INDEX TO VOLUME VIII. 691 



PAGE. 



Drift, subdivisions of 7,9 



theories of formation 19 



' ' period, commencement of 2 



Erosion in Illinois 3, 4 



Gas, natural, in Illinois 13,58 



Gas, natural, in Ohio and Pennsylvania 61 



Glacial theory discussed 19 



Helicina occulta in the drift 15 



Lake Michigan, ancient western outlet of 11,14,28 



Lamna, in the drift + 4 



Loess 7.9 



Mammalian remains in the drift 8,23 



Mammoth 8 



Mastodon 8 



Megalonyx 8 



Modified drift 7 



Native copper in the drift 19 



Natural gas and oil in Illinois 58 



Oil, natural, in Illinois 58 



Oxyrhina crassa in the drift t 4 



Ptychodus polygyrus in the drift t 4 



River terraces 7 



RUTLEDGE, W., reports of borings 36,39,55 



SHAW, JAMES, report on northern counties 10 



Terrace epoch 7 



Tertiary age in Illinois 3 



WHITE. Dr. C. A. former extent of cretaceous strata in Iowa 6 



ERRATA IN PART I. 



Page 42, line 3 from bottom, for 100.04 read 100.14, 

 Page 49, line 11 from bottom, for 528-6 read 628-6. 

 Page 62, line 19 from top, for 1,088 read 1,078. 



The Hillsboro boring log, on pages 46 and 47, bearing various evidences of incor- 

 rectness, I wrote to Mr. GEO. C. BBTCE, who kindly furnished me the following cor- 

 rections: 



Ft. In. 



11 Limestone (Shoal Creek) 8 



15 Sandy shale and sandston 63 4 



22 Limestone 6 



25 Clay shale 1 10 



27 Bituminous shale 6 



35 Coal, 1 ft; slate, 6 in.; coal, 1 ft. 6 in. No. 5 3 .. 



Total depth 775 feet. 



(J. L.) 



