518 



BOOMERANGS. 



For a figure of 8 we should require less rounding, or we might 

 give more spin in throwing, and aim a little uphill, with rather less 



Fig. 10.— Plan. 



Fig. 11.— Elevation through G F. 



than a right angle. There are so many elements capable of variation 

 that nothing but experience can teach how to get the best results with 

 any particular boomerang. 



The most complex path that the author has succeeded 

 in effecting is that of tigs. 10 and 11. But it is certain 

 that these fall far short of what is done by skillful natives 

 of Australia. 



If the angle between the arms is increased and the 

 twist and rounding unaltered, the angular velocity (1) is 

 increased, and it becomes easier to make a second loop 

 behind than in front. If the angle exceeds 150° the angu- 

 lar velocity of the first kind is so large that it is very 

 hard to get a return at all. 



When the twist is left-handed and the angle large we 

 have a specimen of the second type (tig. 3), and it must be 

 thrown with the more rounded side uppermost and the plane of rota- 

 tion inclined at between 30° and 60° to the horizontal (i. e., 30°<#<60 o ); 

 the angle of projection (i. e., inclina- 

 tion to the horizon of the initial veloc- 

 ity of translation) must be comparable 

 with 45°. 



The uphill path is nearly straight 

 until the forward velocity becomes 

 small; the projectile then returns along 

 a track close to that of the ascent (figs. 

 V2 and 13). 



Fig. 12.— Plan 



NON RETURNING FLIGHTS. 



Fig. 13.— Elevation through A C. 



A good boomerang of the second 

 type will travel an immense distance in a nearly straight line if prop- 

 erly thrown. The motion should resemble that of an aeroplane or 

 flying machine; the plane of rotation must remain nearly horizontal, 



