68 Lieut. Ruggles on the Copper Mines of Lake Superior. 
closely to that of cast iron. 'The conclusion is therefore evident, 
that present causes* combined cannot, by any possibility, have 
produced such aresult ; and that it is attributable to the agencies 
of the great diluvial or drift period, or those of subsequent action, 
and which have long since reposed in equilibrium. If we sur- 
vey the geological aspect of the surrounding district, the indica- 
tions of causes sufficiently powerful meet us on every side. A 
species of well characterized trap-conglomerate extends west- 
wardly along the southern coast to the head of Lake Superior, 
also several miles inland, embracing an area, probably, unparal- 
leled in the history of this formation. This stratum is composed 
of pebbles and small bowlders of every variety and description, 
cemented by calcareo-siliceous matter firmly solidified, disclosing 
clearly defined traces of ancient igneousaction. On the elevated 
range south of the small lake, where: the mother trap appears, 
the conglomerate has been ruptured along its longitudinal axis, 
and pitched outwards, and even now displays the ragged faces of 
large masses once violently fractured. But in the vicinity of the 
lower trap dykes, the disruption of the conglomerate has in a 
great measure disappeared under the ancient abrasion of incumbent 
waters, while the rock was still comparatively soft—from the 
elements of which a partial re-arrangement resulted. ‘Thus re- 
markable inequalities in the thickness of this stratum have arisen. 
The numerous trap dykes and traversing fissures, as well as the 
peculiar tinge of the new red sandstone, disclose unerring indica- 
tions of a remote period of volcanic or igneous action. There is, 
also, in this vicinity, a remarkably well characterized straiwm or 
bed of black oxide of manganese. It crops out in the precipitous 
bank of the creek leading from Lake Martha Stevenson to Lake 
Fanny Hooe, at g. (See fig. 1.) An extent of some sixty feet 
is developed, and is about two feet in thickness; it is compact, in- 
termixed with and disseminated through a pearly, semi-crystalline 
calcareous spar. The stratum runs in a lateral direction, and the 
crop ranges at an angle of at least 45° with the horizon, parallel 
with the course of the creek and perpendicularly to the axis of 
the mother trap range, over which it doubtless lies. The undu- 
lating appearance of the crop, the high angle under which it is 
* The author doubtless intends by “ present causes,”’ those that are now operating 
under existing circumstances, in that region; he doubtless admits that the causes, 
whatever they have been, are still existing, and elsewhere in action. —Eps. 
ag 
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