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Ch. XXXIL] PAETIAL FLUIDITY OF EAETII'S CKUST. 



209 



wliicli lie sajs is a mass of matter 25,000 miles' long, 

 6,000 miles broad, and 13 miles 



sug2'ests tliat the 



deep. 



Bnt Mr. Evans 



axis of rotation of the nucleus might 



remain unchanged, while a solid shell not more, perhaps, 



than 25 miles in thickness might have its axis of rotation 



altered. To this hypothesis there are several objections : 



First, in all geological times, the transfer of sediment has 



-I !!• 1 i in ^.^ ._ 



& 



om 



but also from lower to higher. There is the like tendency in 

 the various elevations and depressions of land simultane- 

 ously in progress to balance each other. It is only the 

 excess of alteration in one direction that can be available as 

 a disturbing cause, and we can hardly imagine this excess 

 to be important enough to cause a sensible change in the 

 axis of rotation even of the external shell, such as mio-ht 

 explain the altered climate of the same country in successive 

 geological periods. 



Secondly, a greater difficulty arises out of the fact that 

 the earth is a spheroid and not a perfect sphere, since it 

 becomes necessary to imagine the fluidity of the nucleus to 

 be so perfect as to allow the shell to slide freely over it. If 

 the lower or inner surface of the envelope be irregular in 

 shape, or if it be even viscous in part, great redstance 

 would be ofiPered to any change in its position. Its freedom 

 of motion would be checked by its not fitting the nucleus, 

 let its change of position be ever so slight, and this chan-e 



most 



Partial fluidity of 

 volcanic phenomena. 



mass 



the earth's crust most consistent with 



, . , ^^ ^^st not be forgotten that the 



l'?;i-!!' Z!?"''^^!'''''' '^'^^ ^^ ^^^^^ respecting the original 



of 



n . -J.J ' ^^^^ ^^>^^K^yyu±±j.^ Lilt; UXiyj 



nuidity of the planet, and the gradual consolidation oi 



ts external shell, belong to a period when theoretical ideas 



foZl ''!*''^^"^^*^ ^' *« ^^^ relative age of the crystalline 



sta W '''' 1 ^^"* '^'^^ ^^^^^^ ^* ™^^^^ ^itl^ the present 

 ^r^Jl '''''" ™^l*^^ge- It was formerly imagined that all 

 g amte was of very high antiquity, and that rocks such as 

 to tbl "".'f-'^^i^t, and clay slate, were also anterior in date 

 tne existence of organic beings on a habitable surface. It 



VOL. II, 



P 



i 



