20 Proceedings of tJie Ohio State Acadciny 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. 

 Paleogeography. 

 Larger Problems of Geology. 



Continents and mountains. 

 •The planitessimal hypothesis. 



THE GEOLOGICAL PROGRESS OF TWENTY-FIVE 



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 but momentary. It gives place almost at once to a 

 feeling of anxiety as one begins to wonder what subject 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 subject, 

 in the hope that such a subject 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-five years ; for it 



