OF THE ROCKS OF LAKE SUPERIOR. 959 
lumps; and it is probably analogous in its formation to the basaltic grits, its rela- 
tions being with the Anorthite and Palisade rocks, and its date cotemporaneous with 
the eruption of that rock. 
623. Bears, apparently, E. of N. This rock is very ferruginous, very crystalline 
in its aspect, and exhibits decided polarity. In its structure it has a somewhat 
schistose appearance, especially on exposed surfaces, and is most likely an overflow 
from a N. 30° E. dike of basalt. Colour, blackish gray, with a shining appearance. 
It is the same as No. 613, which resembles “ Nepheline rock,” and which bears E. 
and W. ‘The difference in bearing is easily accounted for, if it is a bedded rock, as 
it seems to be. Between the regular layers it is coated with oxide of iron, which 
gives that portion of the rock a thoroughly rusty appearance. It contains a great 
quantity of iron, and it is probable that it is from rock of this character that the 
ferruginous beds associated with the conglomerates have been derived. (See No. 
03.) 
624. Bears N. 45° W. Colour, purplish gray; fine granular; jointed. Com- 
posed of red felspar and black hornblende or augite. Resembles No. 618, but has 
more of a bluish tint. Magnetic. Smooth, conchoidal fracture. Bears most analogy 
to the N. and S. dikes. Weathered surfaces, black and smooth. Joints slightly 
incrusted with a zoolitic mineral, probably Heulandite. It is very compact, and 
shows no appearance of crystallization. Traverses No. 603 and No. 625. 
625. Bears N. 30° E. Resembles No. 603, and is probably a dolerite. Colour, 
dark greenish gray. Minutely crystalline, with occasional larger crystals of a 
greenish felspar (?) disseminated through it. Irregular fracture. Is more nearly 
like No. 615. Weathered surface black, somewhat irregular, but tolerably smooth. 
The joints contain thin incrustations of carbonate of lime. Magnetic. Minute 
scales of mica disseminated through it. Is traversed by No. 624. It may be com- 
pared with No. 613, but is less crystalline than this last-named rock. Belongs to 
the basaltic series; contains a great deal of deep olive-green mineral, soft, and 
having a lighter green streak. 
626. This specimen, which is from the bed of conglomerate which lies between 
the Palisade rock and No. 624, is a baked clay. It is of a rather light brick-red 
colour, shows traces of lines of deposition, and is somewhat amygdaloidal, the cells 
being very irregular in form, and compressed, with minute crystals of minerals, 
probably zeolitic, incrusting their sides. Has been much broken up and contorted 
by the intrusion of No. 624. Belongs to the lower shale-beds of the creek behind 
the Palisades. In some places the clay is discoloured, being dirty white or yellow, 
and in such instances is harder than the other parts of the rock. 
627. Metamorphosed slate, from the same breccia as No. 626. Very fine-grained. 
Colour, bluish gray—not unlike the altered slate at the Lower Falls of Pigeon 
River. (See Nos. 4 and 8.) In the joints of these fragments are incrustations of a 
green mineral, supposed to be epidote. The slate is amygdaloidal, the cavities being 
filled with calcareous spar, surrounded, in many cases, by a ring of chalcedony. Frac- 
ture irregular and jagged, and, in some directions, splintery. A ring of zeolite, in 
some of the cells, surrounding a nucleus of calcareous spar. 
628. Brecciated conglomerate—some of the fragments large, and of a deeper red 
