. 
20 Messrs. Foster and Whitney on the 
river, a highly crystalline mass of this charaeter emerges in the 
orm of an island fifty or sixty feet in height. 
The main Presqu’isle consists of a dark-green trappean rock, 
rising in the overhanging cliffs to the height of a hundred feet. A 
description of this rock and the relations which it bears to the sand- 
stone will be given when we come to treat of the Silurian system. 
Over this is deposited a volcanic tuff, imperfectly stratified, filling 
up the previous depressions, and attaining a thickness of twenty 
or thirty feet. It presents a complete net-work of veins, a few 
lines only in width, which penetrate but a short distance into the 
subjacent basalt. At one place, on the northwest side of the point 
an irregular vein bearing north and south is seen for two hundred 
feet in a linear direction, in this obscurely stratified tuff, which 
yields the sulphurets of lead, copper and iron, but not in sufficient 
quantities to render its exploration profitable. Asbestus is also 
sparingly distributed, and may be regarded as a metamorphic 
product resulting from the presence of lime. ‘Traces of mag- 
netic oxyd of iron are detected in some of the veins farther 
eastward. 
Proceeding up the valley of Dead River, between sections 7 
and 18, township 48, range 25, the stream is precipitated from a 
height of twenty feet over a ledge of schistose rocks, which ex- 
hibit distinct lines of bedding and abrupt convolutions of the 
Strata. 
In the next range west (27) the trappean and schistose rocks 
are frequently exposed in the bed of the stream, consisting of al- 
ternations of talcose and chlorite slates, and hornblende and feld- 
spar rocks. ‘They stretch out in numerous parallel ridges, bear- 
ing north of east and south of west, and present, for the most part, 
southerly escarpments. On the northwest quarter of section 16, 
the river is precipitated in a series of rapids over the former class 
of rocks, affording fine exposures for observation. On the west 
boundary of section 6, in a high ledge which rises from the 
northern bank of the stream, the slates are again observed 
dipping to the south at an angle of 70°, 
The stream here bears west-northwest, conforming to the 
direction of the strata. After flowing along the northern line of 
township 48, nearly through range 27, it divides into numerous 
branches whose sources lie to the northwest, in the region of the 
granite. 
Proceeding southward from Teal lake, we first encounter @ 
magnetic oxyd of iron. As we shall devote a special chapter to 
the character of these masses and their relations to the associated 
rocks, a more minute description is here deemed unnecessary: 
4 
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