1888.] PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 365 



The boomerang, according to those specimens, consists of two sym- 

 metrical wings ; that is, symmetrical in regard to a plane by which these 

 two wings are joined. 



Fig. 3. 



The angle of the lines D C and E C, which pass through the center 

 C of line A B, and also through the centers D and E of the ends, I will 

 call the " angle of the boomerang." The size of this angle varies be- 

 tween wide limits. My instruments have angles from 100 up to 140 

 degrees, and yet all these different instruments can be made to work 

 properly ; that is, boomerang-fashion. Perhaps this circumstance is the 

 principal reason that the boomerang is at all popular in Australia. For 

 if the efficacy of this instrument were limited by an angle of a fixed 

 size, how few branches of trees would be found suitable. However, 

 certain sizes of angle a re more convenient to the thrower than others, 

 and I found that angles from 116 to 120 degrees are very conven- 

 ient. The relation between thickness, breadth, and length, absolute 

 weight of the boomerang, and specific gravity of its material can very 

 probably be expressed by numbers, but they are unknown, and evidently 

 vary also between extended limits. The instruments sent to the Smith- 

 sonian have very nearly the numbers 1 : 6 : 36 ; that is, the maximum 

 breadth is six times the. maximum thickness, and the length of each 

 wing is six times its maximum breadth. But writing 5i instead of 6 in 

 the above proportion, so that the latter would be 1 : 5i : (oh) 2 , would 

 be just as near the ideal numerical relations. I am inclined to believe 

 that these numbers are influenced by the specific gravity of the mate- 

 rial. That the above proportion does not entirely govern the geometri- 

 cal form of the boomeiang, I conclude from the fact that after breaking 

 part of the wing (say one-fourth of its length) off from a good instru- 

 ment, I did not notice any material loss of its good quality. 



Lubbock has given the measurements of one boomeraug and Profess- 

 or Erdman at Berlin, Germany, the dimensions of three others. These 

 measurements may serve as a guide to a superficial construction of the 

 boomerang; but these writers do not mention, as it seems to me, the 

 essential point of a good boomerang: "the angle of inclination of the 

 two wings." The wings of my instruments have each a plane side. 



