THE GLACIAL HYPOTHESIS 319 



strated: (1) An age of general elevation of northern land, accompanied 

 by intense cold and the formation of extensive continental glaciers; 

 (2) a general depression of the land, with the return of a milder cli- 

 mate; (3) a partial reelevation of the land and a partial return of the 

 cold climate, producing local glaciers and icebergs. 



E. T. Cox, while state geologist of Indiana, encountered phenomena 

 in every way similar to those described by Newberry and Orton, and it 

 is to be expected that his mode of accounting for the same would be 

 somewhat similar. In his report of the conduct of the survey of that 

 state (1869-79) he announced his acceptation of the general theory 

 of glacial drift, as at that time understood, and conceived that the 

 necessary climatic changes might be due to the relative position of land 

 and water, and, possibly, a change in the course of the Gulf Stream. 

 He could find, however, no evidence of a subsidence of the land to 

 terminate the glacial period, nor could he find in Ohio, Indiana or 

 Illinois anything to militate against the commencement of the glacial 

 period in Tertiary times and its continuation until brought to a close 

 by its own erosive force aided by atmospheric and meteorological con- 

 ditions. By these combined agencies acting through time the moun- 

 tain home of the glacier was cut down and a general leveling of the 

 land took place. This suggestion that the glacial epoch worked out 

 its own destruction through a process of leveling, whereby the altitudes 

 which gave it birth were so far reduced that glaciers could no longer 

 exist, is unique and, so far as the present writer is aware, original 

 with Cox. 



The organization in 1876 of a state geological survey of Wisconsin 

 afforded Professor Chamberlin and his assistants opportunity for in- 

 vestigation of the drift phenomena of that state, and in the pages of 

 his reports his views are distinctly formulated. He divided the glacial 

 period into: (1) The terrace or fluviatile epoch, (2) Champlain or 

 lacustrine epoch, (3) the second glacial epoch, (4) the interglacial 

 epoch and (5) the first glacial epoch. This formal announcement of 

 the possibility of two distinct periods of glaciation was here made for 

 the first time, although, as before noted, Edward Hitchcock had at 

 an earlier date suggested such a possibility. 



Not content with a mere discussion of the glacial phenomena, 

 Chamberlin considered also matters relating to the cause of glacial 

 movement. The law of flowage he announced as being, in his opinion, 

 similar to that of viscous fluids — this in accordance with the observa- 

 tions of Agassiz, Forbes, Tyndall and others. A later study of Green- 

 land glaciers, as is well known, has caused him to change his views on 

 this point. 



In the third edition of his work on ' Acadian Geology,' which ap- 

 peared in 1878, J. W. Dawson returned once more to a vigorous dis- 



