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October 12. – There was a light fall of snow last night, and the sprinkling of pure white on almost every variety and shade of color of autumnal foliage, intermingled with evergreens, combined with the wooded island in the distance, the rapids with their rocky projections in the foreground, and the dense forest on either shore, to make up one of the most picturesque and fairy-like scenes imaginable.

The river, for some distance below this point, is full of rock islands, rising from ten to fifteen feet above the water level, and made up of a reddish colored rock, composed of quartz and feldspar, bearing northeast and southwest, with a dip of 39° to the southeast.

About eight miles below the camp of last night, we reached Whitney's rapids; the rock, during the whole distance, being a feldspathic granite, with little or no appearance of mica in its composition; and, as the rapids are approached, showing a great disposition to decompose on exposure to atmospheric influence.

The last exposure of granite on Wisconsin river is seen a short distance above the old mill dam, at these rapids, and extends down the river for the distance of a quarter of a mile, gradually becoming more quartzose in character, and at the point where it disappears is traversed by many feldspathic veins, from one to eight inches wide, having a northwest and southeast direction.

Above the granite at the old mill dam is a bed of ferruginous argillite, four feet thick, succeeded by five feet of decomposing feldspar, above which is a bed, two feet thick, of well digested kaolin, or porcelain clay, with large amorphous crystals of quartz disseminated through it in veins, and containing a notable quantity of pyrites. Then succeeds a variegated white and yellow sandstone in their laminae, from the sixteenth of an inch to an inch in thickness, rather coarse grained, somewhat micaceous and weathering easily. Some of the laminae are green, and the whole dips 4° to the southeast.

A quarter of a mile below the old dam, on the east side of the river, the sandstone forms a mural escarpment of thirty-five feet in height, in strata of from two to eight feet thick. On the west bank, opposite this section of sandstone, the most southerly exposure of crystalline rocks on this river rises to the height of six feet above the water, and is composed of a quartzose granite, containing magnetic oxide of iron.

Two miles below Whitney's rapids is the foundation of a town called "Point Boss," consisting, at present, however, of only two houses. This is a somewhat important place, in a geological point of view, as it is situated near the margin of the great sand region where it crosses Wisconsin river.

October 13. – At 1 o'clock we reached Petenwell Peak, thirty-two miles below Point Boss. The country between these two points resembles, in almost every respect, that seen below the Dalles of the Chippewa River. The river winds through sands, rising forty and sixty feet above its level, and presenting in its bends extensive slides, from a quarter to half a mile in length. It is very crooked, and the channel rendered somewhat intricate by the great number of sandbars, which change their position with every rise and fall of the river. Not a boulder, nor scarcely a pebble, is to be seen after passing the first ten miles below Whitney's rapids; showing, conclusively, that the forces which transported the immense numbers of erratic blocks, met with in other sections of the territory, did not tend in this direction. Like the region alluded to on the Chippewa, the country is a succession of sand plains, rising in low steppes, covered with a short coarse grass, and having a few small pines and shrubby oaks scattered over it.

About half a mile before reaching Petenwell Peak, that huge mass of rock suddenly presented itself down a reach of the river, rising above the level sands to the height of two hundred feet, or more, and presenting, in every respect, the semblance of a work of human hands, now dilapidated and in ruins. It required no excited imagination to see, in this extraordinary mass of rock, the remains of some ancient stronghold. There were the massive walls, defined and regular in their outline, battlements, towers, buttresses, surmounted by towering pinnacles, deep, dark windows, and, in short, everything necessary to render the delusion perfect.

The base of the peak is an oval, about three hundred yards in the long, and one hundred yards in the short, diameter. On the east side, the rock is almost perpendicular, and is washed at its base by the river. On the north side, a small creek comes in from the west, close to the rock. On the south and west sides, there is a very abrupt slope from two-thirds the height of the rock to the general level. This slope is made up of sand and huge fragments of stone, with small pines scattered among them. The upper third is a perpendicular wall of rock, split into towers and turrets, and which I found it impossible to ascend. The prospect from the point which I reached is very extensive, embracing an expanse of country probably from forty to fifty miles in diameter.

The general appearance of the country from this elevation is that of a level or gently undulating plain, dotted here and there with forests of small oak and pine. But on every side, as far as vision can reach, other isolated peaks are seen rising from the plain. One towards the northeast, and distant probably twelve or fifteen miles, is apparently higher than Petenwell; and others, in different directions, from their appearance in the distance, no doubt equal it in height. To the southwest, on the verge of the horizon, there appears to be a connected chain of hills. In no other direction, however, is there the slightest appearance of connexion between the elevated masses, each one standing "solitary and alone," and. miles from its fellows.

The rock is a light colored, coarse grained sandstone, made up of perfectly rounded grains, many of which are limpid quartz, and cemented together with considerable firmness. Some of the strata are banded with white and brownish yellow stripes.

About six miles below Petenwell Peak, there is an exposure of fourteen or fifteen feet of sandstone, in the east bank of the river. Seen from a distance, it reminded me forcibly of the "pillared rocks" of Lake Superior. Some of the layers are soft and friable, while others are hard, and weather with difficulty. The current of the river, which continually washes the rock, has cut away the softer layers, leaving the harder ones standing out in relief, in the shape of rude cornices, while the rills produced by rains falling on the sandy slope above, and trickling down the rock at intervals of from five to twenty feet, have divided the cornices into capitals, and the rock below into pillars, so that it has, when seen from a distance, altogether the appearance of a magnificent colonnade, nearly a quarter of a mile in length, with the base of the columns resting in the water. There is a great difference in one respect, however, between the pillared rocks of the lake and those of the Wisconsin. While the first, generally small in diameter and graceful in form, support an entablature often forty or fifty feet in depth, and crowned with noble forest trees; the latter, huge and massive in proportions, are capped by three or four feet of sand, bearing a few stunted shrubs, as worthless as the soil from which they spring.

October 14. – Nine miles below the last exposure of rock, thin shaly layers of sandstone appear just above the margin of the river, for the distance of half a mile. And four miles further, the rock rises to the height of twenty-five feet, in layers from six inches to five feet in thickness, variegated with red and yellow bands, and having very soft pulverulent nodules of oxide of iron, as large as walnuts, disseminated through some of the layers. The rock dips 4° to the southeast, is rather fine grained, and contains a considerable proportion of greenish colored grains, not, however, in sufficient quantity to impart a greenish hue to any of the layers.

Two miles below this place, Fortification Rock rises to the height of more than a hundred feet above the general level. It stands on the west bank, about one hundred yards from the main channel of the river. The northwest side, which is one hundred and twenty feet long, is perpendicular, while it descends, on the southeast side, by a succession of narrow terraces, to the general level. The top presents an almost unbroken outline, while the front has singularly weathered, at a number of points, into semblances of windows and loopholes.

Below this place, the rocks are almost constantly exposed, on one or the other side of the river, rising to the height of forty or fifty feet, sometimes pillared, generally mural, and with a constant dip to the southeast of from 3° to 4°. Some of the strata are laminated, and present a very remarkable appearance; the angle formed by the joints of the lamin and those of stratification, ranging from from 10° to 23°. In some of the layers, the laminae are parallel with the plane of stratification; in some they are waved, and in others oblique; in some the materials are fine, in others coarse; showing the changeable direction and force of the currents by which they were deposited. I observed strata of precisely the same character in the sandstone of Chippewa river, and occupying, apparently, the same position in the series.

At 2 o'clock, we reached the chain of hills descried from Petenwell Peak. They consist of sandstone of the same character with that seen yesterday and to-day, with the exception of the upper layers, which, for the thickness of twenty-five or thirty feet, are white and sugar-like, and when struck with the hammer crumble into sand, rendering it somewhat difficult to procure and transport specimens. These cliffs differ from those seen yesterday, in presenting on one side a nearly perpendicular face, from two hundred to three hundred feet high, while on the opposite side they descend, by long and very gradual slopes, to the general level. They rise at long intervals, being separated by wide ravines, sparsely wooded, and are distributed along the country like a cordon of forts. Many, indeed most of them, resemble, when seen from a distance, artificial works, and one who has seen them feels no surprise that the superstitious Indian should consider them dwelling places of superior intelligences, and look upon them with awe and reverence. Although the materials of which they are composed possess little coherence, and are separable by a slight force, they will resist the siege of the elements for centuries yet, and remain to mark the boundaries of cultivation, which can never encroach upon the sterile wastes encircled by them.

Two miles further brought us to the Dalles of the Wisconsin. The walls of sandstone forming the Dalles are from twenty-five to eighty feet in height, and from fifty to one hundred feet apart Between these perpendicular walls the river flows for some five or six miles, its average width being about one hundred feet.

Although it is quite as low as it was ever known, scarcely affording, in many places, sufficient water to float a canoe, in the Dalles it is deep, and the shadows of the rocks give the water almost black appearance. The current was gentle, and often almost imperceptible, and the bed, so far as I could judge, is free from loose masses of rock. When the river is high, and especially during freshets, it is a passage of great dread to the "raftsmen," in consequence of the many short turns and projecting points around which the raft is swiftly hurried by the current, which then forces its way through the long defile with the speed of an arrow, being greatly accelerated by the great head of which accumulate above the entrance, forming quite a lake, and pressing to enter the narrow gorge.

The weathering of the laminated strata before alluded to, with their exposure to the action of the current in different directions, and the cutting of the joints in varying lines, are productive of singular and beautiful effects. Architraves, sculptured cornices, moulded capitals, scrolls, and fluted columns are seen on every hand; presenting, altogether, a mixture of the grand, the beautiful, and the fantastic.

The dip of the rooks here is 3° to the southeast. The country is rolling, and the sands are covered by a thin soil, supporting a growth of small oaks.

October 15. – Eighteen miles below the Dalles, we passed " Winnebago Portage," which leads to Fox river of Green bay, and was, for many years, the route by which all the goods intended for the trading posts at Prairie du Chien, and other points on the Mississippi, passed, in their transportation from Mackinaw. It may be considered the head of steamboat navigation on this river. Occasionally, fine sections of sandstone were displayed in the bluffs to-day, rising from thirty to one hundred feet above the water level.

October 16. – At 11 o'clock to-day, we reached "Sauk Prairie," a village containing some fifty or sixty good houses. It is beautifully situated on the north bank of the river, and extends along the shore for nearly a mile. The houses are mostly substantial neatly painted homes, though there are several brick buildings, and I noticed a beautiful structure of magnesian limestone. The distance from this place to the mouth of the Wisconsin is about eighty miles.

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.

At this point my geological observations ceased; the object of the reconnoissance [sic] having been to trace the rocks from Lake Superior to their junction with the survey of 1839, 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.

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