STRATIGRAPHICAL GEOLOGY 
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under Norwood, prior to 1858, and how much subsequently under 
Worthen, is now impossible to say. The earlier results are doubt¬ 
less more extensive than is indicated by the scant notes incor¬ 
porated in after years by Worthen in his County reports. It is 
quite likely that not only Englemann and Norwood, but Owen, 
Lyon, Pratten and perhaps others had early begun to suspect that 
the great Concretionary limestone, which we now call the St. Louis 
limestone, was not actually the summital member of the Subcar- 
boniferous (Early Carbonic) section as was at that time so gen¬ 
erally believed. Doctor Norwood, then State Geologist, must have 
had in mind this very suspicion when, in the spring of 1853, he 
especially details his assistant, Worthen, to go down to the south¬ 
ern part of the state and determined, if possible, the relative posi¬ 
tion of the St. Louis limestone and the beds forming the bluffs 
at Chester, which we now designate the Kaskaskia limestones. The 
attendant circumstances Worthen relates at length when claiming 
priority for his manuscript title Chester over Hall’s name defined 
and published a decade before. 
It may be well doubted whether in the beginning Worthen ac¬ 
tually saw conditions between Prairie du Rocher and Chester so 
clearly as he thought he did a dozen years later, when the supposed 
facts had been fully demonstrated to obtain. It may be also ques¬ 
tioned whether Norwood was so doubtful of the correlations of 
Worthen’s observations as the latter would have us infer. One 
would rather surmise that Worthen’s findings really confirmed 
Norwood’s suspicions and that so much to his liking had they 
proved that the director at once set off to see with his own eyes 
what his subordinate had reported. 
When, then, Worthen left the Illinois Survey, soon afterwards, 
and went with Hall to Iowa he is not slow in communicating to 
the latter his recent discoveries at Chester. It so happens that 
this constituted the missing link to Hall’s classification of the Sub- 
carboniferous rocks of the Mississippi Valley — a fact which Wor¬ 
then could not perhaps fully realize at that time. Hall soon, in 
1855, has his assistant go with him over the ground above Chester. 
With his usual promptness to forestall priority in others in all mat¬ 
ters relating to the American Paleozoics, for he had not yet given 
up his defense of his long cherished New York system, he incor- 
