W. B. Taylor — Crumpling of the Earth! s Crust. 263 



The expansion or stretching of the polar regions — referred 

 to, though probably less than Mr. Fisher would imagine, would 

 be attended with no dislocations, and would leave no traces. 

 A crust of ten or twenty miles depth pressing upon its interior 

 bed with a weight of five thousand or ten thousand tons to the 

 square foot, would flow (excepting its exterior film of a mile 

 or two), — on any relief of lateral pressure — as quickly and as 

 uniformly as so much plastic clay. 



To Mr. Fisher therefore belongs (so far as I am aware) the 

 credit of the first suggestion of a possible connection between 

 variation of oblateness and mountain-building ; — even though 

 by him discarded. He does indeed on the following page 

 recur to the topic ; and admitting that this variation ought to 

 have produced some appreciable effect, he suggests that this 

 apparent want of relation between the occurrence and the phe- 

 nomena, favors the idea of a change of latitudes. 



So strongly impressed is the writer with the inevitable opera- 

 tion and potency of this unquestioned retardation of rotation, 

 that were all traces of any differential action masked and 

 obliterated, he would still hold to it as the one efficient cause 

 (alone— as yet suggested) to account for the prominent con- 

 striction of the crust — displayed in every land. But the dif- 

 ferential traces of oblateness have not been obliterated ; — 

 masked though they may be to some extent, by other perturba- 

 tions. 



The suggestion of a change of axis, is one which will be 

 entertained by the physicist with extreme hesitancy and cau- 

 tion. Professor William Thomson indeed has stated that " the 

 axis of maximum inertia, and axis 'of rotation — always very 

 near one another — may have been in ancient times very far 

 from their present geographical position ; and may have grad- 

 ually shifted through 10, 20, 30, 40 or more degrees, without 

 at any time any perceptible sudden disturbance of either land 

 or water."* George Darwin also has admitted that if the 

 earth be not solid, "As in successive periods the continents 

 may have risen and fallen, the pole may have worked its way 

 in a devious course some 10° or 15° away from its geographical 

 position at consolidation ; or may have made an excursion of 

 smaller amount, and have returned to its old position. "f 



That under the continued stresses of precession and nuta- 

 tion — there should have been a slight slipping of the crust on 

 its fluid interior, is not improbable. The poles of the shell in 

 such case might describe a small spiral about the " axis of 

 maximum inertia," but could probably never diverge there- 

 from more than a ve^ few degrees. Nor could such gyration 



* Report Brit. Assoc, 1876, vol. xM, part ii, p. 11. 



f " On the Influence of Geological changes on the Earth's Asis of Rotation." 

 Phil. Trans. Roy. Soc, Nov. 23, 1876, vol. clxvii, p. 305. 



