FILLMORE COUNTY. 311 



Drift.] 



needle. Limonite iron ore is regarded usually as non-magnetic. In large 

 quantities, near the surface, it seems to influence the magnetic currents. 

 What relation this ore bears to the Cretaceous is not known, except that it 

 has been found to overlie the Cambrian rocks, or to cover their surfaces 

 with a scale, where the Cretaceous overlies them unconformably. 



The Drift. The drift presents some interesting features in Fillmore 

 county. The western limit of that well-known tract denominated the 

 driftless area, 'by Prof. J. D. Whitney, crosses this county. This boundary 

 is not well-defined. There is a very conspicuous absence of the bluish clay 

 and the northern boulders that distinguish the true northern drift-sheet of 

 counties further west and north, throughout the eastern two-thirds of the 

 county, the boundary line running, approximately, from the southeast cor- 

 ner of Bristol township, to the northeast corner of Jordan. West of that 

 line, which is modified in its course by valleys and uplands, is a belt of five 

 or six miles in width which is characterized by an overlapping of the loess 



loam on the thinning out edge of the drift-sheet. This belt is character- 







ized further by peculiar local modifications of the materials of the drift, 

 due to the underlying rock, as mentioned under the head of Cretaceous. 

 West of this belt the true drift becomes prevalent, consisting of clay with 

 many boulders. 



That tract which is regarded as driftless* is, so far as Fillmore county 

 is concerned, not without some evidences of having been subjected, at some 

 time, to a force similar to that which is supposed to have deposited the 

 great drift-sheet of the Northwest. There are isolated patches of gravel, 

 with small stones, sometimes cemented into a crag, which have been noted 

 in Fillmore county, scattered sparingly over the eastern part of the county, 

 as the following field minutes will show: 



Drift pebbles are in the street north of the school house, S. W. J sec. 25, Amherst. 



Drift occurs in the form of gravel and boulders, some of them a foot in diameter, S. W. J 

 sec. 4, Fountain, on the east bank of Sugar creek, in the road ; seen in going east from the quarry 

 of Enoch Winslow. At Fountain village there is said to be no drift between the loess loam and 

 the rock. 



A little drift may be seen at the Tunnel oiills, see. 34, Sumner. 



There is a little fine drift visible along the road, S. E. J sec. 25, Sumner. 



At Chat field there is some gravelly drift with small boulders, visible in the street near the 

 mill-race. 



Drift, with pebbles and stones, appears about a mile south of Clear Grit, on the Shakopee 

 terrace along the highway ; also on the road to Carimona, near Preston. 



*J D. Whitney, Geology of Wisconsin, Vol. I, pages 114, 139. 



