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 2, 
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 would 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 a long 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.) m ¢, is about 200 yards 
long, and a perpendicular from its centre strikes the shore at the 
distance of 100 yards. Theeast 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- 
