424 The American Geologist. June, isos 
highest level of the glacial lake Agassiz, which during the departure of 
the ice-sheet was pout np in the basin of the Red river of the North and 
of lake Winnipeg by the receding ice-barrier.* The hight of Red lake 
above the sea is ascertained to be 1172 feet; and of the Lake of the 
Woods, in its stages of low and high water, 1057 to 1063 feet. North- 
east of Red lake the Tamarack river drains a large tract of tamarack, 
spruce, and arbor vitte swamp, which reaches to the divide between the 
Tamarack river and the West branch of the Bowstring river (more com- 
monly called the Big Fork), tributary to Rainy river, the hight of the 
divide being only 15 to 30 feet above Red lake. Similar low swamp land 
forms nearly the whole northern and northwestern shore of Red lake 
and is crossed by this railroad survey continuously along its first eight- 
een miles beyond Red lake; but at a distance of twenty-nine miles from 
the lake the profile shows an ascent crossing the highest beach of lake 
Agassiz, which there is 1215 feet above the sea. The next seventeen 
miles of the profile extend across the northeastern edge of a large island 
of lake Agassiz, rising on that line to a maximum hight of 1283 feet, 
with a moderately undulating drift-covered surface. In the next fifteen 
miles, which comprise the descent on a similar but smoother drift sur- 
face from the highest shore of lake Agassiz to the War Road river, an 
afflucMit of the Lake of the Woods, the profile crosses a succession of ten 
lower beaches of lake Agassiz, marking stages in the gradual uplifting 
of the land and subsidence of the lake, their altitudes above the sea be- 
ing 1196, 1173, 1156, 1143, 1127, 1116, 1106, 1099, 1093, and 1087 feet. 
These data show that lake Agassiz in its highest stage had a large 
island northwest of Red lake, comprising the headwaters of numerous 
streams flowing outward from it to the Lake of the Woods, Rainy river, 
Red lake, the Red Lake river, and the Red river of the North. This 
island had probably a diameter of forty miles or more, with an area ex- 
■ceeding 1000 square miles, of which apparently more than half is in 
Beltrami county, the portion farther west being chiefly in Marshall 
county, Minn. For this tract, which has before been supposed to be 
comparatively low and perhaps wholly beneath the highest level of lake 
Agassiz, the name Beltrami Island is proposed, in recognition of the ex- 
ploration of the region of Red lake and the Julian or most northern 
sources of the Mississippi by Beltrami in 1823 (Geol. of Minn., vol. i, 
1884, pp. 44-50, with map). As Prof. N. H. Winchell wrote in the histor- 
ical sketch here cited, this district "is still nearly as wild and uninhab- 
ited as when Mr. Beltrami passed through it." During the field work of 
this survey the present season, the boundaries and contour of this island 
will be mapped. 
Beltrami island lies in the course of northwestward and northward 
continuation of the Mesabi or eleventh moraine of the series mapped in 
*Geol. and Nat. Hist. Survey of Minn., Eighth annual report, for 1879, 
pp. 84-90; Eleventh annual report, for 1882, pp. 137-153, with map; Final 
report, vol. ii, 1888, pp. 517-527. U. S. Geol. Survey, Bulletin No. 39, 
with map, 1887. Geol. and Nat. Hist. Survey of Canada, Annual report, 
new series, vol, iv, for 1888-89, part E, with maps and sections. Am. 
■Geologist, vol. vii, pp. 188-194, 222-231, March and April, 1891. 
