Carboniferous of Soiitlnvcstcrn lozva. — Keycs. 347 
Singularly enough, during all of this time little more than the 
bare fact has been recorded. No succession of strata has been 
established ; no subdivisions recognized. Neither has the unity 
of the sequence been demonstrated. All references to the for- 
mation have been in the most general terms. Only local un- 
connected sections have been described. 
The rocks as a whole were conmionly regarded to be far 
less important than they really are. Their maximum thick- 
ness, for example, was placed at 200 feet, whereas in reality the 
ineasurement is over five times as much. 
Although from investigations prosecuted in the neighbor- 
ing states of Missouri, Nebraska and Kansas it has been, of 
recent years, inferred that the thickness of the "upper coal 
measures" was much greater than the estimate given by 
White,* his account has long remained the only accessible 
information on that part of the state of Iowa. Much imcer- 
tainty has thus always existed concerning the geology of the 
region. This is well shown by Call's planst of certain deep 
wells that were put down at Red Oak and Glenwood. The lat- 
ter, for instance, which begins in the Plattsmouth limestone, 
is stated to pass through only 150 feet of strata belonging to 
the "upper coal measures." In this formation the well ac- 
tually penetrates nearly four times the distance mentioned. 
Similar statements regarding other deep drill holes were 
wholly conjecture. 
As the region came to be investigated many new facts 
began to furnish substantial data regarding the real extent and 
character of the formation. The prevailing notions were 
changed very materially. From observations made along the 
Missouri river Toddt was led to state that a very noticeable 
flexure existed south of the Platte river in Nebraska ; and that 
a thickness of the "upper coal measures of at least 350 feet was 
demanded by the facts." 
After the present geological survey of Iowa was organized 
much local information was obtained regarding the southwest- 
ern part of the state. For several years, however, pressing 
duties elsewhere prevented the general geology of the "upper 
^Geology Iowa, vol. I, p. 298, 1870. 
tProc. Iowa Acad. Sci., vol. I. pt. ii. p. 60, 1892. 
|Proc. Iowa Acad. Sci., vol. I, p. 58, 1890. 
