KELATION OF TOPOGRAPHY TO STRUCTURE. 435 



Lake slates. The factor of differential erosion was aided here by the strike 

 of the slates and the jointing, which agrees closelj'' with the strike of the line 

 of contact. Only in one place has any of the Lower Huronian slates been 

 left npon the north side of the main arm of the lake. Before reaching the 

 east end of this lake there is a large north-trending bay which is in Cana- 

 dian territory. The direction of this bay has been controlled, like that of 

 the main body of the lake, by the contact of the Lower Huronian slates 

 and the Archean formations which here swings sharply to the north. 



In the western part of the district, extending from Rice Bay of 

 Vermilion Lake, in T. 63 N., R. 15 W., over sec. 36, T. 64 N., R. 12 W., 

 over nearly to Basswood Lake, there is an almost continuous line of lakes 

 and streams marking the boundary between the Archean greenstone and 

 those schists which have been produced from this greenstone by the 

 metamorphic action of the Trout, Burntside, and Basswood granites upon it. 

 This line begins near Rice Bay, as mentioned above, and can be followed 

 east through the creek flowing into this bay from the east neai'ly to the 

 vicinity of Mud Lake in sec. 3, T. 62 N., R. 14 W. For a few miles then 

 it runs south of Burntside Lake. From sec. 32, T. 63 N., R. 13 W., it is 

 followed approximatel}^ by Burntside River up to sec. 24 of above township 

 and range. From there on to the east it follows approximately a string of 

 lakes — Little Long Lake, Bass Lake, and Mud Lake. Another striking 

 instance of this influence of the contact of two rocks on the topography is 

 shown in the case of the Kawishiwi River. Beginning in sec. 15, T. 63 N., 

 R. 9 W., where it enters the Vermilion district, it runs southwest very 

 closely along the contact between the gabbro and the Lower Huronian 

 sediments. Then when the sediments disappear it runs along the contact 

 between the Archean greenstone and Keweenawan gabbro, and where the 

 Griants Range granite commences it follows the contact between the gabbro 

 and the granite. Shortly after the granite is reached the Kawishiwi divides 

 in sec. 26, T. 63 N., R. 10 W., the south arm running southwest very closely 

 along the granite-gabbro contact. The north arm of the Kawishiwi continues 

 very nearly due west, following along the contact between the granite and 

 the schists produced by the contact action of the granite on the Archean 

 greenstone; then between the greenstone and the overlying Lower Huronian 

 sediments, and finally bends northwest, cutting across the greenstone. In 

 the eastern part of the district, in sees. 34 and 35, T, 65 N., R. 5 W., a string 





