About five o’clock we came to a high diluvial ridge of gravel and sand, mixed with boulders of syenite, trap-rock, quartz, and sandstone.  Ozawandib, our guide, said we were near the junction of the Naiwa, or Copper-snake River, the principal tributary of this branch of the Mississippi, and that it was necessary to make a passage over this ridge to avoid a formidable series of rapids.  Our track lay across a peninsula.  This occupied the remainder of the day, and we encamped on the banks of the stream above the rapids and pitched our tent, before daylight had finally departed.  The position of the sun, in this latitude, it must be recollected, is protracted, very perceptibly, above the horizon.  We ascended to the summit in a series of geological steps or plateaux.  There is but little perceptible rise from the Cross-water level to this point—­called Agate Rapids and Portage, from the occurrence of this mineral in the drift.  The descent of water at this place cannot be less than seventy feet.  On resuming the journey the next morning (13th) we found the water above these rapids had almost the appearance of a dead level.  The current is very gentle; and, by its diminished volume, denotes clearly the absence of the contributions from the Naiwa.  About seven miles above the Agate Portage we entered Lake Assawa, which our Indian guide informed us was the source of this branch.  We were precisely twenty minutes in passing through it, with the full force of paddles.  It receives two small inlets, the most southerly of which we entered, and the canoes soon stuck fast, amidst aquatic plants, on a boggy shore.  I did not know, for a moment, the cause of our having grounded, till Ozawandib exclaimed, “O-um-a, mikun-na!” here is the portage!  We were at the Southern flanks of the diluvial hills, called HAUTEUR DES TERRES—­a geological formation of drift materials, which form one of the continental water-sheds, dividing the streams tributary to the Gulf of Mexico, from those of Hudson’s Bay.  He described the portage as consisting of twelve pug-gi-de-nun, or resting places, where the men are temporarily eased of their burdens.  This was indefinite, depending on the measure of a man’s strength to carry.  Not only our baggage, but the canoes were to be carried.  After taking breakfast, on the nearest dry ground, the different back-loads for the men were prepared.  Ozawandib threw my canoe over his shoulders and led the way.  The rest followed, with their appointed loads.  I charged myself with a spy-glass, strapped, and portfolio.  Dr. Houghton carried a plant press.  Each one had something, and the men toiled with five canoes, Our provisions, beds, tent, &c.  The path was one of the most intricate and tangled that I ever knew.  Tornadoes appeared to have cast down the trees in every direction.  A soft spongy mass, that gave way under the tread, covered the interstices between the fallen timber.  The toil and fatigue were incessant.  At length we ascended the first