270 The Aril erica It (ieohxjist. Novcinbor, is95 
turn to tlie soutlieast and to lose its cliariicteristic dip, in a 
large measure, eastward rroiii Pigeon ])oiiit. The line of frac- 
ture and (tf high di]) leaves tiie mainland and passes to l^«le 
Koyale and is lost under the lake at the extremity of that is- 
land. Prof. Irving has suj)posed that it continues, under the 
lake, to Michipicoten island, where it rises to view again, still 
having a southerly dip. It is to be noticed that on each side 
of the lake the line of extreme tilting runs under the lake at 
points nearly opposite each other and near the longitude at 
which they are both deflected toward the southeast. Eastward 
and southeastward from Keweenaw peninsula, and backward 
from its great tilting rampart, lie later sandstones (the '"Eas- 
tern sandstone"), i)ractically concealing, along the lake shore, 
the older geology. Analogy suggests the same age for the 
sandstones that are north of the rampart on the north side of 
the lake. 
But this conclusion does not rest alone on analogy. There 
are certain physical structures that point strongly in the same 
direction. The whole topography of the national boundarj^, 
along the north side of Minnesota, extends, near the coast, as 
far as Thunder bay. But this is farther north than the great 
fracture line which mai'ks the summit of the tilted rampart. 
This summit is characterized by the heavy gabbro masses and 
the red granites and felsytes from twenty to thirty miles 
further south. This hill range (the Mesabi range) leaves the 
north shore of the lake at Pigeon point, some of its great dikes 
being somewhat still further north. It rises again in Isle 
Koyale, but for the most part it is under water entirely east- 
ward from that point. The very southernmost part of this 
line of elevation, i. e., the dikes of the Animikie revolution, 
appears along the north shore of Isle Koyale, where some of its 
characteristic gabbro dikes rise perpendicularly from the water 
to the hightof several hundred feet, sometimes without a shred 
of the Animikie attached. The rocks of the Lucille islands, 
off the coast of Pigeon point, are wholly in the Animikie, con- 
sisting of hardened slates and of great dikes of gabbro that 
run nearly east and west. In the midst of the disturbances 
which they have suffered some of the strata have been fused, 
botli on Pigeon point and amongst these islands, and red gran- 
ite and quartz-porphyry have resulted. Indeed, one or two 
of these islands consist wholly of such red rock. It is proba- 
