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Mountain.’ Test pits are common where it outcrops, and at 
Amasa it contains iron in quantities sufficient to be mined. This 
series is also characterized by its marked magnetic properties. 
It was chiefly due to this property that it was found possible to 
connect the widely separated outcrops by means of the dip 
needle and of the dial compass. 
The entire district is heavily covered with drift, showing in 
many places beautifully developed glacial topography. This 
mantle conceals so much of the country rock that the outcrops 
are very scarce, thus very greatly increasing the difficulties of the 
geologist. 
Owing to the incompleteness of the work the structure of the 
area and the correlation of its rocks will be left for a future 
report. It can be stated, however, that the volcanics are of 
Huronian age. 
Volcanics.—Vhose discussed in this paper lie in general to the 
west of the Archean core, and between Bone Lake on the north 
and Crystal Falls on the south. They are the rocks which pre- 
dominate in, and are by far the most characteristic for, this dis- 
trict, the sedimentaries playing only a very subordinate role. 
The belt in which they are found varies in width from three- 
fourths to four and one-half miles. The apparent enormous 
thickness which this would give to the series in the widest part of 
the belt, since the dip of the rocks is about 75°, has been greatly 
increased by the minor crumplings and thrusts to which the 
series has undoubtedly been subjected. The very considerable 
thickness may be partly explained by supposing the volcanics to 
have accumulated in the immediate proximity of the vents from 
which they were ejected. If we accept an average thickness of 
4000 feet, we will probably not overestimate it. 
Since the flows are all now on edge, and erosion has left only 
isolated fragments of flows and accompanying tuffs, it is only 
possible to study them in cross section. Owing to this fact the 
topography is very rough, the elevations in most cases corre- 
sponding to the massive rocks, though thoroughly consolidated 
breccias form some of the highest hills. That these rocks are 
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