362 COPPER-BEARING ROCKS OF LAKE SUPERIOR. 
reasons from those appealed to by Foster and Whitney. In its quartzose 
character the Eastern Sandstone has, too, something in common with the 
uppermost layers of the sandstone of the western side of Keweenaw Point, 
where a distinct tendency to become more quartzose is to be seen, although 
there is always a considerable difference in this respect between the two 
sandstones. It would also be easy to understand how to the eastward this 
uppermost sandstone might, by overlapping, pass on to the older rocks with 
a small thickness, while constituting to the west only the uppermost layer 
of a great series. 
There are some difficulties, however, in the way of an acceptance of 
this view. The throw of the fault would have to be enormously great— 
at least 35,000 feet—and much greater than is needed for the fault which I 
have supposed to exist along this contact line. Subsequently to the fault- 
ing, or during it, an amount of hard resistant material 35,000 feet in height, 
several miles in width, and over one hundred in length, must have been 
denuded on one side of this fault, while on the other an insignificant 
amount of a fragile sandstone was left standing. A yet more serious 
difficulty is found in the way, already described, in which the Eastern 
Sandstone crosses the course of the beds of the South Range east of Lake 
Agogebic. Were it merely an upper member of a series of which they form 
the bottom portions, the two formations could not possibly sustain any such 
relations as they do. They were very plainly shown by Pumpelly, in his 
description of the place above alluded to, to be in true unconformity to 
one another, and the additional facts obtained by Mr. McKinlay amply 
sustain Pumpelly’s descriptions. 
Pumpelly’s conclusion, after making these observations, was, that the 
junction line between the Eastern Sandstone and the inclined beds of the 
Keweenaw Range was an old shore-cliff, instead of a fault line, against which 
the sandstones were deposited. This conclusion was supposed to be cor- 
roborated by the finding of abundant pebbles of the Keweenawan diabase 
in the Eastern Sandstone near the contact, on the Douglas Houghton River. 
It is not impossible, however, that both he and Agassiz before him? did, as 
Wadsworth says, mistake a bed intercalated with the Keweenaw Series as 
‘Proc. Bost. Soc. Nat. Hist., 1867, XI, p. 244. 
