RICE COUNTY. 6(53 



River terraces.] 



by a line of abrupt drift bluffs that rise at once about 60 feet. It is here plainly underlain by the 

 Lower Trenton limestone, six to ten feet above the river, but toward the south it slowly ascends 

 and exhibits its gravelly composition. At Mud creek, which enters the river from the west in 

 sec. 21, the same plain occupies a broad sweep up that valley, and is about 25 feet above 

 the Straight river. The underlying Trenton and green shales, which at first make this terrace 

 very wet, sustaining a copious flow of water in Mud creek, are covered with only a few feet of 

 gravel and soil. Sometimes also the gray till is found to extend under the gravel of the terrace. 

 At Medford the immediate drift bluffs are from fifty to seventy-five feet higher than the terrace, 

 and the terrace is thirty feet above the river. On the east side of the river the terrace extends 

 from Medford at least to the county line northward, and probably about a mile into llice county. 

 The connection which is presumed to exist between this gravel-terrace and the gravel seen in sec- 

 tions 23, 14 and 1 1 , Walcott, where the old outlet of the Straight river begins, has not been traced. 

 The outlet itself, now, in section 14, probably somewhat silted up, is about 1150 feet above the 

 sea, the old river banks rising abruptly on either side about fifty feet, and the country farther 

 back from twenty-five to fifty feet more. The bluffs are continuous from the west-drained marsh 

 to the east-drained, the actual divide being imperceptible and in the marsh in sec. 23, which is 

 drained in both directions. The narrowest place in the marsh is where the road crosses, between 

 sections 13 and 14, and it is here about a third of a mile across, the flow of water here being 

 toward the east. There is a rough and rolling high, timbered, surface toward the west and north, 

 but smooth and treeless toward the east and south. There is a general low tract through sections 

 10 and 11. Wells are shallow and enter gravel and quicksand. The low knolls have a remarkable 

 amount of northern limestone. 



There is a lower terrace, abutting on the St. Peter sandstone, running from Faribault south 

 along the west side of Straight river. This terrace consists of yellow, pebbly clay, sometimes 

 containing boulders, and rises from 25 to 30 feet above the Faribault plain when it first com- 

 mences, but seems to rather fade and mingle, upwardly, with the Trenton flat above, over which 

 is also spread a yellow, pebbly clay. This appears in ascending the river. This terrace is also 

 visible in the Cannon valley, where the two streams combine, and its outline is visible in the val- 

 ley of the creek that joins the Cannon near the fair-ground. Its line of strike passes through the 

 Maple-Lawn cemetery, while the Catholic cemetery is higher, and on the undulating ascent over 

 the St. Peter sandstone. 



Cannon river terraces. As already noted, the Cannon valley is a remark- 

 able one. Some of its remarkable features are exhibited in Rice county, 

 and some of them only in Dakota county. It once conveyed the waters of 

 the Minnesota river across Rice and Dakota counties to the Mississippi 

 valley.* The lake that at first was formed by the damming up of the 

 Minnesota by the ice of the glacial epoch has been described by Mr. Upham 

 in the report on Faribault county. At a certain time during the period of 

 its existence that lake had its discharge through the Cannon valley. Those 

 waters must have entered the county, judging from the hight of the upper 

 terrace-flat, at an elevation of about 1075 feet above the ocean. As the ice 

 withdrew the lake was lowered by finding lower and lower avenues of dis- 

 charge, some of which will be described in the report on Dakota county, 

 till by the retreat of the ice-margin from the valley entirely, it was wholly 

 drained, and the river assumed its present course to the Mississippi. 



*8cc page 461, foot-note ; also page 642. 



