CARBONIFEROUS LIMESTONES OF LOWA. 99 
direct line, nearly two hundred miles, in a northwesterly direction, up the valley 
of the Des Moines.* 
It is bounded by an irregularly undulating line, as follows: commencing where 
the line between Iowa and Missouri crosses the Des Moines River, near the west 
border of Lee County; thence, nearly north, to the northeast corner of Washington 
County; thence, with a northwesterly curve, to the Iowa River, which it crosses 
in Township 81 north, Range 8 west, of the 5th Principal Meridian, not far from the 
lme between Johnson and Iowa Counties; thence, up the valley of the Iowa, some 
twenty-five miles, when it recrosses that river, near the southeast corner of Tama 
County; thence, curving through Tama County, and again crossing the Iowa, to 
near the centre of the east line of Marshall County; thence, along the water-shed 
of the Iowa and Cedar, recrossing the former near the northeast corner of Township 
87 north, Range 30 west, of the 5th Principal Meridian; thence, with a westerly 
curve, up the Iowa, and continuing west of that river to the “ Big Woods,” where it 
recrosses, for a few miles, returning to the west side of that stream, and running in 
a nearly due west course to the Des Moines, which it crosses six miles above the 
Lizard Fork; thence, with a southwesterly curve, towards the head-waters of the 
Three Savane; thence, down the valley of Neshnabotna, to the State line. 
It is to be remarked, that this boundary line was, in some places, of difficult 
determination ; and, especially in the north and west, obscure and ill-defined for 
considerable distances ; chiefly on account of the depth and extent of the superficial 
sedimentary deposits. 
Along the course of the Mississippi, the belt of Carboniferous Limestone cannot 
be traced north much beyond its confluence with the Iowa. Here it is lost beneath 
sandstones of the coal-measures, which appear in the Muscatine bluffs, and are 
remarkable, as well for the fine specimens of Lepidodendrons and Ferns which they 
afford (see Table VL, Figs. 1, 2, 3, 4, 5, 6, and 7), as for the globular form and 
great size of the curious segregations of argillaceous sandstone, which are shown in 
the subjoined wood-cut, as they have been laid bare in one of the quarries, half a 
mile below the town of Muscatine. , 
About five miles below the mouth of Pine Creek, these carboniferous sandstones 
are succeeded by limestones belonging to the Devonian period ; they reappear, how- 
* After crossing the Iowa boundary line into Missouri, the boundary line of this coal-field bears nearly 
south, through Clark, Lewis, and Marion Counties, to near the junction of the Three Forks of Salt River. 
Thence through the western part of Ralls County, towards the head waters of Riviére au Cuivre, in the 
eastern part of Audrain County, and northwestern corner of Montgomery County. Thence it sweeps, in 
a southwesterly curve, through Oalloway County, towards the Missouri River, which it crosses near its 
confluence with the Osage; leaving a belt of country, some ninety miles wide, between this coal region 
and the outcrops at Charbonniére, and the coal-pits worked on Riviére des Péres, in St. Louis County. 
These are, in fact, outliers of the Illinois coal-field. From the Missouri River the boundary bears, with 
a westerly curve, up the valley of the Osage, north of that river, which it crosses, but for a very limited 
distance only, at three points: in Camden County, near the mouth of the Niangua; in St. Clair County, 
near the mouth of Sac River; and in Bates County, near the confluence with the main river of the Little 
Osage. Thence the line bears, with a northerly curve, towards the western confines of Fayette, recrossing 
the Missouri at Wellington ; thence up the valley of that river, keeping from ten to twenty-five miles 
from the river, to the State line. 
