70 Alo S56) [GUAM EIENTMOTOTE, 
narrow band of limestone. These were practically alike in 
every particular and Murray found himself unable to distinguish 
them where the limestone was lacking.t. The Upper Conglom- 
erate carries occasional pebbles of the limestone when near it, 
but usually none are to be found. The limestone band as 
shown in Murray’s map is largely conjectural, the outcrops 
being very few. It seems probable that the break between the 
two conglomerates is not of great significance and that it would 
be well not to attempt a separation of them. 
Many geologists have argued for a division of the Huronian, 
though they have not agreed on the horizon. Alexander Win- 
chell? places the break at the top of the Lower Slate Conglom- 
erate. Pumpelly and Van Hise3 place it above the limestone band. 
The important break must, however, lie much lower. Pebbles 
of banded jasper and hematite occur in the Lower Slate Con- 
glomerate, in great abundance in places, and must have been 
derived from some lower sediment. Logan’s white quartzite 
often becomes a conglomerate and is evidently only a phase of 
the Lower Slate Conglomerate. Excepting the chloritic slates 
we have, accordingly, in all the lower part of the Mississaga 
Huronian area evidence of the existence of a lower sediment. 
The probable occurrence of this banded jasper was recognized 
by Logan himself, though outcrops were not discovered. This 
lower conglomerate with jasper and chert pebbles thus becomes 
of the greatest value in working out Lake Superior stratigraphy, 
a fact emphasized by Coleman in a paper on the subject.‘ 
Logan also recognized its value, and correlated slate conglomer- 
ates in the Temiscaming, Sudbury, Mississaga, Batchawana, and 
Michipicoten districts. In describing the Doré series in the last 
be) 
district he mentions’ pebbles of a “‘chert-like stone,’ and near 
Batchawana Bay jasper conglomerate was found. In maps of 
both these regions there were included within the Huronian, 
rocks which are now recognized as the source of the jasper and 
t Rep. Geol. Sur., 1858, p. 94. 
2 Bull. Geol. Soc. Am., 11, 1891. 4 Rep. Bur. of Mines, Ont., 1900, pp. 182-86. 
3 Am. Jour. Sct., III, 1892, p. 42. 5 Geol. Can., 1863, p. 54. 
