320 DESCRIPTION OF THE COUNTRY 
544), exposed just above the water-level; and about two miles further up stream is 
an exposure of mica slate (No. 545), bearing east by north and west by south. 
This last rock, like the granite, is exposed just above the water, and at neither 
place are rapids formed. Above this, the drift-hills increase in height to forty or 
fifty feet, and clay slides begin to appear in the river-banks. Just beyond the last 
exposure of rock is a rapid, and three hundred yards further up is an exposure of 
mica slate (No. 546), on the west side of the river, five feet high, and ten feet high 
on the east side. This rock is traversed by a dike of greenstone (No. 547), the 
bearing of which I did not ascertain. 
A short distance below the mouth of Opimabonowin River, the river-bed is 
composed of rock in situ; but its character could not be ascertained. Opima- 
bonowin River is about twenty yards wide at its mouth. It heads in the neigh- 
bourhood of Red Lake, and is sometimes called the West Branch of Big Fork River. 
About a mile above the mouth it is crossed by beds of gneiss, bearing northwest 
and southeast (Nos. 548, 549, 550). This, I was informed by persons in the 
service of the Fur Company, is the only exposure of rock on that stream. Above 
this point, rapids become more frequent on Big Fork River. The drift-hills also 
increase in height, some of them rising fifty and sixty feet above the river-level. 
About four miles above the mouth of Opimabonowin is an exposure of mica 
slate; and three hundred yards before reaching the Falls of Big Fork, greenstone 
was noticed in the river-bank. The mica slate referred to is traversed by granite 
veins, and forms a high ridge on the west bank of the river, trending in the 
direction of the mouth of Opimabonowin. 
_ The falls are about four and a half miles above the mouth of Opimabonowin 
River. Below them is a long rapid, and the river is wide and shallow. The first 
rock exposed at the falls, in ascending, is mica slate (No. 551), with large veins of 
coarse granite (No. 552) ramifying through-it. Where it comes in contact with 
the veins, the mica slate is very hard and compact, and becomes gneissoid in 
character. Next to the mica slate are beds of gneiss (No. 553), which, in a short 
distance, graduates into mica slate again (No. 554). Then comes an exposure of 
slaty greenstone (No. 556), which soon becomes compact. This last rock is 
traversed by a greenstone dike (Nos. 557 and 558), bearing east by north and west 
by south, which is also the bearing of the bedded rocks. Near the upper part of 
the falls, about sixty feet of slaty greenstone is exposed, which, as it recedes from 
the dike, graduates into mica slate. 
The fall at this place is twenty-nine feet in four hundred and ninety yards. In 
this distance there are five cascades. The channel is slightly winding, and narrow, 
not being over fifteen feet wide in most places. This is the highest point on the 
river to which sturgeon can ascend; and I was informed that great numbers are 
taken every season by the Indians, who encamp here for the purpose. 
Three-fourths of a mile above the falls is an exposure of mica slate (No. 560), 
rather more schistose in character than usual, and bearing, apparently, nearly 
north and south. 
For the next twenty-eight miles, according to my estimate, no rock was seen in 
place, the river-banks showing clay and sand beds, overlaid by a good soil, with 
