FILLMORE COUNTY. 271 



Topography.] 



stream passes from the St. Lawrence limestone upon the St. Croix sand- 

 stone the same conjunction of circumstances causes another rapid or water- 

 fall. Thus by a series of steps more or less evident, the branches of Root 

 river descend from the area of the Galena limestone to the St. Croix sand- 

 stone. The valleys widen in the sandstone areas, and become abruptly nar- 

 row in the limestone belts. In passing down a stream, within a sandstone 

 area, where the valley is perhaps half a mile wide, with tilled farms in the 

 bottom land, the high bluffs being remote from the stream, the first indica- 

 cation of an approaching change in the formation is the rise of a terrace 

 along the immediate river bank, with an occasional exposure of limerock 

 facing the water. This terrace, which becomes almost continuously rocky, 

 rises slowly till it exposes the full thickness of the rock which causes it. 

 On the other hand the first evidence of a change from limestone to sand- 

 stone, visible in descending the stream, is the occurrence of a waterfall or 

 rapid. Such changes produce water-powers, many of which have been 

 improved. Hence the location of a flouring-mill, on one of these branches, 

 is an intimation to the geologist that at that point one of his boundary lines 

 crosses that stream. Around these points gathered the first village settle- 

 ments. Preston is located where the water-power formed by the descent 

 of the river from the Shakopee to the Jordan induced the construction 

 of mills. The water-power at Chatfield is formed in the same way. Near 

 Fillmore the branches of Root river, known as Deer and Bear creeks, afford 

 good water-powers by their descent from the Trenton to the St. Peter. 

 Mills have been built at both points. On the south branch of Root river, 

 above Forestville, the stream leaves the Trenton, and the waterfall has been 

 improved in the same manner, at Baldwin's mill. The same fact is illus- 

 trated by a great number of eastward flowing streams in the eastern border 

 counties, between Fillmore county and the falls of St. Anthony at Minne- 

 apolis. Of course rapids are also likely to be formed, specially in small 

 streams, when passing through the areas of rocks of uniform hardness. 

 Such water-powers, and others that are formed by the construction of dams, 

 do not fall into this class. 



While the immediate valleys of Root river and its tributaries are apt 

 to be rocky, the country that spreads out in either direction, after leaving 

 the valleys, is not rough. It is rolling, or undulating. In the eastern por- 



