358 Transactions. —Geology. 
150,000 years, would be 10,000 miles of such hills, which is much more 
than denudation would be able to wash down to the sea level in the same 
time. 
As soon as the expansion had taken place a great part of it would be 
lost at once, for the heat was only just sufficient to cause the expansion, 
and having done its work it ceases to exist. 
Molecular attracton and gravity would at once begin to pull down the 
elevation again, heat would be again generated, and would prevent further 
compression until the heat was lost by radiation. The first movement of 
depression would be almost instantaneous, indeed, the hill would not, 
unless the material were perfectly elastic, reach the full height above given; 
it would rise, however, to a height greater than that it could maintain, the 
excess of elevation being a function of the elasticity of the stone; it would 
then sink, rapidly at first, and afterwards very slowly. 
The normal condition of the earth is thus one of subsidence, and if it 
were not for volcanic action the solid land would soon sink beneath the sea 
level. 
Let the figure represent a section through the 
poles of the earth, the dark line being the form before 
FIG.2 and the fine line that after fracture. The equatorial 
belt having fallen in on to its supports, as above 
described, it would seem at first sight that there 
would be no compression in the polar sections, as the 
line E p Eis shorter than E P E, and extension 
rather than compression would be looked for. When, 
however, the crust yielded to the tensile strain, the 
point p would be transferred bodily to P, and the 
curve E p E having a longer radius of curvature than E P H, there would 
be, in proportion to the area, quite as much compression before it could fit 
to its new place as there was in the equatorial belt. 
We have hitherto regarded the sun and moon as being in the plane of 
the equator. Their declination would not have much influence on the 
amount of the strains to which the crust is subjected, but it would largely 
alter their direction, the pole of the tidal ellipsoid would travel nearly 30 
degrees from the pole of the earth, instead of being coincident with it. This 
would greatly lessen the tendency of voleanic fractures to run in the 
cardinal points of the compass. 
When the earth changes its form the parallels of latitude passing through 
E E do not change their diameter, and there should be less volcanic action 
due to north and south lines of fracture at least, at these parallels, than else- 
where, the sun and moon’s declination, however, by making these points 
m 
EQUATOR 
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m 
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