BETWEEN ST. CROIX AND MISSISSIPPI 275 
of August, and on the morning of the 27th started on my return to Lake Superior, 
with the view of examining the eastern line of the District, from Lake Superior to 
its southern termination. In this reconnoissance I was accompanied by Mr. W. F. 
H. Gurley; and I take great pleasure in mentioning here his uniform gentlemanly 
deportment, and attention to the duties assigned him, while associated with me. 
We proceeded by land to the Falls of the St. Croix. At that place we procured 
a canoe, and ascended the river to Upper St. Croix Lake. From thence we made 
a portage to the head of the Bois Brulé, and descended that river to its mouth. 
Here we were detained two days by high winds, and then proceeded to Madeline 
Island, where we arrived on the 11th of September. 
During this journey I made a great number of barometrical observations, the re- 
sult of which is laid down on the plate of the profile of the country. 
I now subjoin a few observations on the geology of the St. Croix, in addition to 
those already made incidentally by yourself. 
In ascending that stream, exposures of white and drab-coloured sandstone are 
met with between the mouths of Rush and Wood Rivers. These rocks are coarse, 
slightly cemented, and disintegrate easily. Some of the layers are waved and thinly 
laminated, while others show cross-lines of deposition. Two miles above the mouth 
of Wood River, there is an exposure of twenty-five feet of the same rock. At this 
place the lower beds are thinner and softer than the upper ones, which are tole- 
rably compact, and variegated by horizontal stripes of a darker colour than the body 
of the rock. 
Opposite the first island above the mouth of Snake River, on the east side, is an 
exposure of shales and sandstone, underlying about forty feet of drift. The rock 
is in thin beds, of a greenish-gray colour, and intercalated with seams of bluish and 
deep-red indurated clays. The clay-beds are from four to eight inches thick. A 
short distance further up stream, these beds are capped by thirty feet of sandstone, 
exposed in the hillside in a mural escarpment. Immediately above this, on an 
island, trap shows itself; and five hundred yards higher up, beds of yellowish 
sandstone, with a red bed underneath, occurs in the east bank of the river, tilted 
up at an angle of 45°, and dipping to the southeast. In the bluffs, just above this 
place, is an exposure of thirty feet of drab-coloured sandstone. Nearly opposite the 
mouth of Kettle River, on the east side of the east chute, is an exposure of red 
brecciated conglomerate, the fragments and pebbles being all of red sandstone. 
The dip of the rock here is somewhat doubtful, but it appears to be to the north- 
west. 
Near the head of Kettle Rapids, on the main shore, a dark-red, fragmentary 
sandstone occurs, overlying a yellowish-coloured rock of the same kind, and show- 
ing every evidence of having been subjected to metamorphic influences. On an 
island in the Rapids, near by, is an exposure of No. 680, of considerable extent ; 
and at the head of the Rapids is a heavy trap dike, bearing northeasterly and 
southwesterly. Above the Rapids, on the west side of the river, the course of the 
dike is marked by a low ridge of angular fragments, and, as it extends south- 
westerly, by a number of islands in the stream. The exposures of drift in this 
vicinity, measure from thirty to fifty feet in height. 
