686 PAUL MacCLINTOCK 



ii) The material, in at least the upper few feet of the terrace, 

 throughout the length of the valley is uniform in size, shape, and 

 structure. The river having a uniform gradient would handle 

 sediment of uniform size through its whole length. This would 

 result in the coarser material in the eastern part of the high terrace, 

 when cut by these outlet waters, being buried below several feet 

 of finer re- worked material covering the low terrace. 



Hi) Its similarity to the Brule-St. Croix outlet of Lake Duluth 

 is noticeable. This latter is also a broad sandy plain with dunes 

 and blowholes upon its surface.^ 



iv) The low gradient, 1.75 feet per mile, for so large a volume of 

 water, would favor a wide rather than a deep cut. 



Against this mode of origin the following points may be 

 registered: 



i) It would be expected that the upper few feet of the terrace 

 would be re-worked by the running water and the material therefor 

 assorted. But this is, as a rule, not the case, for the pebbles are 

 scattered indiscriminately through the sand. 



ii) Weidman states, in relation to the Brule-St. Croix outlet 

 that ". . . . Aside from cutting down a few drift dams that lay 

 across the outlet, there was not much erosion."^ It is possible, 

 then, that there was not enough cutting by the waters of Lake 

 Jean Nicolet to cut the upper terrace to the level of the lower one. 

 However, the rapidity of cutting, depending upon the volume and 

 the velocity of the river as well as the kind of material cut, may 

 not have been the same in the two cases. So the slight amount of 

 cutting of the Brule-St. Croix outlet would not carry a necessary 

 implication against great cutting in the Wisconsin Valley. 



Hi) The relation of the terraces in the four tributary valleys 

 just east of Mazomanie, previously discussed, is significant but not 

 conclusive. 



From the weight of this evidence, the low terrace appears to be 

 a degradational level cut by waters from the glacial lake. 



c) A third suggestion presents itself which combines the first 

 and second in such a way as to obviate many of the difficulties 



' Moses Strong, Geology of Wisconsin, Vol. Ill (1880), p. 387. 

 * Samuel Weidman, personal communication. 



