296 On the Physical Geology of the United States, Sc. 
It has been shown that the centrifugal forces vary inversely 
as the cubes of the radii. It is also well known that bodies of 
different densities are affected by the centrifugal force in proportion 
to their densities. As the solid materials of the globe are more 
dense than water, they would be more influenced by variations in 
the centrifugal force in proportion to their specific gravities ; and 
as the centrifugal force is greatest under the equator, any diffused 
subterranean forces that may exist, and that tend to elevate por- 
tions of the earth’s surface by their elastic tension, would be most 
effective under the equator, where gravity is less, and the cen- 
trifugal force greater than on any other portion of the earth’s 
surface. 
May not this cause have had some influence in producing the 
heights of mountains under the equator? It is well known that 
the highest are within or near the tropics, and that most of the 
highest in Africa and South America are almost under the equator. 
Again, the influence of an increased velocity of rotation of the 
earth, would tend to make the polar regions flatten, and the equa- 
torial regions become still more protuberant. Lines of fracture 
might be expected in the direction of small circles parallel to the 
equator, at a distance intermediate between the poles and the 
equator, where the curvature resulting from such a ince of esa 
would be the greatest.* 
Ranges of mountains mostly of primary rocks, do, in fact, al 
most encircle the globe between 40° and 50° of north latitude, 
and in North America the strike is, in many parts, nearly E. and W. 
The great fractures seem to have been made nearly in this di- 
rection, even where the strike is different. The highest peaks 
of the Rocky Mountains, so far as is known, are in about 40° of 
north latitude; those of northeast New York and the White 
Mountains of New Hampshire about 44°; the ranges of the 
Pyrenees, the Alps, the Apennines, and the Carpathian Moun- 
tains in Europe are between 40° and 5 50°; the Caucasus Moun- 
tains, the Taurus Mountains, the iindes Koo Mountains, and 
the Thian Chan Mountains in Asia, are among the most elevated 
on the globe and are found between 35° and 45° north latitude, 
and have a trend nearly E. and W. 
* Other fractures in the directions of meridians might be expected if the oth 
increased in its equatorial diameter. 
