96 MAN AND THE GLACIAL PERIOD. 



extending through the northern part of Boone County, 

 Kentucky, and recrossing the river to Indiana, not far 

 from Rising Sun, it again follows approximately the north 

 bank of the river to within about ten miles of Louisville, 

 Ky., where it bends northward running through Clarke, 

 Scott, Jackson, Bartholomew, and Brown Counties to Mar- 

 tinsville, in Morgan County, where it turns again west and 

 south and follows approximately the West Branch of the 

 White River through Owen, Greene, and Knox Counties, 

 where it crosses the main stream of White River, and, con- 

 tinuing through Gibson and Posey Counties, crosses the 

 Wabash River near New Harmony. 



In Illinois the line still continues southwesterly through 

 White, Gallatin, Saline, and Williamson Counties, where 

 it reaches its southern limit near Carbondale, in latitude 

 3?° 40', and from this point trends northwestward, ap- 

 proximately following the northeastern bluff of the Mis- 

 sissippi River, to the vicinity of Carondelet, Mo., a short 

 distance south of St. Louis. 



Beyond the Mississippi the line follows approximately 

 the course of the Missouri River across Missouri, and con- 

 tinues westward to the vicinity of Manhattan, in Kansas, 

 where it turns northward, keeping about a hundred miles 

 west of the Missouri River, through eastern Kansas and 

 Nebraska, and striking the river near the mouth of the 

 Niobrara, in South Dakota. From there the line follows 

 approximately the course of the Missouri River to the vicin- 

 ity of Fort Benton, in northwestern Montana, where the line 

 again bears more northward, running into British America. 



It is still in dispute whether the ice extended from the 

 eastern centre far enough west to join the ice-movement 

 from the Rocky Mountain plateau. Dr. George M. Daw- 

 son * is of the opinion that it did not, but that there was 



* Transactions of the Royal Society of Canada, vol. viii, sec. iv, 

 pp. 54-74. 



