OUTLET TO MACKENZIE EIVEE IMPROBABLE. 231 



determined by marine fossils of the Champlain epoch and by the inclined 

 beaches of this glacial lake, ranged from no subsidence in the greater 

 part of Nova Scotia to probably 600 feet at Montreal, nearly the same at 

 Ottawa and about James Bay, approximately 500 feet in Manitoba, none 

 or little on the Mackenzie, and from 300 to 100 feet, probably decreasing 

 from north t(» south, on the shores of the Queen Charlotte Islands and 

 British Columbia. 



Some addition to these tigures, but probably nowhere exceeding a 

 quarter or tliird more, is required to give the earlier extreme extent of the 

 subsidence of the ice-weighted land, thus including its rise before the ice 

 above had wholly melted, or before the sea was admitted to Hudson and 

 James bays, and to the St. Lawrence, Lake Champlain, and Ottawa val- 

 leys. But this small added amount was oifset in part or entirely by the 

 effect of gravitation, which raised the levels of the ocean and lakes toward 

 the ice-sheet. These two causes of changing levels acted in conjunction 

 in their relationship to the series of shore-lines of Lake Agassiz, and to the 

 position and course of its oixtlets after it fell below the channel at Lake 

 Traverse; but the effect of ice attraction must be deducted from the total, 

 if we ask the extent of epeirogenic subsidence and reelevation, which there- 

 fore are probably closely expressed in the figures before stated, having a 

 maxinunn of 500 to 600 feet. 



Improbable h/fpothesis of cm outlet from Lake Af/assiz to the Mackenzie 

 Biver.—We mav therefore dismiss as untenable the supposition that the 

 outflow of Lake Agassiz, after falling below Lake Traverse and the Mc- 

 Cauleyville beach, and being still obstructed from going to Hudson Bay 

 by the presence of a large remnant of the ice-sheet there, could have 

 passed for a time across the divide between the Churchill and Athabasca 

 rivers, thus being discharged into the Mackenzie and the Arctic Ocean. 

 Such northwestward outflow would have crossed the present watershed 

 near the Methy portage, or by way of WoUaston or Hatchet Lake, which 

 has two outlets, one to the Churchill and the other to the Athabasca. The 

 altitude of the summit of the Methy portage, according to Richardson's 

 observations, with correction for the now better-known heights of Lake 

 Winnipeg and the Saskatchewan, appears to be about 1,750 feet above the 



