THE MULTIPLICATION OF EFFECTS. 449 



them to be. Thus, leaving out of view other modifying 

 forces, we see what immense heterogeneity of surface arises 

 from the one cause, loss of heat a heterogeneity which the 

 telescope shows us to be paralleled on the Moon, where aque- 

 ous and atmospheric agencies have been absent. But 

 we have yet to notice another kind of heterogeneity of 

 surface, similarly and simultaneously caused. While the 

 Earth's crust was still thin, the ridges produced by its con- 

 traction must not only have been small, but the tracts be- 

 tween them must have rested with comparative smoothness 

 on the subjacent liquid spheroid; and the water in those arc- 

 tic and antarctic regions where it first condensed, must have 

 been evenly distributed. But as fast as the crust- grew 

 thicker and gained corresponding strength, the lines of frac- 

 ture from time to time caused in it, necessarily occurred at 

 greater distances apart; the intermediate surfaces followed 

 the contracting nucleus with less uniformity ; and there con- 

 sequently resulted larger areas of land and water. If any 

 one, after wrapping an orange in wet tissue paper, and ob- 

 serving both how small are the wrinkles and how evenly 

 the intervening spaces lie on the surface of the orange, will 

 then wrap it in thick cartridge-paper, and note both the 

 greater height of the ridges and the larger spaces through- 

 out which the paper does not touch the orange, he will real- 

 ize the fact, that as the Earth's solid envelope thickened, the 

 areas of elevation and depression became greater. In place 

 of islands more or less homogeneously scattered over an 

 all-embracing sea, there must have gradually arisen hetero- 

 geneous arrangements of continent and ocean, such as we 

 now know. This double change in the extent and 

 in the elevation of the lands, involved yet another species of 

 heterogeneity that of coast-line. A tolerably even sur- 

 face raised out of the ocean will have a simple, regular sea- 

 margin; but a surface varied by table-lands and intersected 

 by mountain-chains, will, when raised out of the ocean, have 

 an outline extremely irregular, alike in its leading features 



