108 
glomeratic and not infrequently a quartz— 
to mica-schist in petrographic habit. 
The following are the localities of ac- 
cepted Keewatin: 1. Lake of the Woods 
district. Four ridges corresponding to as 
many upward folds of the Archean contain 
‘in the troughs between them the softer 
mica-schists, chlorite-schists, agglomerates, 
etc., of the Keewatin. [Compare Lawson, 
Geol. and Nat. Hist. Sur. Can. 1885, cc., 
pp. 10-22.] On the Minnesota side of the 
lake there is less opportunity for study ; it 
is probable that not all three intervening de- 
pressions will be found south of the inter- 
national boundary. 2. Along Rainy River 
and in the Rainy Lake region a double 
trough formed by the earlier rocks con- 
tains the Lower Huronian series. While 
the rocks consist largely of voleanics now 
altered to hornblende—and_hornblendic 
schists, there are also fissile glossy schists, 
carrying water- worn pebbles, breccias, gray- 
wackes, ete. The Lower Huronian rock 
exposures ofthe northern Rainy Lake basin 
can be traced in direct continuity into the 
rocks in the Lake of the Woods district 
already noted. [Lawson, Amer. Jour. Sci. 
1887, vol. 133, pp. 477, 478.] In 1894 H. 
V. Winchell and U. S. Grant carefully 
mapped this region and described a belt of 
Keewatin ‘‘ conglomerates, slates, sericitic, 
chloritic and hornblendic schists, agglomer- 
ates, graywackes and more or less altered 
igneous rocks, both acid and basic.’”’ The 
most important belt enters Minnesota be- 
tween Rainy Lake City and the north shore 
of Jackfish Bay. The general direction of 
this belt is W. 15°—20° §., according to the 
map referred to, the greater part of the 
area in view lying within Ontario. Many 
of the gold locations around Rainy Lake lie 
in the Keewatin rock areas. [Prelim. Rep. 
on Rainy L. gold region 23d Ann. Rep. 
Geol. and Nat. Hist. Sur. Minn., 1895, pp. 
36-104.] 3. The most eastern of the suc- 
cessive belts of Keewatin rocks extending 
SCIENCE. 
[N.S. Vou. X. No. 239. 
from Ontario into Minnesota is that in ex- 
posure along the boundary between the 
head of Basswood Lake and Lake Saganaga, 
with Knife Lake as a sort of axis. This 
belt, followed in a W., S. W. direction, be- 
comes effectually covered by glacial drift a 
short distance beyond Vermilion Lake. 
Two or three exposures are reported from 
near the Mississippi River. The rocks are 
conglomerates, sericitic schists, more or less 
altered eruptives and the remarkable segre- 
gations of hematite mined between Tower 
and Ely and occurring in what have thus 
far proved leaner deposits eastward, possi- 
bly into the Kaministiquia district of On- 
tario. Economically this is the most im- 
portant Keewatin area in Minnesota thus 
far explored. 
In the eastern and central portions of the 
State are rocks hitherto not generally re- 
garded as Keewatin: 4. Several areas may be 
grouped: (a) At Thomson, Carlton and 
southwestward lies an extensive mass of 
quartzose clastics in which occur lenses or 
beds of slate regarded by Irving and N. H. 
Winchell as Animiké ; locally they are con- 
glomeratic. (>) Around Barnum and Moose 
Lake lies a series of hornblende-biotite 
schists dipping at a low angle southward; 
the texture is rather fine and the general 
aspect of the rocks fresh and sharply erys- 
talline. (c) West of Sturgeon Lake lies a 
belt of hornblende schists dipping at a high 
angle or standing vertical with interleaved 
granitic, gneissic and quartzose masses. 
These schists are, in places, garnetiferous 
and frequently abound in lenses and string- 
ers of quartz. (d) Still farther southwest- 
ward, on the Kettle River, are exposures 
of mica schists with veins and dikes of 
granite within the schists, while (e) at 
Ann River and westward through Mille 
Lacs, Benton, Sherburne and Stearns coun- 
ties are enormous masses of hornblende- 
biotite granite. These granites in their 
freshest condition carry augite cores within 
