POSITION OF THE WESTERN SANDSTONE. 259 
The former of those suppositions is, however, at once forbidden by the 
bedded structure of the crystalline rocks, by their manifest identity with 
the bedded rocks of Keweenaw Point, which are never dikes, and also by 
the abundant occurrence in the sandstone, near its contact with the crystal- 
line rocks, of pebbles worn from these rocks. The second supposition is 
much more plausible. It has against it, however, the nature of the sand- 
stone—which resembles more nearly the Eastern Sandstone of Keweenaw 
Point than the sandstones of the Keweenaw Series—and also the occur- 
rence in it of the pebbles just mentioned. Were these pebbles merely such 
as are apt to occur in the conglomerate bands of the upper Keweenawan 
sandstones, they would not be restricted, as they are, to the immediate con- 
tact of the two formations, but would be regularly distributed through the 
sandstone without any reference to the faulting line. 
But a still greater difficulty to overcome on this theory is one con- 
nected with the general structural features of this part of the Lake Supe- 
rior trough. If this sandstone belongs with the Keweenaw Series at all, 7. ¢., 
belongs with the diabases in contact with it, then it must belong with the 
Upper Division of the series. This must be so, because it is continuous 
with the horizontal sandstones of the Apostle Islands and Bayfield County 
coast, which, if they were to be placed in the Keweenaw Series at all, must 
belong in its Upper Division, because they lie directly across the trough of the 
north Wisconsin synclinal, where only upper Keweenawan sandstones could 
lie. Now, westward from the contacts on the Black and other rivers of Doug- 
las County, the same sandstone continues until, on the Saint Louis River, above 
Fond du Lae, it is found resting on the Huronian slates in such a manner 
as to render certain. its original deposition in that position. Westward 
from the eastern point of the contact in Douglas County, between this sand- 
stone and the south-dipping diabases, the contact line cuts across the Ke- 
weenawan belts until it finally reaches the Huronian slates. It is impossi- 
ble to conceive of a fault by which the upper sandstone could have been 
let down into such a position. There thus seems to be no escape from the 
conclusion that in the Western Sandstone we are dealing with the same 
overlying sandstone that presents itself on the south side of Keweenaw 
Point, and that the Douglas County contact line is one of unconformability 
complicated by faulting. 
