THE GLACIAL DRIFT. 609 



Plate XXVI shows the boundary of the driftless region for the lar- 

 ger part of its extent in Wisconsin. This line lies chiefly in the Cen- 

 tral Wisconsin district, but for the four townships south of Dane 

 county has been copied from the maps of Mr. Strong. Entering 

 Dane county on the middle of the south line of Montrosej T. 5, R. 8 

 E., it nearly coincides with Sugar river as far as the head of that 

 stream in Cross Plains, T. 7, R. 7 E. Along this portion of its 

 course the heaviest drift deposits are several miles to the eastward of 

 the boundary, which they gradually near to the northward. From 

 the head of Sugar river the divide is crossed to Black Earth river, the 

 northern side of which is followed into the towns of Black Earth and 

 Mazomanie, T. 8, R. 6 E. Thence, bending northward, and cross- 

 ing the Wisconsin between Sank City and the mouth of Honey creek, 

 the line pursues a northerly course across Sauk Prairie to the foot of 

 the Baraboo quartzite ranges, morainic drift occurring from half a 

 mile to two or three miles east of it. On top of the quartzite ranges 

 no drift is seen west of Devil's Lake, in whose valley are, however, 

 heavy deposits, and the line appears thus to make a slight bend east- 

 ward. North of the ridge, however, it is further west again, for large 

 heaps occur at Baraboo, and bowlders are to be seen two or three 

 miles west of that place. 



Beyond the Baraboo, the line continues in a northerly direction to 

 the north line of Sauk county, where it bends out to the westward 

 along the high ground that forms the rim of the sand plain of Juneau 

 and Adams counties, for granitic and other bowlders may be seen 

 all along the road from Kilbourn to Mauston, as far as the N". W. qr. 

 of Sec. 27, T. 14, E,. 5 E. Very soon, however, a sharp bend is made 

 to the eastward again, the line following the inner edge of the high 

 ground to the Wisconsin, above the Dalles, and, after crossing the 

 river, in a curving direction through southeastern Adams county. 

 Turnino- then northward, it lies a short distance west of the east line 



O ' 



of that county, until its northern portion is reached, when, curving 

 once more to the westward, it crosses the Wisconsin again near 

 Grand Rapids, in Wood county. A sketch map of the Wisconsin 

 driftless area, given by J. D. Whitney, 1 includes all of Adams and 

 the eastern part of Juneau counties within the drift-bearing area, 

 and shows the limit altogether to the west of the Wisconsin. This 

 portion of the state he does not, however, seem to have mapped from 

 personal investigation. I have never seen any sign of glacial drift in 

 the district specified, and, indeed, the numerous fragile sandstone 

 peaks occurring within it preclude the idea that the glacial forces 



1 Geological Survej of Wisconsin, Vol. I. Albany, 1862. 

 Wis. SUB. 39 



