RICE COUNTY. 659 



Blue till.] 



over red till which here lies on the St. Peter and constitutes a flat exposure 

 on which the kune runs, at considerable elevation above the rest of its 

 course in sees. 8 and 5. Toward the west this quickly changes to blue till, 

 and toward the east it seems to be overlain by blue till. 



The gray, or blue, till which covers the most of the county, is easily 

 distinguished, in general, from the foregoing. It has uniformly bits of 

 Cretaceous shale, often known as slate, disseminated through it. It has 

 fewer stones and pebbles thsin the red till, and is more impervious to water. 

 Its contained stones are predominatingly granitoid, but sometimes dark 

 with hornblende. Among the boulders, as gathered and piled by the farm- 

 ers by the roadsides, on areas of the blue till, will often be seen masses of 

 foreign, nearly white, limestone. These are generally rounded, and weath- 

 ered from long exposure on the surface so as not to show any glacial mark- 

 ings. This gray till also is covered, in the southeastern and southern 

 portions of the county by a loam, sometimes pebbly, the exact origin and 

 relations of which to the rest of the drift cannot be stated. There are also 

 tracts in the timbered district, north and west of the Cannon river, where 

 this blue till is covered by a thickness of six to ten feet of pebbly loam, 

 though in most of that portion of the county the only covering the blue till 

 has seems to be the soil, formed by a change in the till itself. This yellow- 

 ish loam in the valley of Straight river, between Faribault and the mouth of 

 Fall creek, is enormously developed. It there has exposed sections that 

 measure thirty feet perpendicular, and it is apparently as much thicker in 

 most of section 33, Cannon City. In some places here this clay is without 

 pebbles, and might be compared to the "joint clay", so called, of Rock 

 county.* In nearly all exposures it holds a variety of pebbles, with occa- 

 sional stones, and it seems to pass into the stony till by gradual changes. 

 The blue till lies under the soil, except when the yellowish loam inter- 

 venes, in the southeastern and southern parts of the county, on both sides 

 of the Straight river. The thickness of the gray till has been found at 

 several places to exceed one hundred feet, but as these cases were in the 

 digging of wells and the work ceased because of finding water, it is prob- 

 able that the bottoms of these wells were near the bottom of the blue till, 

 where water is generally obtained. The average thickness of the till for 

 Rice would probably amount to about one hundred feet. In the high prai- 



*See pastes 544 and SSI. 



