204 The Field of Geology— McGee. 



inequality in altitude between ocean bottom and land surface, and 

 that the difference in rate of secular cooling similarly appears in- 

 adequate alone to explain the aggregate of epeirogenic movement; 

 and herein lies the supposed weakness of Faye's hypothesis. Be it 

 noted, however, that the cause has not only been in operation 

 throughout geologic time, but has produced cumulative and thereby 

 greatly multiplied effects. The direct and indirect consequences 

 of an initial inequality in temperature of the earth's crust are 

 complex and far-reaching, though none the less obvious. If a 

 slight irregularity in a shoal sea bottom, sufficient to deepen the 

 waters on the one hand and expose the rocks on the other baud, be 

 given, it is evident (1) that the sea bottom will be chilled and the 

 exposed rocks warmed, producing (2) contractional shortening of 

 the sea bottom radius and deepening of the basin, together with 

 expansional elongation of the land radius and elevation of the 

 nascent land, and at the same time (8) condensation of the sea 

 bottom strata and lightening of the land strata accompanied by 

 further sinking of the former and rise of the latter in isostatic ad- 

 justment. It is equally evident that these movements will be fol- 

 lowed by (4) desiccation, oxidation, disintegration, and relief from 

 pressure, and thus further lightening, of the land strata; and 

 eventually by (5) erosion of the exposed rocks and deposition of 

 their detritus in less compact condition about the land periphery, 

 thereby farther diminishing the mean density o£ the growing 

 land, and consequently (6) still further elevation of the land and 

 relative depression of the sea basin. It is evident also (7) that each 

 of these consequent movements must co-operate with the initial 

 one in deforming the earth's shell, (8) that each additional defor- 

 mation must (within certain distant limits) increase the difference 

 in rate of refrigeration both directly and through differentiation 

 and consequent levitation of the nascent land, to be followed in turn 

 by (9) renewed deformation. Whether these cumulative tendencies 

 are quantitavel}? adequate to produce the observed difference in 

 density and altitude of ocean basins and continents and the sum of 

 the antecedent deformation of the earth cannot be determined at 

 least until the researches of Woodward upon the rates and effects of 

 secular of cooling of the earth have borne fruit; but certainly there 

 is here a veritable, and as viewed from the standpoint of the geol- 

 ogist apparently a sufficient cause of antecedent diastatic movement. 

 If the cause be adequate, world-history becomes simple and in- 



