TEMPERANCE RIVER GROUP. 323 
of the dike suggest that we have here its original top. The rock of the 
dike is a very dense, dark greenish-gray diabase-porphyrite, with a tendency 
to become somewhat coarser in the middle. The silica content of this dike- 
rock is very low, being only 45.88 per cent. The whole dike is intersected 
by two sets of very strong transverse joints, which dip respectively S 134° 
and E. 694°. These are cut by others parallel to the walls of the dike and 
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Fia. 25.—Dike in quartz-porphyry, Red Rock Bay. 
the whole mass looks much like a pile of books. About one-fourth of a 
mile farther down the coast another dike, of more completely crystalline 
diabase, cuts the red rock, which soon after ends, being replaced by the 
rocks which I have already described in connection with the Duluth and 
Lester River groups. 
Temperance River Group.—The rocks of this group are displayed along 
the coast from a point a mile and a half below the mouth of Baptism River 
to Grand Marais, a total distance of some 50 miles. The total thickness 
appears to be upwards of 2,000 feet. The highest beds of the group 
form the coast between Petit Marais and Temperance River. As already 
described, the beds of this group, where they first appear in descending the 
coast, just below Baptism River, trend sharply to the north, and even due 
north for a while, after which they swing around more to the east of north, 
the coast line and strata trending together for a long distance. 
The easting in the trend of the layers continuing to increase at about 
two miles below Temperance River, they finally begin to trend more to 
the east than the coast line, so that from this point to Grand Marais, 
