ON THE MINNESOTA RIVER, 



491 



nearly two miles ; the third, the upland prairie, which has a further elevation of 

 forty to sixty feet, and in some places is still higher. 



At some points on the St. Peter's, in place of the first alluvial terrace, the prairie 

 ascends gradually from near the water's edge to the distance of some six hundred 

 yards, with hardly the least irregularity in the slope ; a portion of it, sparingly 

 timbered with small oaks, resembling at a distance a flourishing orchard. These 

 spots appear so like cultivated farms, that when, as is sometimes the case, a cliff of 

 rock can be discerned in the distance, partially concealed by the trees in the fore- 

 ground, the traveller almost fancies he has discovered the residence of the proprietor. 

 The second bench of land is sometimes strewn with erratics and shapeless blocks of 

 indurated sandstone, derived from some of the neighbouring cliffs. 



Nearly opposite the mouth of the Waraju, is an exposure of altered sandstones 

 and conglomerate, dipping towards the north at angles varying from 15° to 30°. 

 The whole height of the inclined strata is one hundred and ten feet. At the base 

 are layers of compact sandstone, of a brick-red colour, which split readily into 

 laminae of variable thickness. Some of these lamina) are ripple-marked, and 

 resemble specimens brought from near the head of the Menomonie River.* 

 Their thickness is fifteen feet. Reposing on these are metamorphic sandstones of 

 various degrees of induration and colour. Some portions are soft and friable, and, in 

 lithological appearance, do not differ materially from the beds of F. 1, observed in 

 other parts of the valley of the St. Peter's, while other portions are completely 

 metamorphosed into an exceedingly compact quartzite, of a brick or mahogany-red 

 colour. Towards the summit of the ledge are numerous " pot-holes," the sides and 

 bottoms of which were worn smooth, and even polished. The largest of these was 

 found to measure two feet and a half in depth, by two feet in diameter. The bear- 

 ing of the strata runs nearly east and west. 



About one mile in a straight line above the mouth of the Waraju, and three by 

 the course of the river, we found some outliers of coarse conglomerate and granite, 

 a short distance from the bank of the stream. The conglomerate is composed 

 mainly of quartz pebbles and boulders, some of the latter ten inches in diameter ; 

 the whole cemented with a siliceous material. Its elevation above the level of the 

 prairie is about ten feet. The course of the exposure is nearly east and west, with 

 a dip towards the south of 20°. The granite is a hundred yards removed from the 

 conglomerate, with its line of elevation running nearly parallel with the latter. 

 Flesh-coloured felspar forms nearly two-thirds of the granite. 



The rocks do not appear again in situ until we reached La Petite Roche, which 

 is estimated to be about twenty-five miles above the mouth of the Waraju River. 

 Here, again, granite occurs mixed with syenite, elevated between seventy-five and 

 a hundred feet above the level of the river. The granite is highly crystalline, and 

 is traversed by numerous cleavage-planes, which cause it to separate with readi- 

 ness into angular blocks and slabs. The mineral hornblende constitutes at least 

 four-fifths of the syenite ; felspar predominates in the granite. 



Half a mile above La Petite Roche, a mass of granite occurs in the middle of the 



* A thin seam of red pipestone runs between some of the layers. 



