would not have been able to get up the other channels. The boats passed on the 22d, but, on account of drift-ice, nothing further could be done on the part of the dam, which now remains unfinished, but perfectly safe, as there is a foundation of two courses of fascines, securely anchored with stone and gravel.

PLAN OF CONSTRUCTING WING-DAMS.

The plan adopted required only the use of brush, with sufficient stone to retain the same in place, and the addition of gravel to prevent leaks under the brush. The brush was made in fascines of 10 feet long and 12 to 15 inches in diameter, securely bound. The fascines were then formed into mats of about 9 feet wide, by placing a number of fascines side by side, and placing light poles on top and bottom, and tying the ends of the poles with twine. Having determined the position of the dam with stakes driven into the sand, a sufficient number of mats were prepared as above stated, and a quantity of stone and sand-bags being in readiness, the work was commenced. While the weather was warm several of the men would get into the water to place the mats in position; afterward the same was done from scows and boats. The mats were floated into position and sunk by placing stone and sand-bags upon the same. They were placed side by side in the line of the dam, and the bottom row carried to the entire required distance; the brush-ends or tops were placed up stream, and after the first course was laid the tops were covered with a layer of gravel to prevent undermining, and the carrying up of the dam to the required height was proceeded with according to the depth of water; sometimes two or more courses were carried forward together, but upon approaching the surface it was found advantageous to carry the whole up uniformly, so as not to concentrate a rush of water to any one place; each course was brought forward from 2 to feet, in order to allow the next lower one to project out behind, upon which the falling water would impinge, and its force be broken.

After the dam was carried in the above-described manner a little above low water, a substantial layer of loose brush was placed along the entire face of the dam, and covered with a layer of stone, and then with sufficient gravel to stop all leaks. A cross-section of dams is shown on accompanying map.

To facilitate the work on the improvements, it was necessary to build one skiff and three scows.

The scows were built of pine. One is 45 feet long, 14 feet wide, and 22 inches high; the other two are 70 feet long, 17 feet wide, and 42 inches high. Both are provided with spuds, or growsers, and one was supplied with stern-wheel, steam-engine, and boiler, for the purpose of operating in shallow water, but was not completed in time to be put to work with safety, from the severity of the weather; the boat was allowed to make a trial trip, which was very satisfactory, and was then laid up.

A scraper, of which plans were submitted in October, was constructed and attached to one of the working-boats, and operated with much satisfaction; the boat was thereby enabled to make its way to any desired point without any difficulty.

The whole number of dams built is 22, ranging from 50 to 700 feet long; one is 1,200

feet long, but answers more as a longitudinal than a wing dam.

The following is an account of the expense of the work to December 1, 1871:
The total length of twenty-two dams is 6,621 feet.

Cost of labor and materials expended on construction of dams.

Cost of labor and materials expended in the construction of boats.

$11 25 8.40 78 74

6 84

105 23

$1,060 43 137 25 15 50

714 14

272 37

52 57 1, 128 35 53 26

Miscellaneous materials.

Cost of moving boats from Portage to Lone Rock, and of moving United States boats and property from Prairie du Chien to Lone Rock.

The general effect of dams was the usual effect of contractions; the water was elevated above the contracted part in some cases as much as six inches, but subsided again as the channel accommodated itself to the change.

In the case of cross-dams, a general movement of sand took place for some distance above, and to a considerable distance below the work; and as soon as the current was checked there was a deposit of sand in front of the dam in its whole length.

With wing-dams there was always a considerable increase in the velocity of the current, in one case carrying steamboat and barge over the end of the dam.

As soon as the dams were brought to the surface, there was a rapid deposit of sand above and below the same; the deposit above was concave, and that below convex to the axis of the stream.

In connection with the work, observations were made of the movements of sandbars, and the effect of the work upon the same. The movement at Portage was from 3 to 5 feet per day, and by comparison this appeared to be the average upon the river, unless disturbances took place. At Dekorra the effect of dams caused a movement of from 7 to 14 feet in twenty-four hours, and at Lone Rock from 6 to 20 feet in twentyfour hours.

The bars moved along at this rate until reaching the dams, and then receded as rapidly and disappeared, the sand being deposited behind the dams.

The general result of the work, as will be seen from the accompanying maps, is very good.

The least reliable water, on that portion of the river near the upper crossing, before the work was commenced was 2 feet, and after the work the latest survey shows the least to be 3.7 feet, practically 4 feet, and still improving.

On the improved portion, near middle crossing, where now the channel is, there was a dry sand-bar at least 1 foot above water; at the time of the last survey there were 4 feet, and improving.

There are of the two portions together about seven miles of river cleared of sand to a reliable depth of 4 feet, and with another dam opposite No. 5, above Dekorra, and the enlarging of Lone Rock draw, 5 feet could be probably relied upon. The work has thus cost about $4,000 per mile, including all expenses arising from the experimental character of the work, and much more so on account of the unusual low stage of water during the season, there having been neither the usual June nor September rise. From the result of the work it would appear that it is only necessary to contract the stream proportionate to the required depth, everything else depending upon the sta bility of the dams, of which I have not the slightest doubt, as I consider the test which they withstood when in that particular stage of progress, when the water poured over the same in an entire sheet, as much severer than any resulting from high water.

Concerning the stability of the channel produced, the question arose as to whether high water with increased pressure and velocity would not continue excavating the same until banks and dams would slide in, and the channel become useless; this gave rise to an examination of the river where the same is confined to a narrow channel, so that its depth is from 6 to 8 feet at low water; at such places the bottom is found to be composed of coarser material, and gives considerable resistance to the thrust of a pike; the bottom always remains the same excepting during the passage of a sand-bar during a freshet.

The following is a table of the weight of sand from different localities:

The last is usually found in digging wells in the vicinity. this report, numbered to correspond with the above table.

The table of weights shows that the density of the material increases downward. The results of the experiments and investigations have clearly determined the feasibility of improving the river-bed by means of dams at a comparatively moderate cost. From the expenses detailed in this report it will be found that from the expenses incurted in the actual work of constructing dams, including engineering and superintendence, the cost of dam has been $3.86 per linear foot; and although the same is moderate, yet it can be reduced very much, from the facility with which the work can now be done, as compared with the commencement, and the improvement which may be made in building dams, although the plan adopted appears to be the correct one. The following estimate is based upon 36 miles of river taken promiscuously at different portions of the same, and locating the dams in number and extent for a reliable four-foot navigation, but which may possibly turn out five.

In 36 miles of river the number and length are

Of cross-dams, 41, which equal..

Of wing-dams, 57, which equal..

Of shore protection, 31, which equal..

Giving a total length of dams equal to..

Which, at a cost of $3.50 per foot, equals.....

And gives an average per mile of..

And for the entire river, (say 110 miles)..

10, 682 linear feet. 15, 020 linear feet. 1,980 linear feet.

27, 682 linear feet. $96,887 00

2,691 30 296,043 00

I do not think that the actual cost will exceed this estimate, although some of the work will cost considerably more; other portions, again, can be made comparatively cheap; and as some of the dams require only to be built in two or three feet of water, I give an estimate below for a dam constructed of one large fascine, composed of brush on the outside and filled with sufficient stone or gravel to secure the same when placed in position.

The fascines will be three feet or more in diameter, and bound together with hoops. They can be built of any required length up to 70 feet, on scows, or on the river-bank, and afterward rolled upon the scows, which will be brought to the position of the dam and the fascines launched over the side. This idea was suggested to me by a gentleman who had been engaged as overseer on river-improvements in Germany, where the same was used to very great advantage; the same had also been used in stopping breaks in dams and levees.

The following is an estimate for 100 linear feet:

The above will answer in many places; and at others it will, with the addition of a course of brush and stone covering, costing, in addition, not to exceed $1.50 per foot, make a substantial dam at a cost of only $2.28 per linear foot.

It would be advisable during the coming season to confine the work to the worst places between Portage and Sauk City, a distance of 28 miles, and from Richland City to the mouth, a distance of 48 miles. The probability is that with the money yet available a reliable navigation can be made on those two portions to meet present requirements. The middle portion is obstructed with bridges, which require to be rebuilt before anything satisfactory can be done, and as soon as the work is sufficiently advanced the necessary steps should be taken to cause the removal of these obstructions.

A new railroad-bridge was built on the upper portion during the past season, and is rather an improvement on that portion of the river; the available width of waterway is 250 feet at low water, with a depth of 10 feet; there is one bay, of 132 feet in the clear, adjacent to the right bank, and then follow two draws of 59 feet each; the bottom of the truss is 27 feet above low water, and the roadway 45 feet.

As a final result of the improvement, if the supply of sand still continued, there would be a general elevating of the river-bed; the dams, at their original height, would no longer fulfill their purpose, and the river become as it had been before, and, perhaps, in many places, seek a new channel in the bottom-lands.

From the examination of the upper river, the source of the supply has become evident, and I estimate that about 4,500 feet of dams, at a cost of about $30,000, would stop almost the entire supply; this expense would seem considerable, but I think warrantable, since the ultimate results will certainly be as before stated; and, furthermore, a successful result of the work in hand, and a further development of this portion of the State, and consequent increase of business, could possibly call forth the idea of improving the upper river at no distant day.

I will conclude with a few remarks on the location and direction of dams. The approximate location of a dam is indicated by sand-bars or shoal water; but the precise location must be determined in connection with the desired results above and below for some distance.

The current, driven to the opposite shore by a dam, will most certainly return at some point below, since the dam will cause the surface to become lower on the side adjacent to and below the dam; the elevating of the water on the concave side of the stream will also induce the current to draw toward the same side above the dam, (to the adjacent side.) The above is the result of experiment, and in opposition to the idea of building a slanting dam on one bank to direct the channel to some point on the other, lower down. The best direction to give a dam is to locate the position of the head of the same, and then take the shortest line to the bank; the result is practically the same whether the line be up stream or down, or a normal to the bank. Respectfully submitted.

Colonel D. C. HOUSTON,

United States Corps of Engineers, Chicago, Illinois. PORTAGE, WISCONSIN, December 26, 1871.

JOHN NADER,

Assistant United States Engineer.

Report on an examination of the Wisconsin River from Grand Rapids to Portage City.

In accordance to verbal orders received October 1, 1871, relative to making an examination of the Upper Wisconsin River, I left Portage City October 3, with two men, and proceeded by wagon to Grand Rapids, arriving the morning of the 5th, and on the 6th started down the river in a skiff.

The Wisconsin River, for about eight miles below Grand Rapids, runs through a rocky region; the bed of the river is very rough and uneven; and bowlders of all sizes jut forth, rendering navigation exceedingly difficult. Attempts have been made, very successfully, to improve these rapids by building wing-dams from either shore toward each other, leaving a gap of from 70 to 80 feet, making water enough for rafts through it, and increasing the depth above. These dams are wooden cribs filled with stone. A number are new; four, on the Whitney Rapids, were built during the last season. An experiment upon the velocity of the water through one of these chutes gave a discharge of 200 cubic feet per second.

The rocks are hard, of igneous character, and without regular stratification. There is no sand whatever in the vicinity.

The character of the river-banks soon changes, the rocks gradually disappearing,