G. F. Wright — Continuity of the Glacial Peinod. 183 



facts bearing upon the question in hand. Notwithstanding the 

 general excellence of the report, we are not sure that we have 

 been able altogether to ascertain the personal equation of the 

 writer ; for in many places it is evident that slenderly sup- 

 ported inferences are stated with such an unwarranted degree 

 of confidence as is calculated seriously to mislead the unin- 

 formed reader. This is specially the case in the part which he 

 has assigned to the Pleistocene water bodies. Repeatedly in 

 his maps he covers the driftless area of Wisconsin with a body 

 of water produced by the damming up of the Mississippi 

 through the junction of the lobes of ice which came down from 

 either side. This he has named Lake Hennepin. I have not 

 much personal familiarity with the region ; but, judging from 

 the explicit reports upon it by Professors Chamberlin and 

 Salisbury, they would seem to be correct in discrediting the 

 existence of any such body of water. I am more familiar with 

 the region in Indiana between the forks of the White River, 

 just south of the moraine — a region which I explored somewhat 

 carefully ten years ago. This is the highest land in the State, 

 running up in one place to an elevation of 1147 feet above 

 tide, and the whole country to the south of it was open during 

 the glacial period.* In short it is an impossible position for a 

 Glacial lake. Yet Mr. McGee has it covered with a Pleistocene 

 body of water. 



Nevertheless, this tendency to theorizing independent of the 

 facts may not be allowed to discount the great body of Mr. Mc- 

 Gee's observations which bring to light several very important 

 things. We note in the first place, that, while the sixteen thou- 

 sand square miles in Northeastern Iowa upon which he reports 

 lies entirely outside of what Professor Chamberlin had reckoned 

 as "the terminal moraine of the second Glacial epoch," yet 

 Mr. McGee insists that the area is covered by the remains of 

 two Glacial epochs, separated by an interglacial period, which 

 is rather indefinitely reckoned as from 28 to 280 times as long 

 as the period of written history, that is from 200,000 to 2,000,- 

 000 years in extent, if by written history he includes the writ- 

 ings upon the monuments in Egypt and Babylonia. 



Secondly, the principal basis of this inference is the existence 

 of a forest bed over a portion of the area near the margin, and 

 a marked difference between the character of the upper and 

 lower tills. 



But, thirdly, the character of the vegetal deposits does not 

 indicate as warm a climate as that which now characterizes the 

 region ; but, like those in Southern Ohio, which Professor 

 Orton and Mr. Leverett have described, the interglacial trees 



*See map, Fig. 1. 



