146 SA LI SB URY A ND A TWO OD 



height, and the height of the lake when at its maximum, are not 

 known. But at a point three miles southeast of Ablemans on the 

 surface of a sandstone slope, water-worn gravel occurs, the peb- 

 bles of which were derived from the local rock. On the slope 

 below the gravel, the surface is covered with loam which has a 

 suggestion of stratification, while above it, the soil and subsoil 

 appear to be the product of local rock decomposition. This 

 water-worn gravel of local origin on a steep slope facing the 

 valley, probably represents the work of the waves of this lake, 

 perhaps when it stood at its maximum height. This gravel is 

 about 125 feet, according to aneroid measurement, above the 

 Baraboo River. 



This lake did not entirely disappear when the ice retreated, 

 for the drift which the ice left, especially the terminal moraine, 

 still obstructed drainage to the east. The moraine, however, 

 was not so high as the former outlet of the lake had been, so 

 that as the ice retreated, the water flowed over the moraine to 

 the east, and drew down the level of the lake. The postglacial 

 valley cut through the moraine is about ninety feet deep. 



Besides being obstructed where crossed by the terminal 

 sTi'oraine, the valley of the Baraboo was clogged to a lesser extent 

 ,by deep deposits between the moraine and the Lower Narrows. 

 At one or two places near the city of Baraboo, such obstructions, 

 now removed, appear to have existed. Just above the "Lower 

 JSIarrows" there is positive evidence that the valley was choked 

 with drift. Here in subsequent time, the river has cut through 

 the drift-filling of the preglacial valley, developing a passage 

 about twenty rods wide and thirty-five deep. If this\ passage 

 were filled with drift, reproducing the surface left by the ice, 

 the broad valley above it would be flooded, producing a lake. 

 At the outset, this lake must have been considerably lower than 

 the one above the moraine to the west, but drainage from the 

 latter into the former soon lowered the barrier between them, 

 bringing the upper lake to the level of the lower. The lake 

 below Baraboo was much less extensive than the one above, and 

 probably shorter lived. It became extinct by the cutting of its 



