430 Brooks and Pumpelly—Age of the 
Again, there are at least two patches of sandstone lying on 
the upturned melaphyre beds near Houghton, though it was 
not easy to prove that they were not brought thither by glacial 
action. Mr. Alexander Agassiz informs me that he has found 
in the horizontal sandstones near this so-called “ fault,” abun- 
dant pebbles of the melaphyre and conglomerate of the Cuprif: 
erous series. d 
Sir William Logan hints at a similar doubt as to the proxi- 
mate equivalence in age of these two series of rocks.* Durin; 
last autumn, traveling sometimes together and sometimes apart, 
we made a reconnaissance of the country between Bad river in 
Wisconsin and the middle-branch of the Ontonagon, east of 
Lake Gogebic+ in Michigan. Our route was chiefly confined 
to the surface of the upper member of the Michigan Azoi 
which we have provisionally considered to be the equivalent of 
the Huronian. 
? ‘ i) ee laa a se Sate 
Fa OY See a ete ae aT ee GN es Ones SCR res yo a a eT eS ee eee ee ee ee 2 I 
Keweenaw Point. Between these two ranges lies the — 
western part of the Silurian trough, which has been mention 
0°.t But in approaching Lake Gogebic from the west, W® 
find that erosion of Silurian or pre-Silurian age has made 4 
of 
* Geol. of Canada, page 85. And again in Geol. Survey of Canada, a ogly 
Progr. 1866-69, pp. i341 5. In the last mentioned place, he protests. 5 
ba Be ee that the copper-bearing rocks of Lake Superior are Triassi¢ 
rongly written A bic on many maps. wie 
} We observed several d dips in the fruvoulid of 25°-40°, while in ee! at “i 
lying Cupriferous series none lower than 50° were found. While this ph oe 
toward non-conformability, the greater dip of the overlying beds would mas” 
probable that the lower dips were of a local character and due to minor NU” 
tions in the Huronian. je 
