HISTOBICAL SKETCH. 39 



1833, Keating.] 



must have been a confused one. Tourmaline is found disseminated throughout the rock, yet in no 

 great abundance. In one or two spots where the mass assumed a more slaty appearance than in 

 other places a faint tendency to a stratification, directed from the north-northeast to the south- 

 southwest, with a dip toward the south, was observed. Viewing the insulated masses from the 

 prairie, they appeared to be directed in a transverse line through the valley, and in a northeast- 

 erly course, so that this may be the remains of a dike which existed across the valley, but 

 which was finally broken. This observation was, however, a partial one, and it would be improper 

 to attach much weight to it. When calling the attention of our guide to the difference between 

 these rocks and those observed below, he appeared to have been aware of it himself, and stated 

 that rock similar to these extended down the valley to about four miles below Kedwood rivulet. 

 It was partly from this circumstance that we inferred that Patterson's rapids were probably 

 formed by a bar of these rocks rising across the bed of the river. This appeared to us to be the 

 more probable from the circumstance that a rapid known by the name of the Little falls, occurs 

 just above the place of our encampment of the 18th, and that it is occasioned by a ledge of granite 

 rocks over which the river passes at this place. In the examination of this spot two points 

 appeared to us chiefly to deserve our attention, in order to avoid all source of error; the first was 

 to ascertain that the rocks were really in situ ; the second, that they were primitive and crystalline, 

 not conglomerated or regenerated rocks, such as are sometimes observed. But upon these two 

 points we think that not the least doubt can be entertained. The immense mass of these 

 insulated rocks, the uniform bight to which they attain, the uniform direction in which they lie, 

 prove them to be in place ; while an attentive inspection of their nature shows them to be really 

 crystalline. There is a gradual, though rapid, passage of the granite into the sienite, which 

 proves them to be of contemporaneous formation, and which precludes the idea that the rock is 

 formed by the union of fragments of granite, sienite, &c., cemented together. 



The discovery of this granitic formation here appeared the more interesting, as its small 

 extent might easily have prevented us from observing it. had not chance brought us to the river 

 at this place ; for if we had been traveling on the prairie, within half a mile of the edge of the 

 bank, the greater hight of the bluff would have concealed these rocky islands from our view. 

 We feel, therefore, unable to decide whether they do not occur at some other bends of the river 

 which we avoided ; yet from the character of the stream itself we doubt it. For we find that as 

 soon as these rocks protrude into the valley, they occasion rapids and falls in the river, while other- 

 wise its course is smooth. Had we not seen the " Little rapids ", which we passed on the llth, 

 we might have been induced to consider them as resulting from the appearance of the primitive 

 rocks at the surface, but having examined with care the sandstone rocks, by which they are pro- 

 duced, and having ascertained that no other rapids are found in the St. Peter, between these and 

 the Patterson falls, we are induced to believe that this is the only place where granite may be seen 

 in situ. In attempting to connect this primitive formation with those observed elsewhere, we find 

 that it lies in a direction about W. S. W.. at a distance probably not exceeding eighty miles, of the 

 "granitic and hornblendic rocks" which Mr. Schoolcraft states as having seen "occasionally rising 

 in rugged peaks and beds" on the Mississippi.* We feel , however, disposed to consider all this 

 section of our country as reposing on this granite, and we entertain but little doubt of its identity 

 with the sienitic granite observed at a later period of our journey, and which we first struck near 

 fort Alexander at the mouth of the Winnipeek river. 



Subsequently Mr. Keating observed that these rocks, which were made 

 out to be in latitude 44 41' 26" N., did not extend far in the valley. The 

 last of them were seen at about four miles above the little falls, and he 

 was assured by the guide that they did not recur for a considerable distance. 

 Still he observed, at a distance, a rocky island in the bed of the river, which 

 had the same kind of rock as that at Patterson's rapids; and again at points 

 further up the valley rocky knolls were observed. 



'Schoolcraft's Narrative, p. 288. 



