Geology and Mineralogy. | 409 
the nearest exposures of the parent rock, and to an elevation 
more than twice as great as that attained by any part of the 
Laurentian area. To explain this latter fact it seems now almost 
certain that we must assume that the western region was, in 
glacial times relatively to the Laurentian area more depressed 
than at present. As I have elsewhere, in the publications before 
r 
© P 
Hnudson’s Bay region, stretched continuo sly to the slopes of the 
cky Mountains, or such a gl , extending but a limited dis- 
u 
tance from these highlands, supplied numerous and massive ice- 
tgs which floated in a great inland sea occupying the present 
position of the plai 
h seems to give some 
color to the former hypothesis. This is the existence of a number 
of different parts of the district in post-glacial times : 
ren Upham has lately traced a number of such channels in 
Dakota (hypothetically extending his reasoning also t t 
glacier th : 
“In the southern part of the district of the present report, and 
particularly in the country south of the Belly River, great old 
Striki e 
Coulées and their tributaries. These resemble old river valleys 
long disused and now carrying little or no water. I am inclined 
ue t much 
greater depth and importance rapidly attained by the valleys 
carryi 
tain 
“In the entire obliteration of the original southeastward slope 
of the valleys of Verdigris and Pi-kow-ki Coulées, and other 
peculiar circumstances referred to in a previous part of this 
