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POPULAR SCIENCE MONTHLY. 



Diagram 1. Hargrave Box Kite. 



them hitched on one line. But Dr. Bell's object was great lifting 

 power in one kite and not in a team of kites. He realized that he was 



thwarted at the very outset 

 by an old law, which was 

 recently formulated by Dr. 

 Simon Newcomb and which 

 has made many believe that 

 the flying machine is impos- 

 sible without the discovery of 

 a new metal or a new force. 

 This law is that the weight of kites or machines built on exactly 

 the same model increases as the cube, when all the dimensions are 

 increased alike, while the supporting or wing surface increases as 

 the square. 



A Hargrave box kite two meters on a side weighs eight times as 

 much as one that is one meter on a side, but it has only four times as 

 much sustaining or wing surface; the weight is tripled, while the 

 wing surface is doubled; hence 

 as the size of a box kite is in- 

 creased a point soon comes 

 when the weight is so great 

 that the wing or support- 

 ing surface will not lift the 

 weight. 



Dr. Bell then set to work to see if he could not outwit this law by 

 devising a new form of kite which he could enlarge indefinitely without 

 the weight increasing faster than the wing surface. He saw that if he 

 could get a large kite by combining many small kites instead of by 

 increasing the dimensions of his model the weight would not 'increase 

 faster than the wing surface. He decided, therefore, to combine 

 many small cells into one large kite instead of using two large cells 

 each as big as a barn door. The Hargrave box cell however did not 

 lend itself to combination. Two box cells fly well, but when a number 

 of them are tied together they do not act with the 

 same harmony. A box cell is structurally weak in 

 all directions and requires a great deal of bracing 

 to keep it from being twisted in a strong breeze; 

 this bracing adds to the weight and makes head 

 resistance to the wind; the more cells combined 

 together, the more bracing required proportionally. 

 Furthermore, the cells must be grouped in two sets 

 at a distance from each other, and as the sets tend 

 to pull apart, the framework connecting the two sets has to be very 

 strong and heavy. As a result the experiments showed that neither 



Diagram 2. Triangular Cells. 



Diagram 3. Regu- 

 lar Tetrahedral 

 Winged Cell. 



