CAPvBOXLFEROUS SYSTEM. 253 



at considerable height above the Des Moines river in its 

 valley sides, in Marion. Mahaska, and Wapello counties, 

 as may he seen illustrated in the sheet of sections jnst referred 

 to. Indications of another slight fold have been observed, 

 passing down through Warren, Clarke, and Decatur counties, 

 and sill another is known to have nearly the same course as 

 the East Xishnabotany river, or in other words, that stream 

 occupies a very slight anticlinal ridge throughout the greater 

 part of its course. 



These folds have a general northerly and southerly direction 

 bnt they do not all seem to be entirely parallel with each other. 

 Some of them are so slight that their existence is likely to 

 be overlooked, without a series of extended observations in 

 connection with railroad levelings, particularly those in the 

 western part of the State. It is proper to remark, however, 

 that Prof. St. John and myself arrived at the same conclu- 

 sions in regard to these folds while working separately and 

 without each knowing the other's views. As will be seen by 

 the section from McGregor to the mouth of Broken Kettle 

 creek across the northern part of the State, the strata there 

 also vary very much in the angle of their dip in different 

 parts of the line, as they do in the southern part of the State 

 along the line of the Burlington and Missouri River Eailroad. 

 It will be seen by both these sections, that the strata of the 

 central portions of the State are elevated as a broad fold 

 passing through it from north to south. In the northern part, 

 this fold keeps the Kinderhook beds at the surface, along the 

 line mentioned for a distance of about eighty miles, although 

 the formation is there probably less than one hundred feet in 

 thickness. In the southern part, the same broad fold keeps 

 the Upper coal-measures at the surface on an east and west 

 line for a distance of more than a hnndred miles ; while the 

 strata of Lower Silurian age in northeastern Iowa, and of 

 lower Sub-carboniferous age in southeastern Iowa, dip so 

 rapidly as to be soon lost to view in a westerly direction. 



Westward from the East Xishnabotany river, the strata of 

 the Upper coal-measures seem to have a slight north- 

 westerly dip. 



