16 Y^^ISCONSIiS" ACADEMY SCIENCES, ARTS, AND LETTERS. 



purer kaolin is found immediately below the sandstone, next be- 

 low a partially kaolinized rock, and next below again the entirely 

 unaltered rock. Such sections are common in the district. 



The kaolin localities appear to be almost entirely within the drift- 

 less area, or at least where the drift is very thin and the glacial 

 action has been insignificant. This fact becomes a significant one, 

 when we consider that over all the great Archaean region of the 

 north half of the state, which is drift covered, no occurrence of 

 kaolin is known; all the known occurrences being confined to that 

 comparatively small district where the Archaean rocks are found 

 within the driftless area. I am inclined to attribute this absence 

 of kaolinized rock in the northern portion of the state to the de- 

 nuding agency of the drift forces, following Dr. T. S. Hunt, who 

 has made the same suggestion* in explanation of the non-disinte- 

 grated condition of the gneissic rocks of the Blue Kidge in the 

 northern Atlantic States, the same rocks further south being con- 

 stantly found decomposed to considerable depths. 



Where and Jtoiv to searcJi for kaolin in Wisconsin. — If it be a fact that 

 the drift forces have removed all kaolinized rock they have encoun- 

 tered, then at once we ma}^ conclude that search at any considera- 

 ble distance north of the drift limit is not likely to be rewarded 

 with success. An exception to this might be wdiere the kaolin has 

 been formed underneath protecting masses of sandstone. Within the 

 thus restricted district, moreover, the labor of the search may be much 

 lessened by the recognition of a few simple guiding facts. The ex- 

 plorer should visit the known outcrops of kaolin, note the rock 

 from which it has decomposed, measure carefully its strike and 

 then follow the line thus obtained until other patches are found. 

 Having once noted the kind of rock tending to produce the kaolin, 

 (in this region usually a pinkish felspathic gneiss or granite,) by 

 following the strike of any similar bed kaolin will probably sooner 

 or later be found. The search would be best made with a boring- 

 tool of some simple kind. Should sandstone be struck in the bor- 

 ing the kaolin may yet underlie it. The explorer should at 

 the outset divest himself of the idea that the kaolin occurs in a 

 continuous horizontal bed. 



Kaolin on the Wisconsin River. — The best known kaolin deposits 

 in Wisconsin are those that occur on and near the Wisconsin Riv- 



"■^Loc. cit. 



