186 GEOLOGY OF EASTERN WISCONSIN. 



In the lowlands, the Grass and Sedge marshes which correspond to, 

 and in many cases are, unquestionably the forerunners of the prairies, 

 are like them, chiefly confined to the southwestern region. 



As we enter the dense forests to the north, the Tamarac swamps 

 almost entirely replace them, and these in turn, in the still higher 

 latitudes, are in part replaced by the Cedar and Spruce swamps. The 

 Ash swamps are more abundant and extensive at the north, and the 

 Yellow Birch flats are entirely northern. 



The distribution of the Heath, or Cranberry group, is not less in- 

 teresting than important. The marshes occupied by this class readily 

 arrange themselves, on inspection, into four clusters, having a definite 

 relationship to the geological formations. Those in the northwestern 

 part of the district are to be grouped with the great marshes near 

 Berlin and to the -.vestward, and rest upon the Potsdam sandstone. 

 Those in the western part of Jefferson county lie upon, or near, the 

 St. Peters sandstone. Those in Oconomowoc, Concord, Hebron, Sum- 

 mit, Delafield, Ottawa, Eagle, Richmond and Sugar Creek, form a 

 numerous group of small marshes, and rest upon a sandy district that 

 seems to have had its origin in drift from the arenaceous layers of the 

 Cincinnati shale, subsequently modified by lake action, of which the 

 swamps are the lingering representatives. The fourth group com- 

 prises those that lie along the line of the ancient sand beaches of Lake 

 Michigan, of which the marshes near Sturgeon Bay and Peshtigo are 

 examples. The demand for silica is thus shown in the natural dis- 

 tribution of the plant, and we have in this a beautiful illustration of 

 the fundamental principle insisted upon in this report. Native cran- 

 berries occur at the following locations: 



Sugar Creek, T. 3, R. 16 E. Sec. 18. 



Richmond, T. 3, R. 15 E. Sec. 18. 



Eagle, T. 5, R. 17 E. Sec. 31, N. W. qr. 



Ottawa, T. 6, R. 17 E. Sees. 32 and 28. 



Hebron, T. 6, R. 15 E. 



Lake Mills, T. 7, R. 13 E. 



Concord, T. 7, R. 16 E. Sec. 26. 



Summit, T. 7, R, 17 E. Sees. 9 and 12, N. W. qr. 



Delafield, T. 7, R. 18 E. Sec. 34, N. E. qr., and sec. 27, S. E. qr. 



Oconomowoc, T. 8, R. 17 E. Sec. 4. 



Oakland, T. 6, R. 13 E. Sec. 3, S. W. qr., and sec. 17. 



Sturgeon Bay, T. 27, R. 26 E. Sec. 12, W. Lf. 



Caledonia, T. 21, R. 14 E. Sec. 29. 



Peshtigo and Marinette, T. 30, R, 23 E. Sec. 21 and adjoining. 



Aurora, T. 18, R. 13 W., where the marshes occupy several sections east and 



southeast of the village of Auroraville, and are among the most extensive and 



productive in the state. 



