330 TRANS. ST. LOUIS ACAD. SCIENCE. 



of the groups correlate readily among themselves ; while of the 

 third group one section was personally examined only in part, 

 another is isolated, and the last is necessarily less satisfactory 

 than an outcrop section, and the group thus becomes of secondary 

 importance. 



The hiatus between the first and second groups, measured be- 

 tween the 5-foot coal seam and the seam so conspicuous on Salt 

 river, was estimated to be 45 ft. at the Pavson and Bevier bridge 

 sections, 50 feet at the Excello road and Excello Bridge sec- 

 tions, 50 feet at the exposures northwest of Macon (also referred 

 to Bevier bridge), 40 feet at the Mayfield and Excello bridge 

 sections, and 60 feet between the Excello bridge section and the 

 exposure on the road toward McGee College. It is believed that 

 all of these estimates are within 20 or 35 per cent, of the truth. 

 The mean is about 50 feet. This hiatus is in part filled by the 

 Broadhead section, a portion of which was verified and the 22- 

 inch coal seam noted near its centre correlated with the iS-inch 

 seam of Patton creek. On adding the upper part of this sec- 

 tion to the Excello bridge sequence, and juxtaposing with that of 

 Claybank creek, the hiatus appears to be nearly filled ; but, since 

 none of the strata can be certainly correlated, there is some un- 

 certainty as to the relation ; and the exact thickness of the miss- 

 ing strata cannot be ascertained. 



On juxtaposing the Broadhead section and the Macon boring, 

 the relations of the strata penetrated liy the prospect drill become 

 at once apparent. It is true that the limestone above the lowest 

 coal becomes ''calcareous shale" in the boring record, that the 

 vertical interval between the coal seams in the exposure appears 

 too small unless the larger estimate of the "slope" (number 4 of 

 the section) be adopted, and that there are a few other incongru- 

 ities ; but, when the uncertainty inseparable from the methods of 

 determining the stratigraphy in the one case and the thickness in 

 the other is considered, this discrepance becomes insignificant. 

 The Lower Brick-yard section also falls into a position consistent 

 at once with the stratigraphy and with relative altitudes ; but 

 the imperfection of the section is such that the coincidence can 

 scarcely be regarded as corroborative of the accuracy of the 

 correlation. 



Accordingly the several exposures may safely be combined as 



