800 



ANNUAL BEPORT SMITHSONIAN INSTITUTION, 1912. 



not known in any other part of the world. The total area covered by 

 their waters from first to last was much greater than the entire area 

 of the present Great Lakes, but the whole area was not covered at 





M p5 



any one time. Only one glacial lake of larger size is known to have 

 existed; this is Lake Agassiz, which overspread northwestern Minne- 

 sota, northeastern North Dakota, and a great area in Manitoba and 



