Position of the Axis of the Earth’s Crust. 233 
eral matter with which we are acquainted into a state of fusion. 
When once this point was attained, it seems probable that there 
would be no very great variation in the temperature of the in- 
ternal mass ; but whether the whole is in one uniform state of 
fluidity, or whether there is a mass of solid matter in the center 
of the fluid nucleus, are questions which do not affect the hy- 
pothesis about to be considered. 
h 
m e accounted for on the chemical theory, which has re- 
ceived the support, among others, of Sir Charles Lyell. But 
The supposition that the gradual oscillations of the surface of 
the earth, of which we have evidence all over the world as hav- 
ing taken place ever since the formation of the earliest known 
_ Strata up to the present. time, are due to the alternate inflation 
by gas and the subsequent depletion of certain vast bladdery 
Cavities in the crust of the earth, can hardly be generally ac- 
cepted 
to each other of a solid crust anda fluid nucleus in rotation 
together is that of a sphere, de 
Let AC BD bea halee sphere composed of solid materials’ 
and of perfectly uniform thickness and density, and let it be 
filled with the fluid matter E, over which the solid shell can 
eely move, and let the whole be in uniform rotation about an 
* 2nd edit., 1858, vol. i, p. 36. 
