BROADHEAD — HIST. MEMOIR OF MISSOURI GEOL. SURV. 633 



The First Geological Survey of Missouri approximately indi- 

 cated the area of our coal fields, defining the boundary thereof, 

 and showed that there were three principal divisions, viz., the 

 Upper, the Middle, and the Lower coal measures. It located 

 many important coal mines, and stated where our principal 

 known lead mines were. Dr. Litton's careful survey of the 

 lead mines of South-east Missouri informed us of the mode of 

 -occurrence and manner of working the mines, and gave analyses 

 of the lead. 



Prof. Swallow correlated remote sections and classified the 

 rock groups, so that the scientific world might know what for- 

 mations existed in the State. His vertical section has not been 

 materially changed since then. Some provisional names of 

 groups have given place to others deemed more appropriate. 



In the three series of the coal measures the geological surveys 

 have shown that the Upper was mostly barren of coal, the Lower 

 productive. 



Broadhead's map of the coal fields, in Atlas of 1S72, defines 

 the line between the barren and productive coal measures. This 

 was not previously known, and a glance at the map will at once 

 indicate where coal might be profitably mined. 



There are beds of black slate occurring at intervals in the coal 

 measures, but there are other similar strata which are found in 

 older formations which the Missouri survey demonstrated con- 

 tained no coal. Careful studies of the Missouri coal measures 

 also showed that its beds could be readily recognized by the or- 

 ganic remains peculiar to this group of rocks, until then but little 

 known to the palaeontologist. 



Dr. Schmidt's iron ore map, in the Report for 1S72, indicated 

 by signs the proportional amount of iron in certain districts — 

 very important to the prospector. 



The Geological Report for 1874 pai'ticularly described certain 

 coal districts, giving the depth, area, and approximate yield of 

 coal which might be expected under certain areas. These coun- 

 ties have since shown a marked increase in population and coal 

 mining operations. The Report of Bates Co. (by G. C. Broad- 

 head) was reprinted in a "History and Gazetteer" of the county, 

 and many extracts from it published in a circular which was 

 published and widely circulated. The attention of railroad com- 



