On the Physical Geology of the United States, §c. 295 
which is stated to be gradually sinking ; a large area in the Pa- 
cific which is reported to be gradually sinking. The evidences 
of subsidence are not as easily obtained as those of elevation, 
because we must look for them beneath the level of the sea. 
Still another cause of variation in the relative levels of land 
and sea may be adduced, though it may have had little real in- 
fluence in the production of the effects observed. Any diminu- 
tion in the volume of the earth resulting from secular refrigera- 
tion of the globe, would increase the velocity of rotation on its 
axis, and increase the centrifugal force in a higher ratio than the 
angular velocity. Any such increase would tend to draw off wa- 
ter from the polar regions to increase the oblateness of the sphe- 
roidal form of the earth necessary to give the form of equilibrium 
under these new conditions; and if the crust of the earth be too 
rigid to yield to the same force, land that was before buried be- 
neath the polar seas would emerge above their level ; and dry land 
would be submerged in the equatorial regions. 
If on the other hand the solid materials forming the crust of 
the globe be not too rigid to yield to this force,* the effects of the 
centrifugal force cannot be allowed to have had so great an influ- 
ence in the relative levels of land and water as would be due to the 
other case, in which the crust of the globe was supposed to be 
rigid and unyielding. 
Another point bearing upon the elevation of land may be con- 
sidered in this place. 
coast, the surface was raised forty or fifty feet, so that a stream was made to flow 
in an opposite direction. 
6th. The repeated elevation and depression of the coast of the Mediterranean 
around the Temple of Serapis is considered as an established fact. 
7th. In 1843, there was a sudden elevation of the coast of Sweden. It was 
ealled a sinking of the waters of the Baltic ; but as the adjoining coasts of Nor- 
way, Russia and Denmark, have not changed their water level with regard to the 
coast, and the waters of these coasts communicate freely, the fact cannot be ex- 
plained except by the elevation of the land. During the year 1842, the waters of 
the Baltic were observed to be sinking, and on the 4th of May, 1843, a sudden 
change of level occurred, so that the steamer that was to have left the port of Trave- 
munde on the 18th, was detained until the 2lst. Shoals and rocks never before 
known, made their appearance on the 8. W. coast of Sweden, near the Maelstrom, 
in 1843. (Am. Journal of Science, Vol. xiv, p. 184-185.) 
* It may be inferred that they are not too unyielding to be influenced by this 
force in consequence of the contortions, plications and foldings of the strata that 
have been observed on so many parts of the earth, which have been produced by 
other forces more powerful ; yet this may be supposed sufficient to bend the crust 
of the globe gradually. 
