318 REID— THE DISTRIBUTIOxN OF LAND 



equator, with the pole in Behring's sea ; that the southern hemi- 

 sphere contracted more than the northern and thus tended to in- 

 crease its rate of rotation, producing stresses which caused fractures 

 along the then equator. Aside from dynamical objections to such 

 a process, we note that Africa is not offset along the Mediterranean ; 

 only its southern part is offset. So that the explanation offered 

 does not apply to the conditions in attempts to explain. Here again 

 our predilection for the geographical north and south line brings its 

 influence to bear, and we think that the continents should naturally 

 lie north and south, and that any deviation from that direction needs 

 an explanation. But this is not so. In this particular case, how- 

 ever, the southern ends of -the three land projections lie all three 

 somewhat to the east of the northern parts, and this uniformity is 

 striking. But notice this : if these southern ends do not lie directly 

 south of the northern parts, two of them must be apparently dis- 

 placed in one direction ; the third might be displaced in the same or 

 in the opposite direction ; that it should happen to be in the same 

 direction is not remarkable. 



I think, therefore, we may agree that the main characteristics of 

 the distribution of land and water on the globe is contained in the 

 statement given in italics near the beginning of this paper. 



Why should we have a land hemisphere and a water hemisphere ? 

 The answer given by Herschel, about 60 years ago, is the true 

 answer, though to be sure, it only points the direction in which 

 further knowledge should be sought. Herschel's explanation was 

 that the center of mass of the earth and its center of figure do not 

 coincide. 



Let us examine this a little more closely. If the material of the 

 earth were distributed with perfect symmetry about the center of 

 mass the ocean would cover the whole earth to a uniform depth. 

 But if one hemisphere were slightly denser than the other the water 

 would be drawn to that side and make a deeper ocean there. 



How can we explain this lack of symmetry? We could easily 

 imagine that the earth, in whatever manner it may have developed, 

 might be lacking in symmetry sufficient to bring about the small 

 separation, about a mile and a half, between its center of mass and 



