THE LESTER RIVER BEDS. 279 
Duluth rocks, to whose horizon it may reasonably be referred. The rocks 
of the upper Cascade River, and the east end of the Minnesota coast, which 
may belong in part to the member now under description, are considered 
after the next two members are described. 
The Lester River Group—The third member of the succession on 
the Minnesota coast I have divided from the second by a rather arbitrary 
line. Its beds were seen best exposed on the lake shore from a point be- 
tween Chester and Tischer’s Creeks, in Sec. 24, T. 50, R. 14 W., to a point 
about two miles below the mouth of -Lester River, in Sec. 34, T. 51, R. 13 
W.; along Lester River, and in the woods west of the river, in Sees. 4 and 
5, T. 50, R. 13 W., and Secs. 29 and 33, T. 51, R.13 W.; along French 
River, in Sees. 6 and 7, T. 51, R. 12 W.; in scattering ledges in the woods 
in the southern part of T. 53, R. 11 W., north of Knife River; and again 
along Encampment River, in Secs. 3, 10, and 11, of T. 53, R. 10 W. 
This group is made up chiefly of beds of fine-grained to nearly black, 
dark-gray, brown, or reddish-brown compact rocks, occasionally porphy- 
ritic with reddish plagioclases; but this character is not so marked as in 
the preceding group. No detrital material was observed, and only one or 
two amyedaloids, although feebly developed pseud-amygdaloids occur more 
frequently. A few coarse-grained beds are included, and there are two or 
three belts or areas of red granitic porphyry. Several narrow dikes were 
seen on the coast, like those of the Duluth Group, and, like them, trending 
with the general direction of the beds, now altered from what it was near 
Duluth. 
The prevalent fine-grained beds were best seen on Lester and French 
Rivers. At the mouth of Lester River and for some distance below, and 
again up the river for half a mile, are large exposures of a very fine- 
grained, dark-brownish to dark-greenish, compact, very heavy rock, with 
a few minute porphyritic feldspars. The chief constituent is a plagioclase, 
in minute tabular crystals, which never give higher angles than for oligo- 
clase. Quite subordinate in quantity are the minute particles of augite, 
many of which are largely altered to a greenish substance, with which is 
also associated more or less magnetite, evidently as a product of alteration. 
