 3, 1886). In the latter, which is the most noticeable contribution to the subject with which I am acquainted, the author gives an explanation in general terms of some of the effects of the air-resistance upon a symmetrical boomerang : he introduces, however, no analytical treatment of the dynamics of the rotating body and neglects entirely all consequences of the important deviations from symmetry which I have subsequently described as “ twisting” and “ rounding.” Without one of these a return flight is, I believe, impossible.