J, Hall on Carboniferous Limestones of Mississippi Valley, 201 
that point and Cap au Gris we again notice only broad undula- 
tions, which reveal successively all the strata from the Carbonif. 
erous limestone to the lower Silurian rocks. In approaching 
pau Gris from the north, there is a gradual rising of the 
lower strata, so that the Trenton limestone is beautifully defined 
for a considerable distance; and beneath it lies a magnesian 
estone, apparently of no great thickness. The dip to the 
northeast increases, and from beneath these limestones, the sand, 
stone rises in a bold escarpment continuing for three-fourths of a 
e, and presenting several hundred feet of thickness. This 
elevation suddenly declines to the southward, and we find the 
Burlington or lower Carboniferous limestone standing vertically 
by the side of the lower sandstone. The limestone soon assumes 
asteep and gradually a more gentle dip to the south, and the 
succeeding members come in successively. This fault, which is 
in fact an anticlinal axis, has a northwest and southeast direction, 
and, according to the observations of Mr, Worthen, extends far 
Into Ilinois, 
_ Below St. Louis, in the vicinity of Selma, there is another de- 
cided anticlinal axis, bringing up the lower sandstone. Accord- 
ing to the Missouri Report the lower limestones and sandstones 
are again brought up in the vicinity of Bailey’s Landing; but I 
have personally examined the strata at this place only so far as 
to decide that the Upper Silurian strata appegrsrors naneasto 
Upper Helderberg and Hamilton groups, beyond which the Car- 
boniferous limestones appear to come on unconformably in 
Still another axis of very decided character brings up the 
Trenton limestone in great ies at Cape Girardeau on the Mis- 
souri side, and at Orchard Creek below Thebes on the Illinois 
a line drawn from Fountain Bluff on the Mississippi to near 
j its axis 
t these low axes crossing the Mississippi are the results of 
the great movement which elevated the fundamental strata of the 
Western mountain chain, we can have little doubt. The forces 
that there acted upon the huge pile of sedimentary strata, raising 
