ROCK FORMATIONS OF THE WESTERN STATES. 
507 
west or southwest; and at Madison, the base of the cliff limestone has approached within 
one hundred and fifty or two hundred feet of the river. From this point it continues to dip 
in the same direction, gradually approaching to the river level, and finally disappearing be¬ 
neath it at Louisville, or the Falls of the Ohio. The river, at the time, being high, did not 
permit an examination of the rock directly at the falls ; but the excavation of the canal below 
Louisville has developed, in the loose fragments, the character of the rock, which consists, 
apparently, of the water lime, and perhaps some portion of the Onondaga salt group, with 
the lirqestones above. The most satisfactory exhibition, however, was a few miles further 
up the river, where the rocks are very well exposed. Along the line of railroad, and in 
the banks of a small stream, about three miles from Louisville, the same rocks are seen. The 
highest mass at this place, contains a species of Calymene * * characteristic of the corniferous 
limestone of New-York, as well as several shells equally so ; among these, a peculiar variety 
of the so called Atrypa prisca, and a species of Strophomena; both shells are confined to 
this mass. Below this was seen a rock with Favosites and Cyathophylli , which could be 
identified with no other rock than the Onondaga limestone, possessing all its essential features, 
both as regards lithological and palaeontological characters. Passing from this over strata re¬ 
sembling the lighter colored portions of the water-lime series of New-York, we came upon a 
drab-colored mass, in thin layers, abounding in Catenipora and Favosites; and below this a 
lighter or ash-colored limestone, in thick courses, destitute of fossils. Such, simply, was 
the order in which the rocks were examined at this place, and from which collections were 
made. 
From the examinations made here, at Madison and other points, the unavoidable conclu¬ 
sion is, that in the cliff limestone we have the Helderberg series of New-York; or at least 
the two persistent members, Onondaga and Corniferous, with the Water-lime, and, perhaps, a 
meagre representation of the Salt group, together with the Niagara limestone. It seems con¬ 
clusive, therefore, that the Cliff formation, as defined in Ohio, embraces all the existing for¬ 
mations from the Corniferous limestone to the Clinton group inclusive, that formation having 
been detected in this State, and one of its most important fossils in New-York (Pentamerus 
oblongus ) is abundant in Indiana and Iowa. 
After making these investigations in the vicinity of Louisville, I had the gratification of 
seeing, in the cabinet of Dr. Clapp, at New-Albany, many of the fossils common to the rocks 
of New-York, and which fully confirmed my views relative to the position of those examined. 
These fossils were principally from the rock at the falls of the Ohio. From comparing my 
observations of other rocks with those made by Dr. C., I became still further convinced of 
the identity of different portions of the formations of the West with those of New-York,t and 
that the limits of many of the rocks were as well marked there as at the East. 
* Calymene crassimarginata of this Report, page 172. 
* From a letter of Dr. Clapp to the Philadelphia Academy of Natural Sciences, dated February, 1942, I am happy to see that 
his views regarding the identity of the rocks of that region with certain formations of New-York, essentially correspond with 
■what I had expressed in the American Journal of Science of January preceding. 
64* 
