BEACHES OBSERVED BY ME. TYRRELL. 219 



and the total length of the glacial lake, then near the middle of its entu'e 

 time of northeastward outflow, was more than 500 miles, with probably 

 one-third as great width in its northern part. The amount of upward 

 tilting toward the north upon the area extending 150 miles from Gladstone 

 to Kettle Hill since the Grladstone beach was formed has been 40 or 45 

 feet. About twice as much tilting had occurred there between the times 

 of formation of the Hillsboi'o and Gladstone beaches as since the date of 

 the later one of these shore-lines. Lake Agassiz in its Gladstone stage 

 had become reduced probably to half of its earlier maximum extent. 



Mossy poi'tage, between Lake Winnipegosis and Cedar Lake, is about 

 60 miles northeast of Kettle Hill; and the Grand Rapids of the Saskatche- 

 wan, near its mouth, are about 25 miles farther east. Both these localities 

 are nearly on latitude 53° 10' north, being- some 50 miles north of the 

 latitude of Kettle Hill and 285 miles north of the international boundary. 

 The summit of the eastern Mossy portage is described by Mr. Tyrrell as a 

 gi'avel ridge with crest 93 feet above Lake Winnipegosis or 921 feet above 

 the sea. It is doubtless a beach formed by Lake Agassiz when it stood 

 here at the level of about 910 feet. Descending southward to Lake Win- 

 nipegosis, the portage crosses another beach ridge with its crest 27 feet a^d 

 its base about 15 feet above this lake, and it is therefore clearly referable 

 to a level of Lake Agassiz about 845 feet above the sea. These stages of 

 the glacial lake are quite surely the same which made the Burnside and 

 Stonewall beaches near the south end of Lake Manitoba and the city of 

 Winnipeg. An escarpment crossed by the portage midway between these 

 beach ridges appears to mark the position of the intermediate Ossowa shore. 



The Burnside lake level reached south in the Red River Valley to 

 Grand Forks, and had an entire length of nearly 500 miles thence to the 

 latitude of 55° north, with a width from 150 to 175 miles in its northem 

 half Above the southern end of Lake Winnipeg the depth of Lake Agassiz 

 at this stage was 150 feet, and above its northern end aliout 200 feet. 



The next lower level of Lake Agassiz, which is recorded by the Ossowa 

 shore-line, lacked only 15 miles of reaching to Grand Forks, and had almost 

 as great total length and widtli as the preceding. Its height above the 

 south ends of Lakes Manitoba and Winnipeg was about 30 and 130 feet, 

 respectively. 



