226 A. P. COLEMAN—CLASTIC HURONIAN ROCKS. 
found to contain 7.44 per cent of carbon, and is porous as though hydro- 
carbons had volatilized leaving round ecayities.* 
These carbonaceous slates may be compared with the black slate of the 
Sudbury region, in which Dr Ellis has found 6.8 per cent of carbon, and 
which was at one time bituminous, as shown in Balfour township by a 
large vein of anthraxolite, once no doubt a fluid or plastic petroleum 
product.t 
The widespread gray wackes need only be mentioned, since they present 
no points of special interest, and the same may be said of the somewhat 
unusual quartzites and grits, but the conglomerates are of more impor- 
tance. They are found in many localities, but only one example will be - 
taken for description, that of Shoal lake, more thoroughly studied than 
the others because occurring close to a number of gold-bearing veins. 
As seen on the shore of the lake, it is a schist-conglomerate consisting 
of green chlorite as a matrix, with well rounded pebbles of all sizes up 
to two feet in diameter embedded in it. That this portion of the con- 
glomerate has undergone shearing is shown by the flattening and even 
tailing out of some of the softer pebbles and the breaking and shifting 
of the parts of some of the harder ones. The commonest rock species in 
the pebbles are quartz-porphyry and porphyrite, felsite, and green schists 
indistinguishable from adjoining Keewatin schists. In addition, there 
are fragments of black and red quartzite and of white, pulverulent sand- 
stone, of vein quartz and of anorthosite. No gneiss or granite has been 
found after careful search, though some quartz-porphyries having the 
crystals of felspar and dihexahedra of quartz much crowded, look, at first 
glance, very like granite. Most of these pebbles are easily matched by 
Keewatin rocks, sometimes, however, many miles distant; a few are 
evidently Couchiching, and none are Laurentian. One rock, a quartz- 
porphyry, half made up of beautiful spherulites having feathery inter- 
growths of quartz and felspar, has not hitherto been recognized in Ontario. 
Two or three miles north of Shoal lake and some distance across the 
strike the rock becomes much less schistose, has a coarse grit as matrix, 
and might almost be described as a breccia, since many of the pebbles 
are scarcely rounded. The pebbles are, however, of the same rock species 
as those on the shore of the lake. 
This band of conglomerate is at least 16 miles long and 2 miles wide. 
Its thickness can hardly be less than a mile and may be almost double 
that, since the dip is steep, but a covering of sand prevents very accurate 
measurements of the width. A very similar conglomerate appears on the 
east shore of Upper Manitou lake, 50 miles to the north, containing por- 
* Geol. Survey of Canada, 1885, pp. 58, 124, and 150, CC. 
+ Ontario Bureau of Mines Report, 1896, p. 159, etcetera. 
