i See 
Geology of Lake Superior. 11 
thinerals, and at others in grains very minute, and passing 
into greenstone. 
Neither gneiss nor micaslate was met with; although the 
granite, by an abundance of mica or a lamellar structure, may 
for a short space, sometimes assume the appearance of either. 
Seconv. The submedial order. 
In this order we noticed greenstone, common jasper, a 
variety of slates as greenstone, flinty chlorite and tal- 
cose slates, and, in one place alone, transition limestone. 
In one instance we think we observed traces ef greywacke, 
Tuirp. Trap or overlying rocks. 
These are very abundant. The most sois amygdaloid; va- 
rious kinds of porphyry are next in quantity ; then trap 
greenstone and sienite, (the former often basaltic,) and pitch- 
stone. 
Fourtu. The medial order. 
The only rock of this order is the old red sandstone, 
We shall now proceed to give a general idea of the rela- 
tive quantities of these rocks, and of their situation. 
11. Of the inferior order, sienitic granite, almost al- 
ways containing hornblende, (for which reason we adopt the 
term sievitic granite,) forms the highest hills; and it also 
either forms the shore, oris immediately in rear of it, from 
one extremity of the north coast to the other, thatis, from 
Gros Cap tothe St. Louis. It also forms the central parts 
of several of the large islands, such as Michipicoten Island, 
St. Ignatius Island, &c. 
It is also met with on the south coast, where it forms the 
nucleus of Point Keewawonan, and many hills from in 
rear of Granite Point to the Huron Islands, which last are 
also of this rock. The Porcupine or Wisconsan Mountains 
about 1500 feet above the lake, are also of granite. 
12, Submedial order. Greenstone. This is very abun- 
dant. It occurs in immense beds, forming perpendicular 
and 
