232 J. Evans on Geological Changes in the 
mountain-mass could sensibly affect the position of the axis of 
rotation of the globe as a whole, and the general verdict was in 
the negative. 
Sir John Lubbock, however, in common «with other astrono- 
mers, ars to have regarded the earth as consisting of a soli 
nucleus with a body of water distributed over a portion of its 
surface; and there can be but little doubt that, on this assump- 
tion of the solidity of the earth, the usually received doctrines 
as to the general persistence of the direction of the poles are 
almost unassailable. 
Directly, however, that we argue from the contrary assump- 
tion that the solid portion of the globe consists of a compara- 
tively thin, but to some extent rigid crust with a fluid nucleus of 
incandescent mineral matter within, and that this crust, from va- 
rious causes, is liable to changes disturbing its equilibrium, It 
becomes apparent that such disturbances may lead, if not to 
a change in the position of the general axis of the globe, yet at 
_all events to a change in the relative positions of the solid crust 
and the fluid nucleus, and in consequence to a change in the axis 
of rotation, so far as the former is concerned. 
e existence in the center of the globe of a mass of matter 
fluid by heat, though accepted as a fact by many, if not most 
geologists, has no doubt been called in question by some, and 
well established that it is highly probable that at a certain depth 
such a degree of heat must be attained as would reduce all min- 
* Vol. v, p. 5. 
aaa Ria aA a SUS ce ca eae ae SS ds a a eee lL 20g 
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