LAKES BELTRANfl, TITOMPSON, AND r,T(i FORK 1 2r> 



outlet in the valley in which Beltrami found lake Julia, known as the 

 " Julian sources " of the Mississippi, from which, as he stated, the water 

 drains north to Red lake and south to the Mississippi. There are some 

 evidences of the existence of a larij^e interlohate lake in this retrion a little 

 subsequent to lake Beltrami, whose outlet was westward along the gravelly 

 channel that passes about two miles west of Bagley from Beltrami county 

 into Norman, as represented by Professor Todd, and that may have been 

 the principal way of discharge of lake Beltrami. The connection, how- 

 ever, has not been established. T^ake Beltrami is supposed to have lain 

 mainl}' north of lake Julia, and to have had discharge southward into 

 lake Nicollet. Its elevation was nearly 1.450 feet, or later at about 1,400 

 feet. 



19. Lake Thompson 



There is still another abandoned watercourse lying in the southeastern 

 part of Polk county, running in a southwestward direction, parallel with 

 that in Norman county, which probably drained another glacial lake 

 similar to lake Beltrami but larger, and at a somewhat later stage of the 

 northern ice, when the interlobate area due to the elevation of " Beltrami 

 island " had been largely increased. The size of this lake has not been 

 ascertained, and while it is here named from the Canadian astronomer 

 and geographer who first passed through this valley to the Mississippi,* 

 and its elevation can be given approximately as 1,200 feet, its outlines as 

 shown on the map are hypothetical, being drawn from the contour lines 

 of the maps of Professor Todd and a general knowledge of the manner 

 of retreat of the ice-margin. On the farther retreat of the ice-margin 

 Red lake was the residual inheritor of these waters. From this it seems 

 likely that Beltrami island, lying to the north and northwest of Red lake, 

 cooperated with the margins of the two ice-lobes in separating lake 

 Agassiz into two main parts, one being about 75 feet higher than the 

 other and divided from it by a river about 25 miles in length. This 

 higher lake was responsible for the lacustrine features of the country 

 drained by the Bowstring river. 



20. Lake Big Fork 



This brings us logically to a consideration of Big Fork lake. There is 

 even now sometimes a continuous watercourse between the upper waters 

 of Bowstring river and lake and the Mississippi at Winnibigoshish lake. 

 This connection must have once been quite important and constantly 

 active in turning the upper waters of the Bowstring into the Mississippi. 



* Final Report of the Geological Survey of Minnesota, vol. i, p. 109, note. 



