384 J- T. PARDEE 



of this region was then the same as now. This is for the purposes 

 of argument assumed to be essentially true, such crustal warping and 

 modification of the surface by erosion as have occurred during or 

 since that time being, as indicated by the evidence at hand, insufficient 

 to have seriously altered the topography of this region. 



The evidence of icebergs, together with the apparent recency of 

 the lake and the variable height of its surface, connect this lake with 

 the glacial period, and readily lend themselves to the suggestion that 

 its dam was of ice. 



Bailey Willis has suggested that this was a Pleistocene lake 

 dammed by a glacier.' Many years ago Professor Chamberlin con- 

 ceived the idea of a glacial dam and furthermore tentatively suggested 

 that its location was in the Pend d' Oreille region with outflow by way 

 of Spokane.^ 



While there has been some local glaciation in the Cceur d'Alene 

 and Cabinet mountains^ it is evident that these small glaciers were 

 inadequate to have themselves formed the dam, although they may 

 have aided in its production. 



That British Columbia was formerly buried under a vast accumu- 

 lation of ice, generally referred to as the Cordilleran ice-cap, has been 

 made known by the writings of Dawson and others. It appears that 

 south-flowing portions of this ice-cap were even at the 49th parallel 

 of great depths. ^ Its margin was markedly lobate, south-flowing 

 tongues having occupied every large valley that crosses the Interna- 

 tional Boundary between the Cascade Mountains and the continental 

 divide. To this ice invasion the "trenches" characteristic of this 

 region owe, in a certain measure, their form and fairly constant 

 depth. 



While the limits of these great valley glaciers which crossed the 

 boundary west of the Idaho panhandle are fairly well known, knowl- 

 edge of those east of that point is more or less fragmentary. Some 



1 Earl Douglass, The Neocene Lake Beds of Western Montana, published by Mon- 

 tana University, 1899, 11. 



2 Personal communication. 



3 F. L. Ransome and F. C. Calkins, "The Geology and Ore Deposits of the 

 Cceur d'Alene District, Idaho," Professional Paper, U.S. Geol. Survey, No. 62, 15, 

 57; and F. C. Calkins, op. cit., 15. 



4 R. A. Daly, Can. Geol. Survey, Summary Report , 1903, 93; ibid., 1904, 95. 



