226 The National Geographic Magazine 



hedral kite, or kite having the form of 

 a tetrahedron. 



The kite shown in figure 14 is com- 

 posed of four winged cells of the regular 

 tetrahedron variety (see Fig. 10), con- 

 nected together at the corners. Four 

 kites like figure 14 are combined in fig- 

 ure 15, and four kites like figure 15 in 

 figure 16 (at U). 



Upon this mode of construction an 

 empty space of octahedral form is left 

 in the middle of the kite, which seems 

 to have the same function as the space 

 between the two cells of the Hargrave 

 box kite. The tetrahedral kites that 

 have the largest central spaces preserve 

 their equilibrium best in the air. 



reason why this principle of combination 

 should not be applied indefinitely so as 

 to form still greater combinations. 



The weight relatively to the wing- 

 surface remains the same, however large 

 the compound kite may be. 



The four-celled kite B, for example, 

 weighs four times as much as one cell 

 and has four times as much wing-sur- 

 face, the 16-celled kite C has sixteen 

 times as much weight and sixteen times 

 as much-wing surface, and the 64-celled 

 kite D has sixty- four times as much 

 weight and sixty-four times as much 

 wing-surface. The ratio of weight to 



FIG. T4— FOUR-CELLED TETRAHEDRAL KITE 



The most convenient place for the 

 attachment of the flying cord is the ex- 

 treme point of the bow. If the cord is 

 attached to points successively further 

 back on the keel, the flying cord makes 

 a greater and greater angle with the 

 horizon, and the kite flies more nearly 

 overhead; but it is not advisable to carry 

 the point of attachment as far back as 

 the middle of the keel. A good place 

 for high flights is a point half-way be- 

 tween the bow^and the middle of the 

 keel. 



In the tetrahedral kites shown in the 

 plate (Fig. 16) the compound structure 

 has itself in each case the form of the 

 regular tetrahedron, and there is no 



fig. 15- 



SIXTEEN-CELLED TETRAHEDRAL 

 KITE 



surface, therefore, is the same for the 

 larger kites as for the smaller. 



This, at first sight, appears to be some- 

 what inconsistent with certain mathe- 

 matical conclusions announced by Prof. 

 Simon Newcomb in an article entitled 

 "Is the Air-ship Coming," published 

 in McClure's Magazine for September, 

 1901 — conclusions which led him to be- 

 lieve that " the construction of an aerial 

 vehicle which could carry even a single 

 man from place to place at pleasure re- 

 quires the discovery of some new metal 

 or some new force. ' ' 



The process of reasoning by which 

 Professor Newcomb arrived at this re- 



