68 Wl Jé% YIM EILNUMOIETE 
to comprise the rocks older than the Algonkian, which are dominantly of 
igneous origin, but which may include subordinate amounts of sediments. 
Recent work in northwestern Europe, and especially in Scotland, Scandi- 
dinavia, and Finland, where the ancient rocks are best exposed in Europe, 
shows that these modifications in the definitions of the Archean and Algon- 
kian are also there applicable. The changes are quite in line with what 
might be expected ; for in recent years no one feature in geological advance 
has been more significant than the sweeping away of sharp dividing lines 
between the various periods. 
Second, the iron-bearing formations of the Vermilion and similar dis- 
tricts I have heretofore regarded as Lower Huronian. In placing these 
formations in the Archean I recognize three series in which productive ore 
formations are found, the Upper Huronian, the Lower Huronian, and the 
Archean. 
The evidence upon which these modifications of my opinion concerning 
Lake Superior stratigraphy are based cannot be here presented in detail. It 
will be fully given in a monograph upon the Vermilion district, to be pub- 
lished later. In general it may, however, be stated that our work in the Ver- 
milion district of Minnesota and on the Canadian side of the international 
boundary has convinced us that bands of sedimentary iron-bearing formations 
are interstratified with the upper. part of the oldest series of the Lake Superior 
region, composed of greenstones, greenstone schist, and tuffs, although the 
thick productive belts of the Archean appear to rest upon the greenstones 
and greenstone schists. 
Professor Van Hise here lends his weighty support to some 
views long held by others. It is admitted that true sediments 
occur in his old Basal Complex, though he does not carry this 
admission to its logical conclusion and attach the sediments to 
his Algonkian. Intrusive into these sediments are the granite 
gneisses of the Complex, a position held by Lawson,* Coleman? 
and others. Among these I now place Van Hise, for the Mona 
and Kitchi schists of Marquette containing banded jasper are 
pierced by the granites of the Basal Complex according to his 
description. 
The succession held by me 1s as follows :4 
1. the Cambrian represented by athe Lake Superior sand- 
stone. 
2. The Keweenawan. 
t Geol. Sur., Can., 1885 and 1887. 3 Mon. U.S. Geol. Sur., XXVIII, p. 186. 
2 Reports Bur. of Mines, Ont. 4Cf. Am. Geol., XXVIII, 1901, p. 19. 
