20 Proceedings of the Ohio State Academy of Science 



The Geological Progress of Twenty-Five 



Years 



LEWIS G. WESTGATE. 



OUTLINE 



Introduction. 



The Study of Land Forms. 



Base-level, peneplain and erosion cycle. 

 Glacial Geology. 



The subdivision of the pleistocene. 



Former glacial periods. 



The cause of glacial periods. 

 The Interpretation of the Sedimentary Rocks. 



Fluviatile, lacustrine and marine deposits. 

 Paleogeograph Y. 

 Larger Problems of Geology. 



Continents and mountains. 



The planitessimal hypothesis. 



THE GEOLOGICAL PROGRESS OF TWEXTY-FR'E 



YEARS. 



INTRODUCTION. 



The feeling of elation which follows one's reception of the 

 news of his appointment to the presidency of an organization like 

 our own is hut momentary. It gives place almost at once to a 

 feeling of anxiety as one hegins to wonder what suhject he shall 

 choose for his presidential address a year later. In the present 

 case I have decided to depart from the custom of recent years, 

 of presenting a piece of research work, which is almost neces- 

 sarily technical in character, and to take a more general suhject, 

 in the hope that such a suhject may prove more interesting to 

 the societv as a whole : and I do this the more readily since the 

 majority of our members are biologists and not geologists. I 

 shall therefore speak of some of the advances which have been 

 made in the science of geology in the last twenty-hve years; for it 



