ROCK FORMATIONS OF THE WESTERN STATES. 
509 
Pursuing my investigations down the Ohio from this place, I found that the grey sandstones 
with intercalated limestone were succeeded by a thick and persistent mass of limestone, pre¬ 
senting features unlike any of the limestones seen in New-York or Ohio. By reference to the 
section, this limestone will be seen extending eastward to the vicinity of New-Albany, Indiana, 
and passing beneath the level of the river, near Leavenworth, about fifty miles below. It is 
visible, forming a cliff along the river, for nearly the whole of this distance, where it passes 
under the conglomerate, or its representative, a coarse grey sandstone, showing diagonal lines 
of deposition, with seams and nodules of hydrate of iron. This limestone reappears upon 
the river in several places between Leavenworth and the Wabash, at some of which exami¬ 
nations were made. Beyond the Wabash it reappears and continues to the Mississippi river, 
forming a low cliff often for many miles in succession. On the Mississippi, above the junc¬ 
tion of the Ohio, it soon appears, forming at first but slight elevations, but soon rising into 
cliffs of from one hundred to two hundred feet in height. It presents this character of cliffs 
nearly to St. Louis, beyond which place it does not rise so high, but continues in view as far 
as the Rock river, and extends up this stream beyond Dixon’s ferry. From this rapid sketch 
it will be seen, on reference to the map, that this limestone occupies an extensive area east of 
the Mississippi river, and stretching westward its limits were unknown. On the south of the 
Ohio it is known to extend into Tennessee, and from the Reports of Prof. Rogers, it is a very 
extensive and important rock in Virginia. It thus becomes equally important with any of the 
great limestone formations heretofore described in this country, in regard to position and 
extent. When it shall become more generally known, it will be found a prominent horizon 
for the proximity of the coal strata, as, in its absence, is the conglomerate further east. 
The examination of this limestone at Leavenworth, gave the following characters : The lower 
part of the rock is compact and fine-grained, breaking with a smooth conchoidal fracture. 
This portion has been used for lithographic stones, and for small pieces serves the purpose 
very well. Above this portion the character is somewhat irregular, with light-colored chert 
or hornstone, which is often translucent. I was unable to find any fossils thus far upward, in 
the mass at this place. Above the cherty layers the rock becomes coarser grained or semi, 
crystalline, and contains numerous fossils of the genera Delthyris, Atrypa, and large numbers 
of the Pentremites. The most remarkable fossil of this portion of the rock, and which occurs 
just above the fossils named, is the Archimedes of Lesueur, a singular coral, appearing as 
an expansion somewhat like the Retepora* twisted spirally round an axis ; or rather, the edge 
of the coral, by thickening and folding, forms the axis. This curious fossil always holds the 
same position in the rock, the character of which differs from that above or below, being often 
ferruginous or yellowish in color and fine-grained. This portion of the rock contains, besides 
the Archimedes, one or two other corals, and one or more species of Crinoidea. 
This is again succeeded by a beautiful light-colored oolitic mass, containing numerous 
fragments of fossils, the principal of which are Producta, some perfect specimens being 
obtained. A Trilobite, a portion of the head of which resembles an Asaphus, also occurs in 
I am informed by Mr. Lyell, that Mr. Lonsdale regards this fossil as a species of his genus Tenestella. 
