OF WISCONSIN AND 



MINNESOTA. 



103 



■with a slight fall, set in, three and a half miles above the mouth of Kettle River. 

 At the head of these I noticed the first range of trap unequivocally in place. 

 It is of a cuboidal, or almost columnar structure ; some of it is quite dark-coloured, 

 almost black, with ferruginous stains ; other portions are dark green and brown. 

 A few hundred yards below this exposure, on the south side of the St. Croix, 

 red sandstone is in place in a very shattered condition, resting on a conglome- 

 rate, which is slightly calcareous, its aspect having much the appearance of the 

 Potomac marble, but the fragments of which it is composed are siliceous, with only 

 a small proportion of calcareous cement. At a bend just below is a protrusion of 

 trap, crossing the river obliquely, with a bearing nearly east^northeast and west- 

 southwest. The upheaval of the trap has caused rapids here in the river, and has 

 shattered the superincumbent beds, which are in a very broken condition. Below 

 the bend on the same rapids, trap is in place, and can be traced to the height of 

 fifteen to twenty feet above the river bed in the adjoining bank. The igneous out- 

 burst on this part of the St. Croix has not been sufficient to produce hills of any 

 great elevation, twenty or thirty feet being the general height of the ridges here. 

 Part of the rock of this range has an amygdaloidal structure. 



This is doubtless the same trap range which Mr. J. Evans's party found crossing 

 Kettle River, a few miles above its confluence with the St. Croix, and where some 

 copper boulders have been found. 



Three and a half miles below Kettle River, Snake River disembogues, on the 

 west side ; and one and a half to two miles further, horizontal strata of white and 

 light yellow sandstones appear, fifteen feet above the river, on the east side of the 

 St. Croix, covered with twenty to twenty-five feet of drift. No organic remains 

 were discovered in these sandstones by which to determine their age ; but the 

 lithological character is like that of the sandstones of the Mississippi, and does not 

 possess the red colour and argillaceous character of the sandstone three miles above 

 Kettle River. The most southern limit of the red sandstones like those of Lake 

 Superior, must be somewhere in the vicinity of Snake or Kettle Rivers. This 

 member of F. 1, extends, therefore, much further down the valley of the St. Croix 

 than down that of the other tributaries of the Mississippi. Its southern boundaiy, 

 in a direct line, cannot be here over sixty miles from the Mississippi River. 



Similar sandstones to those mentioned above, as occurring two miles below Snake 

 River, are exposed at intervals, for the distance of several miles below, on the banks 

 of the St. Croix. About eight miles below this first exposure, there is an outcrop 

 on both shores ; on the east side they are weathered into low arches. Some fine 

 springs issue from the bank a few miles further ; these are the first cool springs of 

 water that we have noticed in our descent of the St. Croix. 



Below this, no rock exposures were observed immediately on the river, only trap 

 boulders occasionally lining the shores. 



On both sides of the river, above Rising Sun, are some fine sites for farms ; the 

 ground is level, and the soil light, but rather siliceous. 



Eight or ten miles below Rising Sun, the pines are replaced by a growth of hard 

 wood. 



