68 PROCEEDINGS OF THE PHILADELPHIA MEETING 



hill country, <'iii«l in this narrowing do not show a close relation to rock hard- 

 ness. 



5. About the margin of the Ozarks a peneplain, probably of Tertiary age, 

 has apparently been tilted rather sharply, so that it now slopes strongly toward 

 the lowland to the northeast, and this slope is to a considerable degree inde- 

 pendent of rock structui-e and drainage lines. 



6. The surface features, the structure, and the buried peneplains of the 

 upper end of the Mississippi embay ment seem to show uplift since the Ter- 

 tiary strata were laid down. 



7. The position of the Mississippi River shows lack of adjustment, for it 

 flows on the side of a trough, both structural and physiographic. The natural 

 place for the river between St. Louis and Cairo is in the low, soft rock country 

 50 miles or more east of its present position, and the evidence is now practi- 

 cally conclusive that it was not forced out of such a course by a glacier, and 

 also that it is not a superposed stream. 



8. The drainage on the east side of the Mississippi is undergoing readjust- 

 ment, the principal process being the development of many new small tribu- 

 taries which are driving divides eastward. 



9. Certain facts suggest that the valley of the Mississippi has in large part 

 been carved in Pleistocene time, and apparently its youth and the topographic 

 unconformity between it and the bordering surface forms, though due in pari 

 to enlargement of basin and perhaps glacial floods, can not be fully accounted 

 for except through deformation. 



10. The foi'm of the valleys of the Ozarks is believed by the writer to be 

 such as to indicate that for the most part they ha^e been carved since late 

 Tertiary time, and the lower parts of them in particular show evidence of 

 comparatively recent uplift. 



Some facts suggest that the deformation consisted in part of downwarp of 

 the southern Illinois and western Kentucky lowlands; but however that may 

 be. the downstream rise of terraces and buried valley bottoms seems susceptible 

 of no interpretation other than relative uplift, and this, together with the fact 

 that the other lines of evidence are accordant, are believed to put on a firm 

 basis the conclusion that this region has suffered deformation in late Tertiary 

 and Quaternary time. 



Presented by title in the absence of the author. 



OLD SHORELINES OF MACKINAC ISLAND AND THEIR RELATIONS TO THE 



LAKE HISTORY 



BY FRANK B. TAYLOB 



{Abstract) 



The old shorelines of Mackinac Island have been studied recently in much 

 more detail than formerly and have been placed on a large map with scale 

 of 200 feet to one inch and contour interval of 10 feet. The work is being 

 done by tlie Michigan Geological Survey and will be the subject of a report in 

 the near future. 



When mapped in this more complete way the beaches bring out with much 



