236 J, Evans on Geological Changes in the 
but had certain projecting portions, such as would be represen- 
ted in nature by continents and islands rising above the level of 
the sea. 
It is evident that so long as those continents and islands re- 
mained unultered in their condition and extent, the relative po- 
sition of the crust to the enclosed fluid nucleus would remain 
unaltered also. But supposing those projecting masses were 
either further upheaved from some internal cause, or worn down 
and ground away by the sea or by subaérial agency and deposi- 
ted elsewhere, it seems impossible but that the same effects must 
ensue as we see resulting upon the model from the elevation 
and depression of certain screws, and that the axis of rotation of 
the crust of the sphere would be changed in consequence of its 
having assumed a fresh position on its fluid nucleus, though the 
axis of the whole sphere might have retained its original direc- 
tion, or have altered from it only in the slightest degree. 
An irregular accumulation of ice at one or both of the poles, 
such as supposed by M. Adhémar, would act in the same manner 
as an elevation of the land; and even assuming that the whole 
land had disappeared from above the surface of the sea, yet if 
by marine currents the shallower parts of the universal ocean 
were deepened and the deeper parts filled up, there would, owing 
to the different specific gravity of the transported soil and the 
displaced water, be a disturbance in the equilibrium of the crust, 
and a consequent change in the position of its axis of rotation. 
Now if all this be true of a sphere, it will also, subject to cer- 
tain modifications, be true of a spheroid so slightly oblate as our 
obe. 
The main difference in the two cases is, that in a sphere the 
crust may assume any position upon the nucleus without any al- 
teration in its structure, while in the case of the movement of a 
spheroidal crust over a similar spheroidal nucleus, every por 
tion of its internal structure must ore or disturbed as 
the curvature at each point will be slightly altered. : 
__ The extent of the resistance to an alteration of position aris- 
ing from this cause will depend upon the‘oblateness of the 
‘ —— and the thickness and rigidity of the crust; while 
thicker the latter is, the less also will be the proportionate effect 
of such elevations, subsidences, and denudations as those with 
which we are acquainted. The question of friction upon the 
nucleus is also one that would have to be considered, as the 
internal matter though fluid might be viscous. 
t will of course be borne in mind that the elevations and de- 
pressions of the surface of the globe are not, on the theory now 
