Page:Popular Science Monthly Volume 64.djvu/141

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built in the laboratory. The experiments made with these cells have given startling results:

First.—A tetrahedral cell has astonishing strength even when composed 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-dimensional' 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."[1]

PSM V64 D141 Sixteen celled tetrahedral kite.png

Fig. 5. Sixteen-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 flys almost directly overhead. 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.

  1. 'The Tetrahedral Principle in Kite Structure.' By Dr. Alexander Graham Bell. National Geographic Magazine, June, 1903.