203 SUPP0S15D CHANGE OF AXIS OF EARTH'S CHUST. [Ch. XXXII. 



No 



Many 



mnst 



bnt their effect, says 



become 



feeble, althougli 



causing 



orio-inallj, when tlie fluidity of the globe was perfect, ' tbe 

 rise and fall of tbese ancient land tides could not have been 

 less tban from 13 to 16 feet.' Now, granting for a moment 

 that, these tides have become so feeble as to be incapable of 



tlie fissured sliell of the earth to be first uphfted and 

 then depressed every 6 hours, still may we not ask whether, 

 in every volcano during an eruption, the lava, which is sup- 

 posed to communicate with a great central ocean, would not 

 rise and fall sensibly, or whether, in a crater like Stromboli, 

 where there is always melted matter in a state of ebullition, 

 the ebbing and flowing of the liquid would not be constant ? 



earWs crust. — I alluded in 



Supposed change of axis < 

 Chapter XIII. to an ingenious paper,"^ replete with specula- 



tions of no ordinary 



Mr. Evans, in which he 

 climate on the surface 



snggcsted that former changes of 



mio^ht be connected with the sliding of a solid shell over an 



internal fluid nucleus. Grantmg 

 the equilibrium of the external 



moment 



mio 



■om 



the surface to another, or by the upheaval of new continents 

 and islands ; and Mr. Evans shows that, whenever matter is 

 abstracted from one part and added to another, the centri- 

 fuo"al force of the augmented extraneous matter would tend 

 to draw over the sliell towards the equator, or an opposite 

 effect Avould be produced if the surface was relieved of part 

 of its weight, in which case the lighter part would move 

 towards the pole. 



Newton 



fci 



•B 



probability of a shifting of the earth's axis of rotation, and 

 more recently Mr. Airy had among other a^ 

 out that the elevation of mountain chains at certain geolo- 

 gical periods, which had been proposed as causing an altera- 

 tion in the earth's centre of gravity, w^as an insignificant 

 cause, since the size of such mountain masses was very 

 minute when compared to the equatorial protuberance, 



* T. Evans, Royal Society rrocoedings, 18G6. 



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