EXTENT OF THE IRON RANGE 109 



interruptions where covered with drift. Starting at little Gros Cap, it 

 runs about 20 miles to the northeast, then bending to the north and 

 west it takes a westerly direction for more than 30 miles. How much 

 farther it runs in that direction is unknown, prospecting having stopped 

 for the winter a few miles west of Dog river. The same association of 

 silicious rock and iron ore is found more than 70 miles farther west, near 

 Pic river, though it is not supposed that the range will be traced con- 

 tinuously to that point, for a tract of Laurentian is mapped as lying 

 between. Whether these rocks should be looked on as a continuation 

 of the Vermilion iron range north of lake Superior in western Ontario 

 and Minnesota and of the Penokee and Marquette ranges to the south 

 of the lake is not certain at present. Iron miners from Minnesota con- 

 sider it the same formation as the Vermilion range, and there seems no 

 reason to doubt that it was formed under very similar conditions and 

 shows many points of resemblance to that range. 



Sandstones of the same peculiar type occur at Little Turtle lake, east 

 of Rainy lake, and near Fort Frances, on Rainy river, as well as at the 

 Scramble gold mine, near Rat Portage, on lake of the Woods. Thin sec- 

 tions of these rocks show the same polygonal shapes of the grains of 

 quartz, and more or less iron ore is associated with specimens from each 

 locality. It is very probable, then, that the same horizon exists at points 

 far to the west of lake Superior. 



Turning toward the east, specimens very like the jaspery varieties of 

 the Michipicoton iron range are found interbedded with iron ores near 

 lakes Wahnapitae and Temagami, between Sudbury and the Ottawa 

 river. If, as seems probable, these jaspers are the equivalents of the 

 western Huronian sandstones, we have a definite horizon traceable from 

 point to point across the whole northern end of the province, a distance 

 of more than 600 miles. It is not suggested, of course, that these iron- 

 bearing sandstones and jaspers will be traced for this distance as a con- 

 tinuous band, for the Huronian areas are separated at several points by 

 tracts of Laurentian; nevertheless, if the conclusions just advanced are 

 correct, we have in these rocks a most valuable thread with which to 

 unravel the much disturbed and complicated series of the Huronian in 

 Ontario. 



The Dore Conglomerate 



Less than 2 miles north of the iron-bearing sandstone of Little Gros 

 cap there is a remarkable exposure of schist (or slate) conglomerate, ex- 

 amined many }^ears ago at the mouth of Dore river by Sir William 

 Logan, who evidently considered it a typical example of the Huronian, 

 since he has described it somewhat fully in his general account of that 



