466 RED CLAY AND DRIFT OF OCONTO AND WOLF RIVERS. 

 At Grand Chute, on the Fox River — 



Feet. 



1. Red clay, ....... 30 



2. Coarse sand and gravel drift, ..... 20 



3. Limestone, Silurian. 



Three miles below the Falls of Wolf River, the coarse sandy drift of the falls 

 begins to show red clay, sometimes mingled in confusion, and at others in alternate 

 beds, containing granitic pebbles, as well as those of limestone. This fact, and 

 others that fell under my notice, indicate a current from the south and southwest 

 during a portion of the diluvial epoch. Descending Wolf River to Oshkosh, the 

 red clay was found to occupy its valley, with beds of coarse yellow sand, or of 

 gravel, on its surface, or interbedded near its surface. These variations in the 

 composition of the drift are probably owing to changes in the intensity, direction, 

 and force of the diluvial currents. 



About the heads of the west fork of the Oconto, are long, mountain-like ridges of 

 sandy drift, rising one hundred and fifty and two hundred and fifty feet above the 

 streams, destitute of water, and covered with heavy birch timber. On these up- 

 lands are immense blocks of red syenitic granite, with a large proportion of felspar ; 

 their diameters ranging from five to twenty feet. There are large tracts of these 

 drift-beds covered with sink-holes of irregular forms, but inclined to be circular, 

 from ten to one hundred feet deep, with steep sides, and without water. They 

 look like a field of mounds or 11 moraines" inverted, the ridges sharp-cut and very 

 thin ; a mere ridge between one and its next neighbour. The boulders are more 

 numerous on the narrow spaces between these cavities than they are in them, and 

 the timber grows in as well as out of them. The side view, at a little distance, 

 resembles the form of a highly agitated sea suddenly made immovable and solid. 

 They are not the results of currents of water and eddies, depositing sediment in 

 basins. The sides are too steep, the form being conical or funnel-shaped, and 

 the ridges between them incapable of resisting even a moderately flowing current 

 of water. The thought that took possession of my mind on the spot was, that a 

 mixed mass of ice and drift had been placed there, the former thawing out after 

 deposition, and after the retiring of the waters. Dr. Beach found similar appear- 

 ances on the head waters of the eastern fork. 



