ArcJican of Miiuicsota ami lu/i/aiid. — ]\i'/iclicl/. 225 
To recapitulate briefly, the descending order of the parts 
of the Aichean seems to be as follows: 
1. Granitic protrusion and extended metamorphism of the 
elastics. 
2. Upper Keewatin. When not metamorphosed these are 
conglomerates, graywackcs and clay slates, sometimes min- 
gled with greenish debris. 
3. Granitic intrusion, the intrusive rock being usually 
fine-grained, but also constituting coarse granite. 
4. Lower Keewatin or Kawishiwin, mainly greenstones, 
both massive and fragmental. 
From this it appears that some order is beginning to ap- 
pear in that ancient group of rocks which for many years geo- 
logists have been content to designate simply as Archean or 
as the fundamental complex. 
For a knowledge of the results obtained by similar studies 
in Finland we are indebted to the Guide-book of the Inter- 
national Congress of Geologists of the seventh session, in 
which the government geologist, J. J. Sederholm, gives a suc- 
cinct description.* .\ condensed statement of the structure 
and stratification of the Finland Archean, as given by Seder- 
holm, is as follows 'if 
In descending order: 
1. Post-Bothnian granite. 
2. Bothnian schists. 
3. Pre-Bothnian terrane of gneiss. 
At the bottom of the known Archean (No. 3 pre-Both- 
]iian gneiss) there is therefore, as further described by Seder- 
holm, a series essentially gneissic but containing mica schists, 
and porphyroids. These schists and porphyroids, on the as- 
sumption that they are metamorphic fragmentals, iniplv the 
existence of some older rocks from which the debris was de- 
rived. What the nature of that older nick mav have been is 
not stated definitely by Sederholrn, but it is possible to infer 
from inclusions whicli he mentions in the granites that pierce 
these schists that it was a basic rock. Such inclusions are 
*Reference may be made to a letter from Dr. Bascom in the Ameri- 
can Geologist, Nov. 1897, p. 33g, in which is dcsrribed the excursion to 
Finland, with notes on the geology. 
tA translation of Sederholm's description of liusi- formations is given 
in tliis nunil)cr of the American Geolocmst. 
