252 GENERAL GEOLOGY. 



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tlie Upper coal-measure formation with probably only the 

 drift intervening. Allowing for the deep deposit of drift 

 which evidently exists at Highland and in its vicinity, we 

 may assume that the strata of the Upper coal-measures 

 there reach an altitude of something more than six hundred 

 feet above low water at Burlington. Now the estimated and 

 measured thickness of all the formations which successively 

 occupy the surface between Burlington and Highland is 

 not much above one thousand feet; consequently, if the dip 

 of those strata were uniform and direct to the westward, the 

 Burlington limestone would appear in the valley of Skunk 

 river at Chicaqua, and the Keokuk limestone in the valley 

 of the Des Moines at Ottumwa, whereas the St. Louis lime- 

 stone alone is found at both those places. This, as well 

 as other observations, plainly shows that the westerly dip 

 of the formations is not direct and uniform. 



Although the Kinderhook beds and Burlington limestone 

 have an exposed thickness in Des Moines county of nearly 

 two hundred and fifty feet, the westerly dip is so great in 

 that part of the State that these formations are seen no more 

 west of the western boundary of that county. Continuing 

 westward we find the St. Louis limestone alone exposed in 

 the valleys which we cross, for a distance of more than sixty 

 miles, showing that within that distance the strata have 

 lost all, or nearly all, their westerly dip. We have still 

 further evidence that a slight easterly dip of the same 

 formations occurs westward from the Des Moines river on the 

 line of the Burlington and Missouri river railroad, besides 

 minor folds or undulations at intervals between Burlington 

 and Highland. These are partially shown in the sheet of 

 sections across the State, which accompanies this report. 



These folds are slight, it is true, but they are, nevertheless, 

 real. One of them has been before noticed as having brought 

 up the Keokuk limestone at Bentonsport, on the Des Moines 

 river where it has carried up with and above it, the St. Louis 

 limestone and Lower coal-measure strata. Another broad 

 one has brought up the St. Louis limestone, so that it appears 



