234 J, Evans on Geological Changes in the 
axis FG, the line CD representing the equator. It is evident 
that in such a case, the hollow sphere being in perfect equilib- 
at H would gradually draw over 
the shell toward D until, by slid- 
ing over the nucleus, it attained 
its greatest possible distance from 
the center of revolution by ar- 
riving at the equator. The resultant effect would be that though 
the whole sphere continued to revolve around an axis as nearly 
as possible in the line FG, yet the position of the pole of the 
hollow shell would have been changed by 45°, as by the passage 
f H to the equator the points I and would have been 
brought to the poles by spirals constantly decreasing in diameter, 
while A and B, by spirals constantly increasing, would have at 
come to describe circles midway between the poles and the 
G 
equator. ’ : ; 
The axis of rotation of the hollow sphere and that of its fluid 
contents would now again coincide, and would continue to do s0 
perpetually unless some fresh disturbance in the equilibrium of 
the shell took place. 
If instead of the addition of fresh matter at H we had sup- 
an excavation or removal of some portion of the shell, 4 
' movement in the axis of rotation of the shell would also have 
ensued, since from the diminished centrifugal force of that por- 
tion of the hollow sphere where the excavation had taken place, 
it would no longer equipoise the corresponding portion on the 
opposite side at I, and the excavated spot would eventually find 
its way to the pole. 
In order more clearly to exhibit these effects, I have prepared 
a model in accordance with a suggestion of Mr. Francis Galton, 
F.R.S., in which a wheel representing a section of a hollow 
sphere has its axis, upon which it can freely turn, fixed in 4 
frame, which is itself made to revolve in such a manner that the 
