BORDERING ON THE WISCONSIN RIVER. 293 
be considered the head of steamboat navigation on this river. Occasionally, fine 
sections of sandstone were displayed in the blufts to-day, rising from thirty to one 
hundred feet above the water-level. 
A short distance above Sauk Prairie, I noticed, for the first time on this route, 
the Lower Magnesian Limestone, overlying the sand-rock, which reaches, in the course 
of the river, from Whitney’s Rapids to this place. At the junction of the two 
rocks, they present a very peculiar banded appearance, when exposed in mural 
cliffs, owing to the intercalation of thin layers of the two formations, and their wea- 
thering unequally. : 
At this point my geological observations ceased ; the object of the reconnoissance 
having been to trace the rocks from Lake Superior to their junction with the Pro- 
tozoic Sandstone of the Mississippi Valley, and make incidental observations on the 
topography of the country. Having accomplished these objects to the best of my 
abilities, I hastened toward the rendezvous at Prairie du Chien, where we arrived 
on the morning of the 19th October. 
SECTION III. 
NARRATIVE OF EXPLORATIONS MADE IN 1848, ALONG A PORTION OF THE NORTH SHORE OF LAKE 
SUPERIOR, AND ON LEFT-HAND, ST. LOUIS, UPPER EMBARRAS, VERMILION, RAINY LAKE, BIG FORK, 
AND THE NORTHERN MISSISSIPPI RIVERS. 
On the 10th of June, I received, at the mouth of Crow Wing River, your final 
instructions, regarding my field of operations for the season, and the nature of the 
reconnoissance to be made along the north shore of Lake Superior. As tlie geography 
of the northern portion of the District was but little known, and as the geological 
exploration of this country would be far in advance of the linear surveys, the Depart- 
ment had determined to have the position of important points determined, as nearly 
as might be, by astronomical observations with the sextant and chronometer. This 
especial duty was assigned to Colonel Charles Whittlesey, the result of whose labours 
has already been communicated to you. 
We were detained at the mouth of Crow Wing River nearly a week after your 
departure for Red River of the North, in consequence of our inability to procure 
canoes and a sufficient number of voyageurs. Our first intention was to ascend the 
Mississippi to Cass Lake, and proceed thence to Rainy Lake, by way of Red Lake; 
and from that point to cross the country to Lake Superior, by way of Vermilion 
Lake. But, on making an estimate of the length of time which would be required 
for such a journey, it was obvious that the small lot of provisions we had brought 
with us would not last beyond Rainy Lake River. As there was little probability 
of our being able to obtain supplies at either Red Lake or Rainy Lake River (which 
we subsequently ascertained we could not have done), and none could be procured 
at Crow Wing, we determined to reverse the projected line of exploration, and pro- 
ceed immediately to Lake Superior; and, after having made a reconnoissance of 
that portion of the north shore of the Lake designated in my instructions, to pro- 
