14 Captain Bayfield on the 
ries of various colours and degrees of hardness. Some cf 
the hardest are very beautiful, and susceptible of a very fine 
polish, particularly one from Agate Cove. Thisis amygda~ 
loidal porphyry and is an instance of these rocks passing into 
each other. It is bright red, with simall crystals of glassy 
quartz, and here and there iarge nodules of calcedonic agate, 
quartz and calcspar. 
Porphyry commences first at Gros Cap, the entrance of the 
lake. It is not plentiful along the east coast northwards to 
Michipicoten ; but we traced it to Michipicoten Island, off 
the south side of which it forms a chain of small islets, asso- 
ciated with amygdaloid and other trap rocks, 
Like the other rocks of its class, it is seldom seen along the 
coast, between the point last mentioned and the slate islands; 
but is very plentiful along the southern side of the archipe- 
lago of islands off the mouths of Neepigon and Black Bayse 
It occurs also on the south side of Ile Royale ; and occasion« 
ally all along the coast to the westward, to the river St. 
Louis. We never could discover signs of stratification in any 
of the porphyries. 
‘Trap greenstone is also found along the whole extent as 
signed to the two last mentioned rocks. It is frequently por- 
phyritic, containing small rhombic crystals of brownish red 
felspar. It is also occasionnally basaltic both in veins and in 
masses. 
The columns appear not to be easily separated. They are 
occasionally of five unequal sides, but by far the greater num- 
ber have only four. 
The pitchstone was found in small quantities, and in thin 
Jayers in the interstices of the columns. 
The following rough sketch of a small Island in the mouth 
of Neepegon bay,* taken on the spot, will be explanatory. 
There 
* See fig. 1. 
; 
: 
" 
} 
