352 EXPKDITION TO THE 



throughout the rock, yet in no great abundance. In one 

 or two spots where the mass assumed a more slaty appear- 

 ance than in other places, a faint tendency to a stratifica- 

 tion, directed from north-north-east to south-south-west, 

 with a dip towards the south, was observed. Viewing the 

 insulated masses from the prairie, they appeared to be di- 

 rected in a transverse line through the valley, and in a 

 north-easterly 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 appear- 

 ed to have been aware of it himself, and stated that rocks 

 similar to these extended down the valley, to about four 

 miles below Redwood rivulet ; it was partly from thi: cir- 

 cumstance 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 pro- 

 bable 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 granitic rocks, over which the river passes at this 

 place. In the examination of this spot two points appear- 

 ed 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 

 height to which they attain, the uniform direction in which 

 they lie, prove them to be in place ; while an attentive in- 



