68 
PALEONTOLOGY OF NEW-YORK. 
with small exceptions, the entire country from the Atlantio slopes to 
the base of the Rocky mountains; that the same geological formations 
occupy the mountain chain and the plateau. But while the horizontal 
strata give their whole elevation to the highest parts of the plain, we 
find the same beds folded and contorted in the mountain region, and 
giving to the mountain elevation not one-sixth of their actual measure¬ 
ment. 
We are accustomed to believe that mountains are produced by uphea¬ 
val, folding and plication of the strata ; and that from some unexplained 
cause, these lines of elevation extend along certain directions, gradu¬ 
ally dying out on either side, and subsiding at one or each extremity. 
In these pages, I believe I have shown conclusively that the line of 
accumulation of sediments has been along the direction of the Appa¬ 
lachian chain; and, with slight variations at different epochs, the course 
of the current has been essentially the same throughout. The line of 
our mountain chain, and of the ancient oceanic current which deposited 
these sediments, is therefore coincident and parallel; or, the line of the 
greatest accumulation is the line of the mountain chain. In other words, 
the great Appalachian barrier is due to original deposition of materials, 
and not to any subsequent action or influence breaking up and dislo¬ 
cating the strata of which it is composed. 
To be satisfied of this, it seems only necessary to compare the eastern 
and western exposures of the formations ; for here the valleys, cutting 
through the rocks of the several groups down to the lower limestones, 
or to the Potsdam sandstone, present mountain ranges of several thou¬ 
sand feet on either side ; while in the valley of the Mississippi, where 
the strata have thinned, the same denuding action has produced low cliffs 
or sloping banks of one or two hundred feet in height. Therefore had 
the country been evenly elevated without metamorphism or folding of 
the strata, making the lowest palaeozoic rocks the base line, in the 
States bordering the Atlantic we should have had higher mountains 
and deeper valleys, wherever the series was complete. At the same time, 
the great plateau on either side of the Mississippi river would have 
