1852.] OF THE ROYAL INSTITUTION. 161 
formed in agitated seas between eruptions ; —at different and most 
probably distant times, judging from the fact that some of the conglo- 
merates are altogether trappose, while others abound in granite and 
other bowlders. 
We thus obtain the general order of all these events, and little 
more; but the knowledge is worth having. From the position of 
the up-lifted mural cliffs, we see that the upheaving impulse came 
from the south-east. 
Drift. The groovings and striz are almost always northerly here. 
New proofs are daily accumulating to shew still more decisively 
the northerly origin of the foreign drift of Lake Superior. One of 
these is the fact that the limestone bowlders on the north shore are 
upper Silurian,* and derived from the large calcareous basins some 
hundreds of miles north of Lake Superior: from whence Dr. B. had 
brought characteristic fossils. Another is found in the occurrence 
of bowlders of iron ore, in heaps, on the north side of certain cliffs, 
but which are absent on the south side —the original site of the 
ore, being to the north of the cliffs, and near Lake Superior. 
A Sketch was exhibited of a Wisconsin prairie, dotted with northern 
blocks dropped from icebergs.—From Dr. D. Owen. 
Commercial Resources. — Agriculture will only be carried on in 
parts of the south shore. Large quantities of white fish, and of furs 
are annually exported. 
The chief staple of Lake Superior is native Copper. For ages 
before the appearance of Europeans in America, this metal was 
supplied from hence to the Indian nations far and near. The tumuli 
of the Mississipi, &c. contain the identical copper of this lake. 
Traces of ancient mining in Keweenaw, Ontonagon, and Isle Royale 
are abundant, in the form of deep pits (a ladder in one), rubbish, 
stone mauls, hammers, wedges, and chisels of hardened copper. 
In a native excavation, near the river Ontonagon, with trees five 
hundred years old growing over it, lately lay a mass of pure copper 
81 tons in weight, partly fused and resting on skids of black oak. 
Modern explorers have hitherto only found two centres of metallic 
riches on the south coast, — that of Keweenaw and of Ontonagon. 
In the first are the valuable mines of the Cliff, North American, 
North-western and other companies. In the Ontonagon centre is 
the Minnesota and fifteen other mines. 
At the Cliff mine three large steam engines are employed (1852) ; 
with 250 men ;—and at the North American mine, two engines, 
with 160 men. Most of the other mines, forty in number, are 
assisted by steam power. Three thousand miners are in work 
altogether, and the general population is fast increasing. Native 
copper is the principal object. Silver is always present, and occa- 
sionally in masses of considerable size. According to authentic 
* Containing Pentamerus, Spirifer, Lepteena (alternata) atrypa, various corals, 
minute trilobites, orthocerw, and some cytherine. 
