TETBAHEDEAL KITES. 



137 



built in the laboratory. The experiments made with these cells have 

 given startling results: 



First. — A tetrahedral cell has astonishing strength even when com- 

 posed of very light wooden sticks. As Dr. Bell has expressed it: "It 

 is not simply braced in two directions in space like a triangle, but in three 

 directions like a solid. If I may coin a word, it possesses 'three-dimen- 

 sional' strength; not 'two-dimensional' strength like a triangle, or 

 ' one-dimensional ' strength like a rod. It is the skeleton of a solid, not 

 of a surface or a line."* 





Fig. 5. SlXTEEN-CELLED TETRAHEDRAL KITE. 



Second. — A large kite constructed of tetrahedral cells is as solid as a 

 small one, for it is likewise self-braced in all directions. 



Third. — A kite built of tetrahedral cells is an almost perfect flier; 

 it is steady in squalls, a good 'lifter' and flj^s almost directly over- 

 head. Tetrahedral cells when combined do not interfere with each 

 other in the least or hurt each other's flying ability as box or triangular 

 cells do when combined. 



* ' The Tetrahedral Principle in Kite Structure. 

 Bell. National GeograpJiic Magazine, June, 1903. 



By Dr. Alexander Graham 



