NORTHWEST SHORE OF LAKE SUPERIOR. 375 
of volcanic grit (No. 162), extending along the bank for fifty yards. It is in near 
contact with a dike, and appears to be composed in part of basaltic material. The 
blocks which fall from the escarpment weather into rounded masses, very like those 
found in the beds of globular basalt. The following sketch, by Major R. Owen, 
exhibits the exposure at this place. 
VOLCANIC GRIT AND BASALT, INAONANI RIVER, 
In ascending the river* immediately after leaving the mouth, Nos. 163 and 164 
come up, dipping to the southeast, at an angle of 29°, and forming mural precipices 
between forty and fifty feet in height. A quarter of a mile above, No. 165 is the 
top rock, and four hundred yards further there are several beautiful cascades, making 
a fall of one hundred and six feet in the distance of one hundred and twenty yards. 
Some of the cascades have a nearly perpendicular fall of twenty feet, while at 
others, the water flows down inclined planes. The grit-beds alternate with shales 
at the head of the cascades, and dip southeast 13°. 
About a quarter of a mile above the cascades the rock becomes harder, more 
compact, less amygdaloidal, and contains nests of prehnite (No. 166). The dip is 
here east-northeast 13°. Two hundred yards further on is a plateau, rising from 
ten to twelve feet above the river, made by No. 167. Through this rock a dike of 
No. 168 has been erupted. As the dike is approached, No. 167 assumes the cha- 
racter of No. 169. Halfa mile further on, the dip changes:to southeast, and four 
hundred yards further, the rocks are overlaid by clay and marl beds, about sixty 
feet thick. The rocks are concealed for the distance of three hundred yards, when 
they are exposed in the east bank of the river in ledges from eight to ten feet high. 
Nearly a quarter of a mile above this point, there is a ridge composed of No. 170, 
crossing the river, and containing large masses of No. 171. This is the same rock 
seen at the mouth of Kawimbash River, and at many other localities in this region. 
The ridge is about five hundred yards wide, and the river cuts directly through it, 
* See Section from the mouth of Inaonani River northwesterly. Pl. 1 N, Sect. 6. 
