206 GEOLOGY OP EASTERN WISCONSIN. 



. point it stretclies away to the southwestward, througli the counties of 

 Manitowoc, Sheboygan, Fond du Lac, Washington, Waukesha, and 

 into the northern portion of Walworth. At this point it divides, one 

 portion extending southward, through the towns of Kichmond and 

 Darien, thence eastward, though not at this point conspicuous, to 

 Lake Geneva, whence the main portion extends northeastward to the 

 vicinity of Burlington, and then southward into Illinois. The other 

 -portion, branching from the main range in the town of Whitewater, 

 about twenty miles north from the state line, extends westward to 

 Kock Kiver, after crossing which, it curves gradually to the north- 

 ward, and enters the district examined by Professor Irving, and will 

 be found described and mapped in his report in this volume. A por- 

 tion of this part is outlined upon the accompanying diagram for the 

 convenience of the reader. 



The peculiar feature of this range that gives rise to its descriptive 

 name, cpnsists of numerous depressions in the drift variously known 

 as " Potash Kettles,'' " Kettles,'' " Potholes," " Pots and Kettles," 

 " Sinks," etc' Those which have most arrested popular attention 

 are circular in outline, and symmetrical in form, not unlike the 

 homely utensils that have given them a name. 



Occasionally they approach the form of a funnel, or of an inverted 

 bell, while the shallow ones are mere saucer-like hollows. But it is 

 important to observe that large numbers of these depressions are not 

 perfectly circular, but rudely oval, oblong or elliptical, or are ex- 

 tended into trough-like, or even winding hollows, with irregular de- 

 partures from all these forms. 



In depth, these depressions vary from the merest indentation of the 

 surface, to bowls sixty feet or more deep, while in the irregular forms 

 the descent is not unfrequently more than one hundred feet. In most 

 of these cases, however, the rim is irregTilar. Symmetrical cavities 

 seldom exceed sixty or sixty-five feet in depth. The slope of the sides 

 varies greatly, but in the deeper ones it very often reaches an angle 

 of 30° or 35° with the horizon; or in other words, is about as steep as 

 the material will lie. In horizontal dimensions, those that are pop- 

 ularly recognized as kettles seldom exceed 500 feet in diameter; but 

 considered with reference to their origin and structural nature, they 

 cannot be limited to this dimension, and it may be difficult to assign 

 definite limits for them. One of the peculiarities of the range is the 

 large number of small lakes without inlet or outlet that dot its course. 

 So true is this, that in field work I soon learned to anticipate the 



' Compare, On tlie Fresh Water Glacial Drift of the Northwestern States, by Charles 

 Whittlesey, Smithsonian Contributions to Knowledge. 1866. 



