640 THE GEOLOGY OF MINNESOTA. 



[Claci.il drift. Terminal moraines, 



casional layers of stratified gravel and sand, commonly only a few inches 

 or at most a few feet thick. From these veins or beds of modified drift, 

 wells often obtain a large supply of water under such pressure that it rises 



considerably above the stratum in which it is found. 



The only well in this county that has gone deep enough to strike the bed-rock beneath the 

 drift east of the Minnesota valley is at Montgomery, and was bored to supply water for Miller & 

 Phelps' flour mill. Its depth is 246 feet, the section being till, yellow near the surface and dark 

 blue below, 186 feet, containing a layer one and a half feet thick of blue sand at the depth of 130 

 feet; then sand, mostly soft, but hard in occasional layers six to twelve inches thick, 55 feet, to 

 white sandstone, probably the Saint Peter formation, into which the well was bored only 5 feet. 

 Water, coming plentifully from this porous sandstone, rose 130 feet. No fossils were observed. 



A bed of cemented gravel and sand, made a hard conglomerate rock by the deposition of 

 carbonate of lime and magnesia from infiltrating water, occurs in the modified drift about a half 

 mile east of Le Sueur, being in the east side of a ravine near the center of section 36, where the 

 Le Sueur prairie descends to the second terrace. The thickness of this stratum is about 10 feet. 

 It has been quarried by John Bachmann to supply the stone for waling his cellar. 



About one and a half miles farther east, probably in the N. E. } of section 31, Tyrone, the 

 road along the south side of the Little Le Sueur creek, in ascending to the surface of the general 

 drift-sheet, has made several cuts in till, which is weathered to a yellowish color, and here con- 

 tains thin, light-gray, calcareous veins or seams, apparently concretionary in their origin, varying 

 from an eighth to a half of an inch in thickness, and extending at least three or four feet, interlock- 

 ing with each other in crookedly vertical, oblique and horizontal directions. The only observation 

 similar to this, which I can refer to, was near Mankato Junction, and is described and figured on 

 page 442. Finely pulverized magnesian limestone is a considerable ingredient in the drift of all 

 southern and western Minnesota. 



Terminal moraines. In the description of the surface features of this 

 county, the contour of the terminal moraines which cover its east edge 

 and cross its southern part has been already described. The material of 

 these rolling and hilly belts is generally till, containing more numerous 

 boulders and a larger proportion of small stones and gravel than in its 

 smoother tracts. The morainic swells and hills in this county rarely show 

 any uniformity or system in their trends; but the lakes in the southern 

 townships are quite noticeably elongated from east to west, thus trending 

 in parallelism with the course of the moraine there. Modified drift is oc- 

 casionally found within these areas, as was seen at the southeast edge of 

 the village of Waterville, where a cut on a hill-side to the depth of 

 twenty feet, having its top forty feet above lake Sakata, is sand and fine 

 gravel obliquely and irregularly stratified, as in kames. 



The broad belt of morainic drift upon the east side of this county and 

 in Rice county is a compound formation, consisting of the eastern marginal 

 deposits of the Minnesota lobe of the last ice-sheet, accumulated while this 

 side of the ice-lobe remained nearly stationary through a long time, during 

 which its southern and western border had formed five distinct moraines 



