OF THE ROCKS OF LAKE SUPERIOR. 243 
porosity renders it very light. Longer-continued or more energetic metamorphic 
agency, would probably have converted it into a rock like No. 117. 
389. A vein in No. 388—quartzose, granular; colour, dirty yellowish gray; fine- 
grained; a good many grains of felspar, and many of a green colour, too small to 
be determined ; has a banded appearance on fractured surfaces. A few small gravel- 
stones are contained in it. 
390. Metamorphosed sandstone—but little altered; colour, red; like the fine- 
grained argillaceous beds of the south shore of the Lake. Contains nests of quartz 
crystals. 
391. Dolerite—very fine-grained ; minutely crystalline; colour, very dark gray. 
Weathers with a smooth, light-gray surface, covered with a thin crust. Sometimes 
the weathered surface is black. 
392. Basaltic rock—colour, gray ; homogeneous; shows no appearance of crystal- 
lization; fracture, even, inclined to be conchoidal. 
393. A seam ‘at the junction of Nos. 390 and 391—contains angular fragments of 
No. 391, the interstices being filled with calcareous spar and zeolites. One side of 
the seam appears to have been rubbed smooth by a vertical motion. 
394. Amygdaloidal nests in No. 390—the cells filled with globular and kidney- 
shaped nodules of calcareous spar, the nodules being incrusted with a thin coating 
of green carbénate of copper. Some of the cells are filled with carbonate of copper, 
and a few grains of the same mineral are scattered through the base of the amyg- 
daloid. 
395. Tourmaline—in nests in No. 390; colour, brown and brownish red; in 
long crystals, penetrating calcareous spar. Many of the crystals are green exter- 
nally. 
396. Quartz crystals—in druses in No. 390; some of them are large, and all are 
incrusted with oxide of iron. 
397. Epidote—associated with calcareous spar ; in metamorphosed sandstone con- 
glomerate. 
398. Vein in metamorphosed sand-rock—resembles No. 389. Contains native 
copper and prehnite, with numerous grains of native copper disseminated through 
it. The veinstone is quartzose. 
399. Has a syenitic appearance—but is probably a volcanic tufa; colour, red; is 
made up of fragments of felspar and hornblende crystals, enveloped in a very calca- 
reous paste. 
400. A tolerably fine-grained calcareous rock—highly metamorphosed ; resembles 
aphanite; contains fragments of clay-slate. 
401. Metamorphosed siliceo-calcareous shale—amygdaloidal; colour, purplish gray ; 
belongs to the amygdaloidal earthy beds. The cells are filled with carbonate of 
lime in kidney-shaped nodules, with a thin coating of chlorite next the sides of the 
cells. 
402. Argillo-caleareous shale, highly metamorphosed ; amygdaloidal ; cells nume- 
rous, and filled with carbonate of lime; colour, purplish gray; decomposes easily, 
when exposed to the weather. This rock is associated with a syenitic-looking tufa- 
ceous porphyry, which contains much flesh-coloured felspar, in irregular, fragmen- 
