510 
GEOLOGY OF THE FOURTH DISTRICT. 
this part of the rock. It is a very persistent mass, being seen at numerous and distant points. 
Its character as an oolite is as perfect as specimens from Bath, in England ; and its chalky 
and fissile nature, considered alone, would almost induce one to regard it as a more recent 
formation. Its position, however, cannot be mistaken ; for, about one mile below Leavenworth, 
it is seen passing beneath the grey sandstone before mentioned. At this point, without any 
intermixture of the two deposits, we pass from a pure oolitic limestone to an equally well 
characterized quartzose sandstone. 
This limestone was again examined near the mouth of Oil creek, Indiana, where it presents 
the same essential characters as described, and the same order of the parts. Opposite the mouth 
of Little Blue river, on the Kentucky side, the junction of the limestone and conglomerate 
presents a singular siliceous aggregate, containing abundance of shells, and having somewhat 
the character of buhrstone. From this place to the Wabash, there was little of interest to be 
seen ; the rocks approaching the shore in many places, indicated along the whole distance the 
existence of the great Coal formation of the Illinois or Wabash basin. From the section, it 
will be perceived that the Wabash flows in the depression of a synclinal axis, and from thence 
the strata gradually rise to the westward. 
The limestone soon rises from beneath the river level, and continues in view nearly to the 
Mississippi, being obscured only by superficial accumulations. After ascending the Missis¬ 
sippi for some distance, the rock again appears. The great valley, or “ American bottom,” is 
bounded on either side by abrupt cliff’s of this limestone : the river meandering in its course 
from side to side, sometimes runs at the base of the perpendicular rock; while the opposite 
side presents a broad level bottom land, covered for the most part with luxuriant forests of 
primeval growth. These cliffs form some of the most picturesque scenery, and, with the 
small shot towers upon the overhanging margin above, suggest the idea of stupendous castle 
walls of cyclopean architecture, crowned with the sentinel’s towers. 
Between the point of its first appearance on the Mississippi and its final disappearance near 
the mouth of Rock river, I examined it at numerous points, and always found a very uniform 
lithological character, which alone is sufficient to distinguish it from all other rocks, and ena¬ 
ble one to identify it with its commencement in Indiana. The fossils, however, are constant 
and unerring guides, which leave no room for doubt. The rock, on fresh fracture, has a 
peculiar light grey color, much of it crystalline ; while other portions are compact and fine¬ 
grained, presenting the appearances described at Leavenworth. 
At St. Louis I obtained several fossils, principally corals and crinoidea ; all of which, so far 
as I know, differ from those found in any lower rock. Dr. B. B. Brown, of St. Louis, politely 
presented me with specimens of Producta, from his cabinet, which were found in that vicinity, 
and which corresponded with the British P. Martini. Having since had an opportunity of 
examining a small collection of fossils from the carboniferous limestone of England, in the 
Lowell Institute, I found many of the same species as those of this great formation, leaving 
no doubt of the identity of the two. The difficulties, therefore, in the way of comparing our 
rocks with those of Europe, seem in a fair way to be cleared up ; and we learn, that among 
all our limestone formations, in the eastern part of the United States, the true carboniferous 
