DRIFT PHENOMENA IN WISCONSIN I 35 



level, there is a body of till over which is a bed of stoneless and 

 apparently structureless clay. In a depression just above the clay, 

 with till both to the right and left, is a body of loam which pos- 

 sesses the normal characteristics of loess, both as to constitution 

 and structure. It also contains calcareous concretions, but no 

 shells are found. 





Fig. 3. Section of the moraine southeast of Devil's Lake, as exposed in a rail- 

 way cut (1896). 



Away from the ridges the outer face of the moraine from 

 Kilbourn City to Prairie du Sac is bordered by overwash plains, or 

 morainic aprons, in their normal positions and relations, except 

 that in one locality just west of Barbaoo and south of the river, 

 the moraine edge of the overwash plain is built up even with the 

 crest of the moraine itself. 



The margin of the ice across the quartzite range .—\w tracing the 

 moraine over the greater quartzite range, it is found to possess a 

 unique feature in the form of a narrow but sharply defined ridge 

 of drift, formed at the extreme margin of the ice at the time of 

 its maximum advance. For fully eleven miles, with but one 

 decided break, and two short stretches where its development is 

 not strong, this unique marginal ridge separates the drift-covered 

 country on the one hand, from the driftless area on the other. In 

 its course the ridge lies now on slopes, and now on summits, but 

 in both situations preserves its identify. Where it rests on a plain, 

 or nearl}' plain surface, its width at base varies from six to fifteen 

 rods, and its average height is from twenty to thirty feet. Its 

 crest is narrow, often no more than a single rod. Where it lies 

 on a slope, it is asymmetrical in cross section (see Fig. 4), the 



