33^ ^- E- CAMERON 



The area to be discussed is shown in the accompanying map 

 (Fig. i). It hes between latitudes 56° north and 63° north, longi- 

 tudes 107° west and 120° west, and it comprises the lower portions 

 of the valleys of Peace and Athabaska rivers, Athabaska Lake and 

 Great Slave Lake. 



Tyrrell,^ in his report on Athabaska Lake and Churchill River, 

 makes frequent reference to the great post-glacial lakes of this 

 region. He says: 



North of the watershed between Churchill and Stone rivers, most of the 

 akes appear to have stood at a higher level than they do at present, in the 

 time immediately subsequent to the retirement of the great ice-sheet. The 

 natural inference is that they lay between the face of the waning ice-sheet and 

 higher land over which the water flowed to form the great rivers of the glacial 

 period. 



He proposed the addition of the prefix "hyper-" to the name of 

 the present lake or river to designate the former high-level lake that 

 occupied its basin or valley. 



Tyrrell's report covers the area east of Athabaska River and 

 south of Athabaska Lake, and is therefore in part included in the 

 region under discussion. Certain parts of his reports are of prime 

 importance in any consideration of the question. Particular refer- 

 ence must be made to his Hyper-Black Lake, Hyper-Athabaska 

 Lake, and Hyper-Churchill Lake. Black Lake Hes directly east of 

 the eastern extremity of Athabaska Lake and is connected with 

 Athabaska Lake by a broad, trenchlike valley at present occupied 

 by Stone River. Tyrrell says: 



Hyper-Black Lake stood 125 feet above the present level of Black Lake, 

 and extended for a long distance up Cree and Stone rivers. Hyper-Athabasca 

 Lake rose above the present level of Lake Athabasca, as is shown by the 

 beautiful raised beaches on Beaver-lodge Island, and the wide sandy plains 

 seen by Mr. Dowling on William River; but whether it at any time was 

 confluent with Hyper-Black Lake was not determined Hyper- 

 Churchill Lake lay in the present valley of Churchill River, and, when at its 

 greatest height, seems to have extended southward as far as the sand-hills 

 around Clearwater Lake on the Green Lake trail. 



'J. B. Tyrrell, "Athabasca Lake and Churchill River," G.S.C. Annual Report, 

 New Series, Vol. VII, "D," 1895. 



