300 On the Physical Geology of the United States, §c. 
If such motion has been produced, changes of longitude of 
masses of the earth’s crust must have been effected, such as 
we trace evidences of in the wrinkled, crushed, crumpled, and 
folded strata, which, if laid out or developed in a mathematical 
sense, would occupy much wider areas than they do at the present 
time. 
As the strata were elevated in wrinkles, the upper extremities 
being more remote from the axis of motion-of the earth, the tops 
of the wrinkles would tend by the action of inertia to fall over 
to the westward,* and give a general eastwardly dip to all the 
strata that were highly elevated, such as we see to be almost 
constantly the case along that belt of mountainous country ex- 
tending from Canada to Alabama. 
If a motion to the westward be produced by the tangential 
force due to inertia, both from increased oblateness and from the 
elevation of folds, the effect would be a maximum at the equator, 
and be less and less as the latitudes increased. ‘The effect would 
be to produce a strike to the E. of N. in the northern hemisphere 
and to the E. of S. in the southern hemisphere. Along the 
eartern part of the United States this conformity exists. The 
explanation above offered to account for the disturbed and folded 
strata with an E. 8. E. and 8. E. dip, a N. N. E. strike, and a 
lateral tangential force, seems plausible to the writer. It is based 
on the known laws of nature, it is sufficient to explain the phe- 
nomena in question, and as far as observations have been made 
in the United States it is believed to conform to facts. 
The causes that may be supposed to have produced the eleva- 
tion of islands and continents above the level of the sea, beneath 
which they were once buried; the inclination, contortion, wrink- 
ling, folding and crushing of strata; the elevation of mountain 
chains in former times; the gradual changes of level with refer- 
ence to the sea which have been and still are in progress on parts 
of the earth’s surface, have been briefly considered ; and notwith- 
standing the great variety of causes that have been assigned, 
such as volcanic action, undulatory motion of a fluid interior, the 
expansive force of elastic vapors, tangential forces by collapse 
upon a nucleus contracted by refrigeration, unequal contraction 
of land and water by refrigeration, and the effects of inertia and 
increased centrifugal force as influencing the ocean and the solid 
* The reason for this is illustrated on pages 292, 293, ante. 
