STRATIGRAPHIC GEOLOGY 347 



remote from the real one. The recent report on Monroe county, 

 the southeastern one of Michigan, by the Geolooical Survey of that 

 state, has added greatly to our exact knowledge of this formation. 

 The writer has also collected considerable data in this state, 

 Michigan, Ontario, and New York for a bulletin upon this for- 

 mation. The "'Corniferous limestone" is composed of the two 

 distinct formations of the Columbus and Delaware limestones 

 which have never been separately mapped. It may be mentioned 

 in passing that Dr. Charles K. Swartz of Johns Hopkins University 

 has in preparation a valuable monograph describing the strati- 

 graphy and paleontology of these formations and the writer and 

 his students have done something in this same line. The next 

 large division, the "Waverly Group," in central Ohio, is composed 

 of six clearly defined formations, viz. : the Bedford shale, Berea 

 sandstone, Sunbuiy shale, Cuyahoga, Black Hand and Logan for- 

 mations, no one of which has ever been mapped separately. It is 

 also probable that there will be some change in the units of this 

 series in the northern part of the state and perhaps in the southern 

 as compared with those of central Ohio. The writer and his 

 students have given considerable attention to the problem of the 

 classification and description of the Waverly series. Finally, the 

 area colored as the "Coal Measures" includes the upper portion of 

 the Pottsville, the Allegheny, Connemaugh and Monongahela for- 

 mations together with the Dunkard formation, the latter probably 

 of Permian age. Although these formations are not mapped 

 separately, still something has been done toward furnishing the 

 data for such representation in tracing the various coal seams 

 of the state. Certain ones, as for example the Upper Freeport, 

 Pittsburg and Waynesburg coals indicate formation limits and the 

 recent work of Dr. Bownocker" and his assistant in tracing the 

 Pittsburg coal will be of value in separating the Conemaugh and 

 Monongahela formations. There also remain the subjects of 

 glacial "and physiographic geology which have become of great im- 

 portance and interest in these later years. Concerning glacial 

 geology much has been accomplished by the United States Geo- 

 logical Survey in this state as is shown in Leverett's Monograph 

 entitled "Glacial formations and drainage features of the Brie 

 and Ohio basins." 



It is not the writer's intention to criticise in any way the work 

 of the earlier members of the Ohio Geological Survey, and if any 

 have formed that opinion they have missed entirely the aim of this 

 paper. Indeed, on the contrary, he often wonders at the large 

 amount of correct and valuable information which they brought 

 together, hampered as they were financially, pressed for time, and 

 often laboring under most discouraging conditions. The fidelity, 

 perseverence and faithfulness of those men merit all honor. 



Neither has the writer any criticism to make of the present 



