R. Irving—Copper-bearing Rocks of Lake Superior. 55 
The arguments in favor of these views are as follows: 
Ist. The belt of rocks forming the southerly side of this 
synclinal is known to continue far westward into Wisconsin. 
It is therefore to be suspected that the northerly side has a 
similar extent. 
2nd. If this northerly side does continue westward, it must 
be entirely under the waters of the lake, or on the southern 
shore, since on the northern shore the rocks are altogether 
different. 
3d. This westerly continuation of the northerly side would 
preserve some sort of parallelism to the southerly side. 
4th. The peninsula of Bayfield, Isle Royale, and Keweenaw 
Point have the same general trend. 
5th. The copper-bearing melaphyres, &c., of Douglas and 
Bayfield Counties dip, wherever the dip is observable, to the 
southward. 
6th. The northerly dip of the beds of the Keweenaw Point belt 
gradually increases in degree as the rocks are traced westward 
from Keweenaw Point, where it is low, until the Wisconsin line is 
reached, where it is vertical. This being the case, it would be 
expected that the two sides of the synclinal would approach 
one another in their western extension, which is in accordance 
with the facts, whether the southward-dipping sandstones be 
regarded as marking the northerly edge or not. : 
7th. If the supposition be true, then, on the northerly side 
where all the observed dips are from 25° to 38°, the area of 
country immediately underlaid by the pia pe edges 
would be much broader than on the southerly side where the 
* The low dips—25°—observed in some places, would go to confirm the first of 
