CONTENTS. 



VII 



PAET SECOND. 



GENERAL GEOLOGY. 



CHAPTER I.— AZOIC, LOWER SILURIAN, UPPER SILURIAN, AND 

 DEVONIAN SYSTEM. By C. A. White. 



1. Azoic System Page 167 



2. Lower Silurian System 171 



3. Upper Silurian System 182 



4. Devonian System 184 



CHAPTER II.— CARBONIFEROUS SYSTEM, SUB-CARBONIFEROUS 

 GROUP. By C. A. White. 



1. Kinclerhook Beds Page 191 



2. Burlin 4km Limestone 201 



3. Keokuk Limestone 210 



4. St. Louis Limestone 215 



5. Concluding Remarks upon the Sub-carboniferous 



Group 222 



6. Unconformability of the Coal-measures upon the 



older rocks, and of the St. Louis Limestone upon 

 the older formations of the Sub-carboniferous 

 Group 225 



CHAPTER III. — CARBONIFEROUS SYSTEM (Continued), COAL- 

 MEASURE GROUP. By C. A. White. 



1. Lower Coal-measures Page 232 



2. Middle Coal-measures 241 



3. Upper Coal-measures . - 241 



4. General Observations upon the Carboniferous 



Rocks of Iowa 250 



5. Practical Conclusions 258 



CHAPTER IV.— CARBONIFEROUS SYSTEM (Concluded), MIDDLE 

 COAL-MEASURES. By O. H. St. John. 



1. General Surface Features Page 264 



2. Geological Structure 267 



3. General Section of the Middle Coal-measures 272 



4. Economic Geology 283 



