244 Notes oni. American Geology. 
Oswego county and forms the banks of Salmon river. Nota 
ry species of shells or plants is common to’both. The former 
is highly inclined, and on its edges rests unconformably the ¢eal- 
eiferous sandrock of Baton, then follows the sparry limerock of 
~ the same author, with some fossils peculiar to it ; above that the 
limestones and shales of the Trenton series, several hundred feet 
thick, and then the Salmon river sandstone follows in the as- 
cending order. This shows the great danger of error in endeav- 
oring to identify strata over large areas, if we neglect to appeal 
to the evidence afforded by paleontology, and rely too exclu- 
sively upon the ever varying mineral composition of rocks, which 
it is obvious may present similar features in Geape: of widely 
different age. 
The present grand undulations or ‘aclined planes of the sur- 
face of the United States, considered in reference to their broader 
outlines, are owing to the position which the transition have been 
compelled to assume, by the unequal rise of primary chains. This 
has arisen from its vast aggregate thickness and enormous unin- 
terrupted extent. Beginning, as it does, on the border of the. 
"Arctic sea, it extends, in some parts of its range, unbroken by 
"granite peaks, quite to the center of Alabama, while it extends 
east and west, from the Appalachian chain to Engineer canton- 
ment on the Miskouni river. It, therefore, on a rough estimate, 
will be two thousand four hundred miles north and south = one 
thousand four hundred in extent east.and west. 
_ The upheaving force, acting over so vast an area, has only 
‘next the mountain chains greatly disturbed and inclined the strata, 
rere the mass nearly horizontal to the eye, but rising and fall- 
ing in enormously extended, slightly inclined planes and undula- 
tions. It is to the re-entering angles or syuclinat lines of the 
planes that we owe the course of many of our large rivers. East 
of Little Falls on the Mohawk, that river rans many miles in @ 
depression caused by the gentle dip of the strata on the nort 
bank, and their gentle rise on the south. The St. Lawrence 
flows in a profound synclinal line, as may be seen by reference 
to Mr. Emmons’ section in the New York geological reports for 
this year. Dr. Hildreth informs us, that the formations in Ohio 
dip towards the center of the valley of the Ohio river, and as 
they reappear at higher levels in Kentucky, there can be no doubt 
_ a synclinal line has determined the original course of. that river. 
