Tlie KeweeyiawMi in Minnesota.- — El ft man. 99 
DISTRIBUTION OF BOULDERS. 
Boulders are very abundant in the drift of this region. 
Locally nine-tenths of the drift is made up of boulders from 
four inches to ten or fifteen feet in diameter. The boulders 
found in this region may be referred to two sources: ist, the 
east; and, 2nd, the north and northeast. Those derived from 
the former source are composed entirely of rocks found near 
lake Superior, and consist of felsytes, quartz-porphyries, 
amygdaloidal diabases, Beaver Bay diabase, anorthosyte, and 
sandstones; those from the latter source consist of granites, 
schists, jasper, hematite, magnetite, slates and gabbros, rocks 
known to occur in place north of the present position of the 
boulders. 
The areal limits of the boulders from these two sources are 
easily recognizable. The Highland moraine is composed en- 
tirely of material derived from the east. The Itasca moraine 
consists of northern drift. The Itasca-Highland moraine is 
composed of material derived both from the east and the 
north. The derivation of the drift included in this moraine, 
from two sources; was previously mentioned on the Poplar 
river* and around lake Harriet in T. 60 N., R. 6 W.f The 
Mesabi and Vermilion moraines are derived entirely from the 
north and northeast. In the triangle between the Highland 
and Itasca moraines the glacial drift is composed of alternat- 
ing layers of northern and eastern drift. 
While the northern limit of the southern and eastern drift 
is largely determined by the Itasca moraine, still the eastern 
drift has been observed at Biwabik and Birch lake on the 
Mesabi range; at lake Isabelle T. 62 N., R. 8 W. and on the 
Temperance river in T. 62 N., R. 4 W. The material at the 
last named places is scarce, and the fragments small in size, 
the largest being about two inches in diameter. As this drift 
occurs at a lower altitude and lies in the valleys of rivers 
whose sources are in the area covered by the eastern drift, 
some of it owes its present location to river transportation. 
*N. H. Winchell. Tenth Ann. Report Geol. and Nat. Hist. Sur. of 
Minn., 1881, p. 105. 
fH. V. Winchell. Seventeenth Ann. Report Geol. and Nat. Hist. 
Sur. of Minn., 1888, p. loi. 
