

48 THE FIGURE OF THE EARTH 



figuration, which was one of equilibrium for the com- 

 pressibility obtaining at the moment of solidification, 

 would not remain so after the compressibility and 

 rigidity of the material had increased by cooling. If 

 we suppose the earth to cool in an asymmetrical con- 

 figuration the stresses set up will soon become very great. 

 In fact, Professor Darwin has shown that the stresses 

 which would be produced by the weights of our conti- 

 nents in an earth initially homogeneous (i.e., by an 

 irregularity of less than a thousandth part of the radius) 

 would be so great that the material would be near the 

 breaking-point. 



" We must therefore suppose that, as the earth cools 

 and the elastic constants change, there will be a series of 

 ruptures resulting from the stresses set up in the interior. 

 The configuration will become approximately spherical 

 (spheroidal if rotation be taken into account) as soon 

 as the point of bifurcation is passed. 



"The fact that the ultimate configuration is reached 

 only as the result of a long succession of ruptures puts 

 the whole question outside the range of exact mathemati- 

 cal treatment. We can, however, see that the final con- 

 figuration (disregarding rotation) will probably be not 

 quite spherical, but will retain traces of the initial asym- 

 metrical configuration . . . when the final stage is 

 reached (the) surface would not be quite an equipoten- 

 tial, and the centre of gravity would not quite coincide 

 with the centre of figure. If water is placed on the sur- 

 face of a planet of this kind it will form a circular sea, of 

 which the centre will be on the axis of harmonics, while 

 the dry land will form a spherical cap." 



Thus, then, the astronomer prepares for us an ocean 

 bed by forces incomparably more powerful than those 

 differences of atmospheric pressure, to which, in default 

 of this explanation, I have had recourse. But those con- 



