= 
Lieut. Ruggles on the Copper Mines of Lake Superior. 69 
presented, together with the lateral direction or bearing westward, 
and the associated semi-crystallized limerock, seem to prove incon- 
testably that this once constituted a bed or horizontal stratum at- 
tributable to aqueous origin, subsequently solidified—perhaps pu- 
rified—and elevated into its present position by volcanic or igne- 
ous action. 
It is also worthy of remark, that an extensive vein of calcareous 
spar, of a well characterized crystalline structure, is situated at 1, 
on the shore of Lake Superior, and is some eight feet in breadth ; 
and east of this about two miles} a similar vein of four feet in 
width is found. Now, if we assume that these veins, as well as 
the great number of a similar character holding the same general 
bearing, namely, S. 15° W., are attributable to igneous action, 
- under great pressure, analogous experiments prove that it is a ra- 
tional deduction. (See Hitchcock’s Geology, p. 244.) The con- 
clusion would therefore seem irresistible, that the Copper Harbor 
vein of black oxide was formed either under the pressure of wa- 
ter, or submerged during a long period after formation, when the 
metallic bowlders in question were driven from their original po- 
sition. In connection with this conclusion, I observe, that there 
is evidence of gradual elevation at remote periods, without corres- 
ponding subsequent depression. ‘The south shore of Lake Fanny 
Hooe appears to have been, upon its narrow margin, at one period, 
a regular beach, judging from its inclination and the composition 
of the detritus, which weuld have made the narrow isthmus 
where the fort now stands a sunken reef, as well as the arms 
of the present harbor, while the small lake must have been at one 
period a safe and commodious harbor amid the dreary waste of 
waters surrounding. In the present instance, the elements have 
placed a record within our reach, by which we can determine 
approximately that this region has found uninterrupted repose 
during along period past, and that the forces from which the 
present aspect and order of things resulted, are now held in equi- 
librium. We observe that a trap-dyke ranges and sinks in front 
of the landing at this post. (See fig. 1.) 2 ¢, is about 200 yards 
long, and a perpendicular from its centre strikes the shore at the 
distance of 100 yards. The east bank of Fort Wilkins creek has 
been swept away at least eighty yards inland from ¢, whilst the 
western bank of the same composition still remains entire—pro- 
tected by the dyke in front from the violence of the open road- 
