INTRODUCTION. 
53 
Section of strata in New-York and Pennsylvania. Section of strata in the Mississippi valley. 
Coal measures, 
RED 6HALES, 
Conglomerate, 
Catskill-mountain group, 
Chemung and Portage groups, 
Hamilton group. 
Coal measures, 
Kaskaskia limestone, 
Ferruginous sandstone, 
St. Louis limestone, 
Warsaw limestone, 
Keoicuk limestone, 
Burlington limestone, 
Chemung and Portage groups, 
Hamilton group. 
That interval of time, which in the east is marked by the accumu¬ 
lation of the Catskill-mountain group (Formations ix and x of the 
Pennsylvania Survey), and the Red-shale group (Formation xi), is 
marked in the west by the great Carboniferous limestone series of the 
Mississippi valley. These formations are widely different in lithological 
characters, and nowhere commingling, unless it he in the eastern part 
of Tennessee or in Alabama ; and at this time it has not been shown 
which of these has the precedence. A careful examination of the section 
on the Mississippi shows such a close sequence between the higher 
beds of the Chemung group and the lower beds of the Burlington 
limestone, that we find it difficult to believe that any interval or cessa¬ 
tion of deposits has occurred. On the other hand, some beds of coarse 
material mark the junction of the Chemung group with the base of 
the Catskill-mountain formation in Eastern New-York; and though 
the entire fauna of the Chemung group suddenly ceases, there is no 
evidence of a long interval between the termination of the one and 
the commencement of the other. 
Admitting this view, we have to contemplate a wide extent of coun¬ 
try, lying between New-York and the most easterly extension of the 
Carboniferous limestones, as an area over which no sediments were 
deposited, nor calcareous formations accumulated, during this period. 
It may not be uninteresting in this place to present a few facts 
relative to this great Carboniferous limestone formation of the Missis¬ 
sippi valley; since, hereafter, in the consideration of the sequence of 
