THE MULTIPLICATION OF EFFECTS. 451 



with the conditions. Oxidation, drought, wind, frost, rain, 

 glaciers, rivers, waves, and other denuding agents effect dis- 

 integrations that are determined in their amounts and quali- 

 ties by local circumstances. Acting upon a tract of granite, 

 such agents here work scarcely an appreciable effect; there 

 cause exfoliations of the surface, and a resulting heap of 

 debris and boulders; and elsewhere, after decomposing the 

 feldspar into a white clay, carry away this with the accom- 

 panying quartz and mica, and deposit them in separate beds, 

 fluviatile and marine. When the exposed land consists of 

 several unlike formations, sedimentary and igneous, changes 

 proportionately more heterogeneous are wrought. The for- 

 mations being disintegrable in different degrees, there fol- 

 lows an increased irregularity of surface. The areas 

 drained by different rivers being differently constituted, 

 these rivers cajry down to the sea unlike combinations of 

 ingredients; and so sundry new strata of distinct composi- 

 tion arise. And here indeed we may see very simply illus- 

 trated, the truth, that the heterogeneity of the effects in- 

 creases in a geometrical progression, with the heterogeneity 

 of the object acted upon. A continent of complex struc- 

 ture, presenting many strata irregularly distributed, raised 

 to various levels, tilted up at all angles, must, under the 

 same denuding agencies, give origin to immensely multi- 

 plied results : each district must be peculiarly modified ; each 

 river must carry down a distinct kind of detritus ; each de- 

 posit must be differently distributed by the entangled cur- 

 rents, tidal and other, which wash the contorted shores; and 

 every additional complication of surface must be the cause 

 of more than one additional consequence. But not to dwell 

 on these, let us for the fuller elucidation of this truth in 

 relation to the inorganic world, consider what would present- 

 ly follow from some extensive cosmical revolution say the 

 subsidence of Central America. The immediate results of 

 the disturbance would themselves be sufficiently complex. 

 Besides the numberless dislocations of strata, the ejections 



