72 A, B. WILLMOTT 
these earliest sediments. Because of the impossibility of sepa- 
rating the sediment from the inclosing greenstones and green 
schists except on very large scale maps, both will usually be 
mapped together. This must also be the case for many years 
over vast areas of Canada until the regions become more acces- 
sible. For this reason I doubt the advisability of attempting 
the separation of the volcanics and sediments except in limited 
areas of economic value. Here each would be given forma- 
tional names, just as Van Hise has done with the Ely greenstone 
and the Soudan iron formation. In other places the volcanics 
and eruptives will take the name of the sediment with which 
they are associated. The lowest sedimentary series of the Lake 
Superior region is the Lower Huronian. These sediments were 
included in the areas mapped as Huronian by Logan in 1863, 
and, although not actually found in place by him, were recog- 
nized from their fragments, and to him should be given the 
credit. These rocks have always been mapped as Huronian by 
the Canadian Survey. 
For these reasons, Lower Huronian is to be preferred to 
Archean in describing these rocks. Failing Lower Huronian, 
Keewatin should be adopted, for it too has priority over Archean 
as used in this connection. 
If Lower Huronian is to be substituted for Archean it fol- 
lows that Upper Huronian would properly replace Van Hise’s 
Lower Huronian. Van Hise correlates (p. 411) the Ogishke 
conglomerate with the Doré conglomerate, and Logan con- 
sidered this the equivalent of his Lower Slate Conglomerate. 
N. H. Winchell* and Alexander Winchell? both correlate the 
Ogishke conglomerate with Logan’s slate conglomerate. With 
these correlations I agree on lithological grounds and because 
of the sequence all around the lake. This may possibly be 
proved, or at least supported in another way. Coleman has 
shown, in a paper already referred to,3 the wide distribution of 
the slate conglomerates, and that all carry jasper or equivalent 
* Sixteenth Ann. Rep. Minn. Geol. Sur., 1887, pp. 12-40. 
2 [bid., pp. 145-71. 3 Rep. Bur. of Mines, Ont., 1900. 
