1888.] PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 367 



wiugs being rather large, the plane of rotation is constantly changing 

 in regard to its inclination with the horizon, and by this circumstance 

 causes the instrument to describe a series of complicated curves like 

 those of a large bird of prey before it settles at the feet of the thrower. 

 In general the initial plane of rotation must form an acute angle with 

 thcThorizou, which may increase to a right angle when the inclination 

 of the two wings is neariug its maximum. 



A very elaborate mathematical treatise on the boomerang has been 

 published by Prof. Werner Stille, Highland, 111. It is a communication 

 to Poggeudorf's Annalen der Physik, published at Berlin, Germany. 

 Mr. Stille starts from the supposition that the boomerang should form 

 a skew surface, a kind of screw. Accidentally I possessed an instru- 

 ment of a screw-like form. When properly thrown it screwed up all 

 right, but did not return. 



HOW TO THROW THE BOOMERANG. 



Take the boomerang with the full fist by one end, so that the flat side 

 of the instrument faces the ground, and then fling it away with out- 

 stretched arm, giving it at the same time a rotatory motion by a jerk 

 with the wrist. In the moment of leaving the hand the boomerang should 

 have an inclination toward the left, and its progressive motion should 

 be in an upward direction under a certain angle of elevation. The angle 

 of inclination to the left and the angle of elevation vary from one in- 

 strument to another, and have to be ascertained by some gentle trial 

 throws for any particular instrument before the thrower applies the 

 full power of his arm. The field for practice should be soft ground, free 

 of stones or other bard objects. Throw it against the wind, or half 

 against it. Do not practice when a hard breeze is blowing. 



I do not enlarge here on the different curves the boomerang describes 

 in accordance to its form and the manner of throwing, for it would 

 be unintelligible, unless illustrated by actual experiment. 



