somewhat from its having been sunk under water, as stated in my reports Nos. 55 and 73, to the bureau, the first made on the 25th of November, 1854, and the other on the 29th of April, 1855. These repairs were made at the expense of the committee appointed by the delegates to act for them, and the dredging of the middle channel of the South Pass*-or that which had been adopted by the War Department under the recommendation of the Board of Engineers, and Topographical Bureau, as the one to be improved-was commenced the latter part of July, 1855. The work was conducted under the immediate supervision of Frank Williams, esq., civil engineer, of Buffalo, who had been selected by the committee of the delegates to make the examinations of the nature of the work, and the estimates for them. He acted under the general direction of this office, and in accordance with the instructions hereto attached, marked N 25.

The dredging was confined to the cutting of the channel, CD, (see map G, No. 34, herewith presented) sixty (60) feet wide, with the design of making it wider on completing the first cut, from 12 feet depth in the lake to the same depth in St. Clair river. The depth of cutting was set at thirteen (13) feet in order to allow something for a slight filling up from the wash of the lake waves, should such take place.

The dredging was much interrupted by the unusually stormy nature of the season, which has so often been adverted to in preceding parts of this report, when treating of the operations at other harbors. From this cause no work of any consequence was done after the termination of the first week of October, although the dredging machine remained in position for work until the 28th day of that month.* The result was, that nineteen thousand five hundred and eighty-nine (19,589) cubic yards of soil were excavated and removed from the proposed channel-way. Although the extent of the improvement, thus produced, was not so great as had been anticipated before the work was begun, yet even this effect was of an appreciable benefit to commerce, because it gave a narrow channel carrying nearly ten feet through it, and over the flats, from deeper water in the lake to deeper in St. Clair river. Should it be found on the opening of spring not to have been injured by the wash of the lake waves since the dredging was discontinued, it will be quite practicable during the season of 1856 to give a narrow channel, twelve feet deep, clear over these "flats," provided the necessary funds are granted by an early appropriation for that object. Such an effect would be hailed as an important era to the commerce of the great lakes.

The nature of the soil to be removed has proved to be more tenacious and more difficult than has heretofore been estimated. Instead of being light sand throughout, to a depth of twelve feet, Mr. Williams reports it "to be of two kinds, viz: on the surface, and to a depth of two to three feet we find (he says) a clear, coarse sand; be low this, there is a deposite of sand and clay, very firm, so that it requires the whole working force of the engine to drive the bucket int it." (See report, marked N 26, hereto attached.)

*See map G, No. 33, herewith submitted.

See reports marked N 29, N 31, and N 32, hereto attached.

From this experiment I am compelled to increase the estimate for the necessary dredging, in continuation of this improvement, from twelve and a half cents per cubic yard to double that rate.

Mr. Williams informed me that the dredging already done cost at the rate of thirty cents per cubic yard.

The expense of the preliminary preparations, and the stormy nature of the season often interrupting the work, probably enhanced the cost somewhat beyond what it would be in future. I therefore put it in the accompanying estimate, marked N 35, at the rate of twenty-five (25) cents per cubic yard. The number of cubic yards, yet to be excavated is 110,133.

This estimate calls for an appropriation for excavating a channel 300 feet wide and 12 feet deep through the middle approach to the South Pass, including the necessary appliances and the requisite repairs of the dredging machine before commencing the work, of $46,159 07; that is to say, forty-six thousand, one hundred and fiftynine dollars and seven cents.

The bureau is aware that there is no balance existing applicable to this work, or to contingent expenses relating to it. The above estimate is confined to the last approved plan, (see Docs. N 9 and N 10 hereto attached,) which is limited to dredging only, as the first work to be executed.

I must, however, remark, that I think the opinion of Colonel Abert, chief topographical engineer, expressed in his letter to the War Department of September 30, 1854, in regard to this improvement, is well founded, and ought to prevail, namely:* that it will be necessary to protect the artificial or dredged channel-way by appropriate defensive works, in order to prevent its being filled by deposites of sand that will otherwise be carried into it by the action of the lake waves in rough weather. The report of the board of engineers, as I understand it, does not positively reject all protection of the artificial channel-way, but it rather proposes, as a measure of proper economy, to defer it until it shall be shown by experience to be requisite.

Viewing this point as the most important to be investigated in the earliest stage of the improvement, I gave to it all the attention that was in my power to bestow in November last.

While we must admit the justice of the view taken by the board, that it would savor of extravagance to erect these protecting works, provided they can be dispensed with, yet, on the other hand, it should be borne in mind that to open the proposed channel-way will of itself be a costly operation, and unless we guard it as we progress, we may lose its benefits to commerce entirely, together with the money it will have cost. I would therefore respectfully suggest that this point should be regarded as the preliminary first of all to be settled.

On the 13th November ultimo, aided by Captain J. N. Macomb, of the corps of topographical engineers, who very kindly took part in the operation, and furnished the boats and crew belonging to his equipment for the survey of the lakes, I made a close examination and survey of the state of the channel which had been cut out by

See a copy of this letter, hereto attached, marked N 8.

dredging, between the last of July and the last of October previous. The depth to which it was originally cut, as reported by Mr. Williams, was thirteen (13) feet.

The result of the soundings taken by Captain Macomb and myself, on the 13th of November, is shown on the accompanying map marked G No. 35. It will there be seen that the depth of a portion of the dredged channel had diminished as much as one and a half to two feet, and that the average diminution throughout was one foot within an average period of thirty-seven days, deducting the portion of October in which no dredging was done.

This diminution was, no doubt, caused by the action of the lake waves on the sandy bottom during the strong gales of wind which prevailed to so great a degree throughout the past summer and autumn. The result indicated by the survey is sufficient, I think, to show the necessity of protecting the artificial channel-way by works of a permanent character, capable of resisting, for an indefinite period, the action of the lake sea. Although this action is not so forcible as upon the great lakes, yet it is one of almost perpetual duration. The sea has here a sweep of eighteen miles throughout four points of the compass, namely: from southeast to south, and of about sixteen miles throughout four points more, namely: from south to southwest. It is true the protecting works will be in shoal water, and close piling of oak timber one foot square, driven at least twelve feet into the soil at bottom, might resist the force of the lake sea in ordinary seasons, and the drifting ice in winter for two or three years; yet there would be but little dependence to be placed upon a structure of this sort for a longer period. The channel, being once opened by dredging, should not be subjected to the vicissitude of being closed or interrupted by breaks in its defences. The immense commerce and navigation looking to a safe outlet here should not be exposed to the probable chances of such disasters.

After having given every attention in my power to the subject, I have respectfully to represent that I do not think the artificial channel, when opened by dredging, can be made secure without the protec tion of two parallel piers constructed, one on either side of it, in the usual way. I therefore recommend this as the character of the improvement to be adopted. These piers would have a total length of 7,880 feet-that is to say, the pier on the northwest side (see the line A E on map G No. 35) would be 3,880 feet long, and the pier on the opposite or southeast side would be 4,000 feet long. It is recommended that the cribs to form this pier-work should be each twenty feet wide. and seventeen feet high from bottom to the flooring at top, thus making the flooring five feet above the water surface, and that they be constructed in conformity with the drawings given on the accompany ing sheet marked G No. 19, except in regard to the bolting, which should be of round wrought iron one and a half inch in diameter and arranged as is shown in sheet G No. 21.

The cut-out channel thus protected would tend to prolong the cur rent from St. Clair river with sufficient velocity to aid greatly in keeping it open.

If it were practicable to perfect the defence of this channel within

a reasonable time by the pier work alone, it would be the more economical plan to do so, and to dispense with close piling altogether. But, considering the amount of work necessary to be accomplished in building the piers, it would occupy at least five and a half years,* with all the activity that could be used during the working seasons.

The immense amount of commerce before alluded to, and which is shown by the accompanying statistics to be dependent upon this channel for its prosperity, ought not to be subjected to so long a delay in securing its practical benefits.

The States of New York, Pennsylvania, Ohio, Michigan, Indiana, Illinois, and Wisconsin, and the territory of Minnesota, have their shores washed by the great inland seas, whose intercommunication, by ship navigation, is much interrupted by the want of a safe and sure channel over these flats.

The States of New York, Pennsylvania, Ohio, and a portion of Michigan, on the one side, are crippled in their important commercial relations with the remaining portion of the State of Michigan, and with the States of Indiana, Illinois, and Wisconsin, and the territory of Minnesota, on the other side, by this intervening obstacle. Something would seem, then, under the purview of the Constitution, to be necessary to be done, in order to regulate the commerce between these States. Viewed in this light, the subject becomes one of great public

concern.

The value of the articles of commerce and navigation which passed over these flats during the two hundred and thirty days of open navigation, in the year 1855, say between the middle of April and the 1st of December, will be presently shown to have amounted to the immense sum of $259,721,455 50; that is to say, two hundred and fifty-nine millions seven hundred and twenty-one thousand four hundred and fifty-five dollars and fifty cents. Or, per day, during the navigable season, $1,129,223 72. The improvement, then, when undertaken, should be executed with a degree of permanency and celerity combined, commensurate with its importance and the magnitude of the interests involved.

To accomplish these ends, I would respectfully recommend that the dredging be commenced without delay, and be pushed forward with all possible energy; that close piling be commenced at the same time and pushed forward on the line B F, (see map G No. 35,) so as to afford a temporary protection to that channel as fast as the latter shall progress. In this way a narrow channel of 12 feet in depth, capable of letting the largest class of vessels through, would be opened the first season, together with aprotection on the southeast or windward side, that would prove efficient for at least two and a half or three years.

At the same time, the northwest or leward pier should be com

*This would be at the rate of 44 to 45 cribs finished and sunk in position in each working season, which is a very large allowance.

It is not meant by this expression that southeast winds are more prevalent, or that they blow with more force than northeast or northerly winds, but that the effect of southeast winds will be greater upon the work because they have a greater sweep over the lake, while those from the northeast and north are sheltered by the land.

menced and extended on the line A E, (map G No. 35) or perhaps on a line parallel with it and 100 feet more towards the northwest. To complete this pier would occupy 2 years. At the end of this period the dredging will have attained a width of 300 feet, with a uniform depth of twelve feet, which is allowing forty thousand cubic yards, as the quantity of this tenacious mixture of sand and stiff soil, that could be excavated in a single season by the use of the single dredging machine now belonging to this work.

Immediately on the completion of the northwest pier, the opposite or southeast pier should be commenced on its appropriate line, for it will then have been decided whether the channel should be limited to a width of 300 feet, or be wider. If 300 feet be fixed on as the limit, the southeast pier will occupy the line of the piling B F, (map G No. 35.)

If a greater width shall be decided on, that pier will be placed so much further to the southeast, and parallel with that line. The piling will, in the latter event, be then removed by either drawing the piles, or cutting them off with a proper machine, even with the bottom of the channel-way.

If this plan were carried out, the following result might be relied on, namely:

1. A channel-way 100 feet wide (considering the dredging already done) and 12 feet deep, capable of letting through the largest class of vessels, together with the close piling on the windward side, and about forty-four cribs, say 1,408 feet in length of the pier on the northwest side, would be accomplished the first season.

2. At the end of the second season 44 additional cribs would be attached to the northwest pier, making its length 2,816 feet, and the 12 feet channel would be widened to 200 feet.

3. During the third season the northwest pier would be finished by adding 33 cribs, (29 of which would be each 32 feet long, and the remaining 4 would be each 34 feet long,) and the 12 feet channel would be increased to a width of 300 feet. Besides which, 11 cribs would be built and placed on the line of the southeast pier, giving it a length of 352 feet.

4. During the fourth season 44 cribs would be added to the southeast pier, making it 1,760 feet long, and the 12 feet channel would be widened to 400 feet, if required, by the conditions of the approved plan.

5. At the end of the fifth season the southeast pier would, by the addition of 45 cribs, have a length of 3,200 feet, and the 12 feet channel would, if required, have a width of 500 feet.

6. By the middle of the sixth season the southeast pier would be finished to its required length of 4,000 feet, and at the end of that season the full width of 600 feet of channel-way would be accomplished, having a uniform depth of 12 feet.

The only difference in cost between a width of 300 and 600 feet for the channel-way would be $27,533 25, arising from the double quantity of dredging. (See the concluding remarks in estimate N 35.)

I would respectfully suggest that more exact information than we now possess should be obtained respecting the probable ratio of in