AroiST 14. 1903.] 



SCIENCE. 



207 



character shown at B, in which the frame- 

 work forms the outline of a tetrahedron. 

 In this case the aeroplanes are triangular, 

 and the whole arrangement is strongly 

 suggestive of a pair of bird's wings raised 

 at an angle and connected together tip to 

 tip by a cross bar. 



■'In the tetrahedral kites, shown in the 

 plate (Figs. 4 and 5), the compound struc- 

 ture has, itself, in each case the form of the 

 regular tetrahedron, and there is no i-eason 

 why this principle of combination should 

 not be applied indefinitely so as to form 



of some new metal or some new force.' 

 The process of i asoning by which Pro- 

 fessor Newcomb arrived at this remarkable 

 result is undoubtedly correct. His con- 

 clusion, however, is open to question be- 

 cause he has drawn a general conclusion 

 from restricted premises. 



"He says: 'Let us make two flying ma- 

 chines exactly alike, only make one on 

 double the scale of the other in all of its 

 dimensions. We all know that the volume, 

 and therefore the weight, of two similar 

 bodies are proportional to the cubes of their 



Fig. 4. Fonr-oelled tetrahedral kite. 



still greater combinations. The weight 

 relative to the wing-surface remains the 

 same, however large the compound kite 

 may be. The four-celled kite (Fig. 4), for 

 example, weighs four times as much as 

 one cell and has four times as much wing 

 surface. 



' ' This, at first sight, appears to be some- 

 what inconsistent w'ith certain mathemat- 

 ical conclusions announced by Professor 

 Simon Newcomb in an article entitled, 'Is 

 the Air-ship Coming"' published in Mc- 

 C'lure's Magazine for September, 1901— 

 conclusions which led him to believe that 

 ' the construction of an aerial vehicle which 

 would carry even a single man from place 

 to place at pleasure requires the discovery 



Fig. 5. Sixteen-celled tetrahedral kite. 



dimensions. The cube of two is eight: 

 hence the larger machine will have eight 

 times the weight of the other. But sur- 

 faces are as the square of the dimensions. . 

 The square of two is four. The heavier 

 machine will therefore expose only four 

 times the wing surface to the air, and so 

 will have a distinct disadvantage in the 

 ratio of efficiency to weight. 



"But Professor Newcomb "s results are 

 probably only true when restricted to his 

 premises. For models exactly alike, only 

 (hi/fering in the scale of their dimensions, 

 his conclusions are undoubtedly sound; 

 but where large kites are formed by the 

 multiplication of smaller kites into a cellu- 

 lar structure the results are verv different." 



