The velocities here given represent mid-depth velocities on the subdivisions of the cross-section, counting from the left to the right shore. The following table shows the actual discharges at the time of observation, together with the stage of water above low-water of 1867:

Reducing the areas of cross-sections to low-water, but retaining the mid-depth velocities obtained, the resulting discharges are so much in excess of those obtained at corresponding localities during low water of 1867 as to render such procedure altogether valueless. This proves that mid-depth velocities are materially affected by comparatively insignificant changes in the stage of water. I must here state, also, that in shallow streams, like the Illinois, the effect of wind upon mid-depth floats is very considerably greater than it was found to be on the Lower Mississippi, as stated in the "Report upon the Physics and Hydraulics of the Mississippi River." Direct observations have shown that on the Illinois River every breeze affected the floats materially, both in direction and velocity. All observations made during a perceptible breeze were consequently rejected, and advantage was taken of every moment of perfect calm. The soundings were made on the plan adopted by the hydrographic party of 1867, the sounder lining himself by two flags set up on shore in the direction required.

Profiles of the soundings made, with the necessary reference lines of high and low water will be found on the maps accompanying this report.

BORINGS.

The borings at the several sites examined were necessarily of limited extent. As far as they went they merely proved what had been surmised before, that within twenty-four feet at least from the bed of the river no firm foundation can be found; and it is safe to predict that no better result will be obtained by boring to more than to twice that depth. The boring apparatus was made to order by a blacksmith in Keokuk, and will be best explained by the sketch in original manuscript.

The borer proper was made of one-inch square iron, forged at the foot into the shape shown in the sketch, and ten feet long.

Two more lengths of the same one-inch iron rod, each ten feet long, were made to join the borer by a connection as shown in the figure, bulging slightly beyond the thickness of the rod, so as to allow an iron jacket to be driven firmly over the joint by a few taps with a hammer. Two iron sockets to receive wooden levers were movably attached to the rods by a jacket and screw. To a depth of twenty-four feet this apparatus was found to work well, at an average rate of about five feet per hour, worked by two men.

Willow Island site.-The site selected for this dam is about midway between the foot of Willow Island and the town of Henry, a short distance below the mouth of Senachewine Lake. The width of the river

here is six hundred and sixty feet; the left bank where the lock should be located, thirteen feet above low-water, but the ground is rapidly sloping towards the interior to five and a half feet. The wet marsh midway between the left shore and the bluff is more than three feet higher than the dry ground intervening between it and the river. The right shore presents a gradual slope of compact gravel back one hundred feet to the foot of the gravel terrace, which extends from the lower outlet of Senachewine Lake to Henry, fifty-five to fifty-nine feet above low water. This terrace is composed of clay and gravel in about equal proportions, with some larger boulders near the base.

The dam for part of the way would be in a depth of fourteen feet at low water, with a gravel bottom for about half its length, and mud the other half.

The location of a lock and dam at the foot of Willow Island, as at first projected, is open to several grave objections. The channel above this place, on either side of the island, is perfectly straight, affording no protection from anything that may come down the river. The right bank is too low to meet the views expressed above, being but seven feet above low water. The outlet of Senachewine Lake is but a short distance below this site, and its connections with the river above are numerous, although only occurring at high water.

A more desirable site than this would have been at the foot of Henry Bar, a short distance above the town of Henry, and below the mouth of Sandy Creek. The river here is narrow, about six hundred and fifty feet wide, with a depth of five feet, gravelly slope, and gravel terrace on the right bank, and a clay slope ten feet high on the left. For a dam location it would probably be superior to the one selected, with the additonal advantage of submerging Henry Bar; but for a lock site the latter presents far greater advantages. I have not found a place near Henry on either shore, where a lock would not be exposed to the full sweep of the current. A sketch of this vicinity, taken from the maps furnished by the hydrographic party of the survey of 1867, will be found among the other maps of the Willow Island site on sheet No. 1.

Copperas Creek site.-The site chosen for the Copperas Creek lock and dam is at station N, (see sheet No. 2,) the lock to be located on the west shore. Both banks here are firm, gradually sloping, and about ten feet above low water. The west shore is free from danger of ice. The principal objection to this site is the shallowness of the water, 3.4 feet being the greatest depth at low water, but this may be balanced by the unusually firm character of the river-bed, which is, with the exception of a short distance from the west shore, composed of gravel all the way to the opposite shore, mixed with some shells and sand. Another objection, which is, however, common in a greater or less degree to all sites that can be chosen anywhere on the river, is the presence of a very large lake (Spring Lake) along the eastern border, with a main outlet below the site, and several smaller ones above it. Another site was therefore examined below the main outlet of Spring Lake. The borings made in the river-bed near the western shore reveal nothing but a bed of blue plastic clay, apparently quite free from sand, and very tenacious; twenty-four feet were bored through without any change. A specimen was preserved from a depth of twenty-four feet below the bottom. The dam would be six hundred and eighty feet long, timber for which can be obtained in abundance on either shore. Rock for filling will have to be floated down from above.

The bluff on the west side is mainly composed of drift, (loam, sand, and some slight indications of gravel,) and is on an average one hundred

and thirty feet high above water. At the foot of the bluff, in the bed of Copperas Creek, some twenty feet of coal shale were found, containing a thin bed of impure coal and bituminous slate. The lower portion of the shale is seamed with nodules of clay-ironstone, resembling very much those found on Macon Creek, near Morris, renowned for the paleontological treasures they contain, but no fossils were found at this locality, except some indistinct flattened shells in the shales, among which a Chonetes mesoloba. Large blocks of drift conglomerate, quite hard and compact, were found overlying these coal-measure beds, very similar to those of Hennepin and Peoria. A section of this locality will be found on sheet No. 2.

Spring Lake.-As an alternate for the Copperas Creek site, another location, below the mouth of Spring Lake, was examined. The only safe site was found at the Liverpool Ferry Landing, where the river is contracted to a width of four hundred and eighty feet. The left bank here is thirteen feet high, sloping towards the interior to an average level of seven and one-half feet above low water, a rather desolate region, with plenty of marsh, and an almost impenetrable jungle of cockle-burs. The bottom is bounded by a sand ridge or terrace sixty-two feet above low water, and covered with small black-jack, distant from the river one and quarter mile. The right bank at Liverpool slopes gradually to twenty feet above low water, while the marsh in the interior is but six feet above low water. The bluff, two and a quarter miles back from the river, is one hundred and forty-four feet high; its base consists of coalmeasure shales, thirty feet or more in thickness. No other rock observed.

The objection raised against the Copperas Creek site, on account of the shallowness of water, certainly does not apply here, with a depth of eighteen and a half feet above low water. There are lakes and marshes on both sides of the river; the bed of the river consists of soft mud on the eastern half, and gravel and mud on the western.

No borings were made, as the boring apparatus would only reach twenty-five feet, twenty of which would have been occupied by water.

Frederick.-At Frederick the west bank, about one hundred feet from the edge of the water, is twelve feet above low water, rising to thirty feet at the town of Frederick. The bluff is distant from the river onehalf mile and two hundred and thirty feet high. The top of the mound at its summit is two hundred and thirty-eight feet high. The base of the bluff is formed of four feet of bluff and blue limestone, containing some large conularia overlaid by blue sandy shale of the coal measures. For fifteen feet above this the drift loam is stratified with horizontal seams of pebbles and small boulders; the rest of the bluff consists of unstratified loam, sandy towards the top.

The east bank, opposite Frederick, is low, strongly abraded, and the exposed trees show heavy ice-marks. The site selected for a lock and dam is at station H, (see sheet No. 4,) where the river is six hundred and sixty feet wide, its greatest depth at low water six feet, with sandy bottom throughout.

The borings in the river-bed reveal the usual mixture of a great deal of sand with some little black mud. The west bank is fourteen and a half feet high, with a gradual slope, and quite firm. The prairie, six hundred feet back of the river, is eleven feet above low water, and extends to the bluff some two miles distant. The east bank is twelve feet above low water; but the distance between the river and Beardstown Bay, fourteen hundred feet, is traversed by smaller sloughs parallel to the river, and only four or five feet above low water.

The town of Beardstown is from twenty-two to twenty-six feet above low water; the soil is very sandy. The river bottom here is five and a half miles wide, almost all of it above high water, and intersected by numerous sand ridges. The bluff is two hundred and thirty-three feet high, the mound on its summit two hundred and forty-two feet. At an elevation of one hundred and thirty-four feet, there is an outcrop of fine-grained buff sandstone with some shales. The sandstone is similar in character to that at Lagrange, overlying the limestone and coal. No survey was made above Frederick to Sugar Creek, because reconnaissance had shown the left bank for all that distance to be too strongly and abruptly abraded.

Abundance of rock for filling cribs can be obtained from Sugar Creek, which during high water is navigable for medium-sized flats up to the limestone quarries. The rock is not fit for heavy masonry.

Lagrange. The best site for a lock and dam in this vicinity is found directly in front of Lagrange, at Station 5, (see sheet No. 5.) The river here is six hundred and sixty feet wide at low water, eight hundred and sixty-five between banks. The greatest depth is found close to the east shore, where the lock should be located, 7.3 feet at low water; but the river is quite shallow for four-fifths the distance across.

The west bank is twelve feet above low water at sixty feet from the water's edge, rising to forty feet at the foot of the bluff, eleven hundred and fifty feet from shore. The bluff, containing coal at an elevation of ninety-six feet, is two hundred and seventy-eight feet high. The coal has been worked in numerous pits, but does not appear to be of very good quality.

The east bank is eleven feet above low water, with a gradual and` easy slope, and firm soil, but immediately descends to a slough, seven feet above low water, and at a distance of eight hundred feet to a lake, the water of which is at nearly the same elevation with that of the river. The outlet of this lake is but a short distance below the proposed location.

Naples. The only acceptable location for a lock and dam in this neighborhood was found at Station 6, (see sheet No. 6,) a short distance below the wharf at Naples. The river here is eight hundred and ninetythree feet wide; at low water, its greatest depth, 6.6 feet; and the bottom consists mostly of sand and hard material, gravel and shells, with some mud. The west bank is firm and gradually sloping, 12.2 feet above low water. The lake, one-fourth of a mile back from the river, is nine feet above low water; the general level of the prairie extending to the bluff is eleven feet, rising to eighteen feet nearer to the foot of the bluff where the land is cultivated.

The elevation of the foot of the bluff, two and one-fourth mile distant from the river, is twenty-one feet; that of its summit, two hundred and three feet. At an elevation of sixty feet an outcrop of thin-bedded limestone was observed; no other rock visible.

The east bank is sandy, and slopes gradually, for a distance of sixtyeight feet, to an elevation of fifteen feet, then rises, almost perpendicu larly, four feet. The abrasion here is very strong, but can only be caused by high water. Thence the land is apparently a dead level at an elevation of nineteen feet, for a distance of about two thousand feet; in fact, with the exception of a slight depression or slough immediately back of the town, virtually a level back to the foot of the bluff, a distance of about four miles.

The bluff directly above Naples is composed of sand throughout, regularly stratified in its steep escarpments. For about one hundred feet

from the edge of the water it slopes gradually to an elevation of fifteen feet, thence very abruptly, and in some places nearly perpendicularly, to thirty-five feet. The average height is forty-six feet; the highest point, fifty-four feet. To the landward it slopes gradually to the general level of the bottom lands. The elevation of this ancient sand-bar furnishes us with the approximate height of the Illinois River at the time when it filled its wide valley.

Bedford.-Considerable difficulty was experienced to find a site near Bedford that would at all answer even the modest requirements proposed. A site was at length determined on at Station 10, (see sheet No. 7,) as presenting the least objections.

The river here is, at low water, nine hundred and eighty-six feet wide; its greatest depth, seven and one-half feet; the bottom, about one-half mud and one-half gravel and shells.

The west bank is firm, gradually sloping and about thirteen feet above low water, gradually rising to the foot of the bluff, one-fourth mile distant. The bottom is well timbered and dry. The bluff here is formed of massive beds of light-colored, semi-crystalline limestone, at least seventy feet in thickness, presenting high perpendicular escarpments, and altogether the most picturesque views to be found anywhere on the lower Illinois. Pilot peak is the most remarkable of these. The summits are dotted with mounds, some of them of considerable dimensions, and it cannot be denied that whatever races built these, the only remaining traces of their existence, they must have had an eye to natural beauty, as the mounds are invariably found wherever the prospect is fine and extensive.

The east bank, at the site selected, is less favorable than the western, being about ten feet above low water, and a deep though dry slough running parallel with the shore, within two hundred and fifty feet, frequently communicating with the river by shallow outlets. The timber is heavy, with a dense undergrowth, and impenetrable, except at the driest season, and then only at an expense of time which we could not afford.

In order to obtain a fair idea of the river bottom, a cross-section was made a short distance above Bedford. On the west bank the ground rises rapidly to the foot of the bluff, which is here close to the river, and rises to a height of two hundred and eighty feet. On the east side the bank is fifteen feet above low water, and after crossing a marshy run, emptying into the river at the head of Shin Island, a wide prairie is reached, elevated thirteen and a half feet above low water, and intersected by narrow marshes, which unite a short distance below into a very extensive marsh or lake. The bluff on this side, two and a half miles from the river, is one hundred and ninety feet high, (the mound on its summit two hundred feet,) and is composed altogether of loam, very precipitous, and cut up by deep ravines, perfectly bare of timber, except on the summit.

The width of the valley between the tops of the bluffs is 3.2 miles. The unusual severity with which the winter set in after the completion of the Bedford survey rendered it impossible to undertake the examination of the only remaining site, that near Six-mile Island. A more extended time and a more favorable season might probably have enabled us to find some more favorable locations for the construction of locks and dams than those herein reported on. But from a rather familiar acquaintance with the Illinois River, I can say without hesitation that I do not consider that river at all adapted to slack-water navigation. This mode of improvement should only be resorted to where all other