QUARTZ-PORPHYRIES OF THE NORTH SHORE. 149 
evident that in them, too, we have to do merely with interbedded porphyry 
masses. 
As to the more minute characters of these other porphyries of the North 
Shore we may say that granitic porphyries are not common; that where 
they occur, except when almost granite in texture, they can generally be 
carried directly into true quartz-porphyries, often showing the fine contorted 
banding of the Palisade rock; and that a very common feature of the quartz- 
porphyries and felsites is a close, angular jointing, which, on a weathered 
surface, is often developed to such a degree that it is impossible to obtain a 
hand specimen of any size, or to get a fresh fracture, a slight blow of the 
hammer against the cliff bringing down showers of small angular fragments. 
Where the fine banding mentioned is developed it is frequently possible to 
trace the rock with contorted banding into massive and wholly unbanded 
kinds with very large porphyritic quartzes and orthoclases. This change is 
to be seen beautifully at several points on the Canada shore between Black 
Bay and Saint Ignace, notably at Bead Island, opposite Lamb Island light- 
house, at the mouth of Nipigon Straits. At one point on the North Shore, 
between Beaver Bay and the Palisades, was noticed a pinkish quartzose 
porphyry, in which the lighter matrix is filled with a darker porphyry, ar- 
ranged in all sorts of fantastic and snake-like forms, single figures ex- 
tending sometimes for several feet with a width of two or three inches, and 
running from these dimensions down to mere lines, the whole presenting 
the appearance of a somewhat irregularly figured carpet. This peculiar 
structure I attribute to flowing in a viscous condition. At several places, as 
for instance on the Devil’s Track River, near the lake shore, and again on 
the shore of the Pigeon River Indian reservation, the porphyry was no- 
ticed with a tendency to come out in thin, flat pieces, or pieces with a 
corrugated surface, but in this case, as usual, it runs into the compact struct- 
ureless kind. 
Quartziferous porphyries are again largely developed on the South 
Shore, with the same structural features as noted on the North Shore. Mount 
Houghton and the Bare Hills of the eastern end of Keweenaw Point are 
portions of a belt of banded quartziferous porphyry. These were long since 
mentioned by Foster and Whitney, who describe the rock as hardened 
