BOOMERANGS. 



gives to each of them, with practised skill, 

 a strong whirling spin, so that the gyroscopic 

 influence keeps them with their flat surfaces 

 in the same sloping plane, and they can slide 

 up the air, and down it again, with a steady 

 motion. 



This is the action of the simple boomerang, 

 with the edge which cuts the air evenly bevelled 



B 



D 



FlQ. 15. SCREW MOTION CAUSING RISE IN FLIGHT OF BOOMERANG 



on both sides all the way along. Boomerangs 

 are not all made on this simple plan, however. 

 If they are carefully examined, it will be seen 

 that some of them have the cutting edge nearer 

 to one side than to the other above or beneath 

 the plane of a central horizontal section. Thus 

 the one shown in Fig. 15 has a twist of such a 

 nature that at the end A the cutting edge is 

 nearly in a line with the upper surface, and 

 at the end B nearly in a line with the lower. 

 The reverse is the case with the opposite edges, 

 invisible in the figure, because at the back ; 



55 



