i8 The American Gcnlocrist. juiy, 1901. 
Huronian conglomerates ; in (jtliers with the underlying green 
schists. 
Similar relations seem to hold in the original Huronian 
area. Murray's Lower Slate conglomerate is just such a rock 
as that at the Dore. It contains at nearly all points at least a 
few pebbles of chert or jasper derived from some earlier sedi- 
ment. Coleman* mentions such pebbles as being found in the 
so-called basal conglomerate at Thessalon. I have myself 
found very numerous and quite large pebbles (up to six inches 
diameter) of banded jasper, in both the Lower and Upper 
Slate conglomerate, forty miles up the Mississaga. Where the 
contact occurs between the Laurentian gneiss on the north and 
the Lower Slate conglomerate, pebbles of jasper are also foimd, 
but not very abundantlv. On the Mississaga the actual contact 
of the conglomerate and granite-gneiss seems to be an eruptive 
one. Murray's mapt shows a fault along the contact line bv 
which he no doubt thought to explain the later consolidation of 
the granite-gneiss. His only printed statement is as follows :% 
*'The northern shore of the lake, and the mountains north from 
it, appear to be composed of granite and syenite ; in both of 
w'hich there is occasionally observable an obscure gneissoid 
structure, giving them the aspect of gneisses, so that here as in 
the vallev of the Spanish river (page i) it is very difficult to. 
say whether they are intrusive or altered rocks." 
Again, in describing a contact twelve miles east of Thessa- 
lon, Murray writes :§ "At the southeast end of lake Pakowa- 
gaming (]\Iud lake) there are red quartzytes, slates, and other 
rocks of the Huronian age, whose place in the series is yet 
uncertain, but they are all twisted, highly tilted north- 
ward or vertical, and on the southwest side of the lake for 
two miles up in the bights of the bays and in positions behind 
the greenstone points and promontories, there are exposures of 
w^ell characterized massive gneiss '^ * * [This] makes it 
very probable that we have here an exhibition of a portion of 
the Laurentian series, brought up against the Huronian from 
a great depth." On the accompanyng atlas a fault line is 
shown for twenty-five miles where the formations come to- 
gether. ]\Iy own observations last summer on lake Pakowa- 
*Bur. of Mines, Ontario, viii, p. 162. 
\Geol. of Can., 1863, Atlas. 
XGeoI. of Can.. 1863, p. 842. 
§Rep. Geol. Sur. Can., 1858, p. 9.~>. 
