NOURNAL OF GEOLOGY 
JULY-AUGOST, 1809 
MoE VW ANAL CITE ROCK FROM. LAKE SUPERTOR 
Amonc other regions on the northern shores of Lake Superior 
examined last summer by the writer for the Ontario Bureau of 
Mines the vicinity of Heron Bay, where the Canadian Pacific 
Railway first touches the lake when coming from the east, proved 
very interesting, a thick series of schist conglomerates with peb- 
bles and bowlders mainly of felsite and quartz-porphyry occur- 
ring there, mapped by Dr. Bell of the Canadian Geological 
Survey as Huronian. Along the rocky shore of the bay, and 
also in cuttings on the railway west of the station, good expo- 
sures of these rocks are seen, sometimes so rolled out that the 
forms of the pebbles are almost, or completely, lost. Crossing 
the schist conglomerates are numerous dikes, which unfortunately 
were not carefully studied owing to lack of time, though hand 
specimens of the more typical dike rocks were taken. In the 
field the dikes were considered to consist of diabase, diabase- 
porphyrite, and felsite, all common rocks in the western 
Keewatin. 
Microscopical study of the specimens obtained showed that 
the diabase and porphyrite present no unusual features, and that 
one of the felsitic-looking rocks is quartzless porphyry of a kind 
common in western Ontario. Another rock taken for felsite, 
dark red and slightly spotted with green, turns out, however, to 
Vol. VII, No. 5. 431 
