212 MAN AND THE GLACIAL PERIOD. 



an hour, and was felt three hundred miles down-stream, 

 destroying all the villages on the lower plain, and strew- 

 ing the fields with stones, sand, and mud.* 



In Greenland such temporary obstructions are fre- 

 quent, forming lakes of considerable size. Instances oc- 

 cur, in connection with the Jakobshavn and the Freder- 

 ickshaab Glaciers, and in the North Isortok and Alan- 

 gordlia Fiords. 



Frequently, also, bodies of water of considerable size 

 are found in depressions of the ice itself, even at high 

 levels. I have myself seen them covering more than an 

 acre, and as much as a thousand feet above the sea-level, 

 upon the surface of the Muir Glacier, Alaska. They are 

 reported by Mr. I. C. Eussell f of larger size and at still 

 higher elevations upon the glaciers radiating from Mount 

 St. Elias ; while the explorers of Greenland mention them 

 of impressive size upon the surface of its continental ice- 

 sheet. 



With these facts in mind we can the more readily 

 enter into the description which will now be given of 

 some temporary lakes of vast size which were formed by 

 direct ice-obstructions during portions of the period. 



One of the most interesting of these is illustrated upon 

 the accompanying map, which will need little description. 



While tracing the boundary-line of the glaciated area 

 in the Mississippi Valley during the summer of 1882, I 

 discovered the existence of unmistakable glacial deposits 

 in Boone County, Kentucky, across the Ohio Kiver, from 

 Cincinnati.]; These deposits were upon the height of land 

 550 feet above the Ohio Kiver, or nearly 1,000 feet above 



* Professor William M. Davis in. Proceedings of the Boston 

 Society of Natural History, vol. xxi, pp. 350, 351. 



f See National Geographic Magazine, vol. iii, pp. 116-120. 



% The existence of portions of this evidence had previously been 

 pointed out by Mr. Robert B. Warder and Dr. George Sutton (see 

 Geological Reports of Indiana, 1872 and 18T8). 



