45« THE POPULAR SCIENCE MONTHLY 



Each of these combinations is the starting point for a new individual. 

 It will be gray if there is a dominant G in the combination. Hence, 

 among the offspring there will be three gray and one white. The result 

 may be expressed by the formula 



GW • GW = 1GG + 2GW -f 1WW, 



which is corroborated by similar experiments of other investigators. 



In graphic statics, one of the most valuable branches of structural 

 engineering, may be found the reason for the peculiar distribution of 

 the substance in the upper portion of a thigh-bone along orthogonal 

 trajectories (Fig. 6 a). This is in analogy with the problem of a crane- 

 like structure, as diagrammatically shown in Fig. 6 b. It is well known 

 that the curves of maximum compression and tension in a strained 

 body form an orthogonal system, 9 and it seems natural that in order 

 to insure greatest strength, cell matter should be deposited according 

 to this system. 



An orthogonal system formed by the stream lines and lines of 

 greatest tension, which appear as lateral cracks and crevasses, is shown 

 in most glacial movements (Fig. 7). The directions of corresponding 

 stresses and sections upon which they act form an involutoric pencil 

 of rays. The case where the field is exclusively subject to tensions 

 only leads to elliptic involutions around all points. Every involutoric 

 pencil admits of a rectangular pair, corresponding to the maximum and 

 minimum stresses; tensions in this case. The effect of this condition 

 is shown in Fig. 8, representing the cracks of a mud-bed or on a heavily 

 varnished surface which is drying up. In this case only tensile normal 

 stresses act on the rectangular pair. One is a maximum, the other a 

 minimum. After a crack has formed, the maximal stress and strain 

 normal to the crack has been relieved, so that the former minimal 

 normal tension along the crack becomes now the maximum. The next 

 rupture will therefore be orthogonal to the first crack. The reason for 

 this peculiar configuration is thus found by the methods of projective 

 geometry. 10 



A great number of other examples from the realms of natural his- 

 tory might be added which all would give further evidence of the fact, 

 that the whole evolution of the inventive and creative human intellect 

 is reflected by the well-perceived phenomena of nature. 



By the laws of the universe the human mind is forced to repeat the 

 same logic conclusions, according to which the rest of the organic world 

 and nature in general manifest themselves. 



9 Ritter, "Graphische Statik," Vol. 1, pp. 128-134. 



10 Emch, "An Introduction to Projective Geometry and its Applications," 

 pp. 239-241, New York, 1905. 



