294 DISCUSSIONS IN COSMOLOGY. 



are being denuded. It is therefore evident that sub- 

 aerial denudation is lowering the Equator as rapidly 

 as the sea-level is sinking from loss of rotation, and 

 that consequently we cannot infer from the present 

 form of our globe what was its form when it solidified. 

 In as far as tidal retardation can show to the con- 

 trary, its form, when solidification took place, may 

 have been as oblate as that of the planet Jupiter. 

 There is another circumstance which must be taken 

 into account. The lowering of the Equator, by the 

 transference of materials from the Equator to the 

 higher latitudes, must tend to increase the rate of 

 rotation, or, more properly, it must tend to lessen the 

 rate of tidal retardation. 



The argument may be shown to be inconclusive 

 from another consideration. The question as to whether 

 the earth's axis of rotation could ever have changed 

 to such an extent as to have affected the climate of 

 the Poles, a few years ago excited a good deal of 

 attention. The subject has been investigated with 

 great care by Professor Houghton,* Mr. George Dar- 

 win,-)- the Rev. J. F. Twisden,| and others, and the 

 general result arrived at may be expressed in the 

 words of Mr. G. Darwin : — " If the earth be quite rigid 

 no re-distribution of matter in new continents could 

 ever have caused the deviation of the Pole from its 

 present position to exceed the limit of about 3°." 



Mr. Darwin has shown that, in order to produce a 

 displacement of the pole to the extent of only 1° 46, 

 an area equal to one-twentieth of the entire surface of 

 the globe would have to be elevated to the height of 

 two miles. The entire continent of Europe elevated 



* Proc. Roy. Soc., vol. xxvi., p. 51. 

 f Proc. Roy. Soc. , vol. xxv. , p. 328. 

 % Paper- read before the Geological Society, February 21st, 1877. 



