THE AGE OF THE EARTH AS AN ABODE FITTED FOR LIFE. 237 



the delayed central concentration left some notable part of the accel- 

 eration to be gained during the period of geological history, and if, at 

 the same time, a slow aggregation of the moon delayed its effectual 

 tidal influence upon the earth and the reciprocal influence of the earth 

 upon it, the whole history may be notably affected in the direction at 

 once of less maximum speed and of less retardation; i. e., of more 

 near approach to uniformity. 



If we turn to the geological data that bear on the question of former 

 high rotation and subsequent retardation, we find ample support for 

 profound skepticism regarding the applicability of the tidal argument. 

 As pointed out by Lord Kelvin, if the rotation of the earth were once 

 notably greater than at present it should have resulted in an oblateness 

 of the spheroid such that the equatorial regions would now be all dry 

 land, unless the body af the earth were deformed to correspond to the 

 slackening rotation in an almost perfect manner. But there is not the 

 slightest evidence in the configuration of the earth of such an equa- 

 torial land tract. The equatorial belt is notably oceanic rather than 

 otherwise. Reciprocall}", there should have been, with the gradual 

 slackening of the earth's rotation, an accumulation of the oceanic waters 

 about the poles, but there is no geological evidence of such an accu- 

 mulation in any appreciable degree. In the arctic regions, as exem- 

 plified in Greenland, Spitzbergen, and the arctic islands of America, 

 there are ancient shallow-water deposits, which lie both above and below 

 the present oceanic level. These deposits range throughout the Paleo- 

 zoic and represent in some less degree both the Mesozoic and Cenozoic 

 eras. The nature of these shallow-water deposits is such that the}^ 

 can not have been formed at great depths below the oceanic surface, 

 so that, with the allowance of a few hundred feet, it is possible to locate 

 the ancient horizons relative to the crust of the earth at most or all of 

 these periods. From these it may be inferred with great confidence 

 that the ancient ocean surface in the arctic regions was in numerous 

 stages of Paleozoic, Mesozoic, and Cenozoic eras not notably different 

 from that of to-day. The facts even justify the seemingly extravagant 

 statement that at several stages in geological history, early and late, 

 the svirface of the ancient ocean did not vary a foot from that of the 

 present, since it must have passed both above and below the present 

 horizon repeatedly during the earth's history. Geological evidence, 

 therefore, intv'rpreted on its own legitimate basis, seems to lend no 

 appreciable suoport to any theory that postulates a high speed of rota- 

 tion for the early earth or a low speed of rotation for the present 

 earth, unless that hypothesis is correlated with the assumption of an 

 almost perfect adjustability of the form of the earth to the changing 

 rotation, in which case the argument of Lord Kelvin set forth on page 

 670 (Science, May 12) stands confessedly for naught. 



If we postulate a slow accretion of the earth and of the moon alike, 



