522 THE GLACIAL LAKE AGASSIZ. 



temperature of this part of the earth's crust on account of the departure of 

 the ice woukl be practically insignificant in comparison with the direct 

 effects of the removal of the ice weight; and its small proportion in the 

 whole result would be to diminish instead of to increase its amount. Upon 

 this district, therefore, it seems well-nig-h certain that no other important 

 movement of elevation or of depression has taken place in connection with 

 that dependent on relief from the pre\nously existing ice load. 



But a fraction of the changes in the levels of this basin was due to 

 the diminution and final cessation of the ice attraction in its eff"ect to draw 

 water surfaces and the geoid level upward in the direction of the ice mass. 

 The proportion of this element may apparently have been as large as a 

 sixth or a quarter of tlie measured changes of levels; bvit its supposed 

 amount, so far as I am able to indicate it, is derived from estimates of the 

 volume of the ice-sheet, rather than from a discrimination of this part from 

 that due to elevation of the land. The two agencies of change were nearly 

 synchronous in their action upon the levels of the old shores, their effects 

 were distributed in the same manner in their relationship to time and space, 

 and both had almost ceased within this basin when the ice barrier of the 

 glacial lake was melted away. 



After progressively uplifting the area of Lake Agassiz, first chiefly in 

 its southern half and afterward mostly at the north, but nearlj- ending their 

 work here while the glacial lake yet existed, these agencies have since been 

 elevating the basin of Hudson and James bays. The latter part of their 

 labor remains unfinished, but during each century approaches considerably 

 toward its completion, which will fully restore equilibrium or isostasy to 

 this portion of the earth's crust. 



