The borings into the soil of the yard, to the depth of 77 feet, exhibit the prevalence of this deposite of alluvial, with an occasional mixture of gravel, and a stratum of quicksand. This quicksand is composed of very fine sand, with little or no foreign mixture. It is formed by water coming from a higher source than the stratum, and, filling and enlarging the voids in the sand by, hydrostatic pressure, prevents the compactness due to solidity.

The alluvial of the Mississippi is susceptible of compactness, hardness and solidness to a certain degree, in the process of being made perfectly dry, and it will then stand with its surface cut vertically; but when it is saturated with water, it becomes semi-fluid, with increased weight equal to the weight of water filling the void, which by experiment was found to be in proportion to the dry alluvial as 1 to 3.5, whilst the bulk of water to that of the alluvial was as 1 to 3.75,

By this it appears that the soil formed from ordinary alluvial deposites is susceptible of great compression, and is thus unfit in its natural condition for foundations intended to sustain heavy weights, either by constant action or by percussion.

2. The mouth of Wolf river has been projected twenty-seven hundred feet from its mouth near the bluff into the Mississippi river, during the last twenty-five years.

The changes of the current from direct action on the bank at and above this point, to a line running nearly parallel to both banks of the river, has found an eddy current in which the work of deposite has been carried on. The accompanying eye sketch exhibits the river at and above Memphis. The dotted red lines and arrows show the old channel and the direction of the current against the eastern shore. The dotted black lines and arrows show the direction of the current as it now runs.

If the current continues in its present direction, there is little danger of the river making inroads upon the sill of the navy yard. If the point at Y continues to wear away, as it has been slowly doing for several years, the river will evidently become straighter, and its current will be less injurious to the banks on either side. The island X, however, is being slowly washed away. The effect of its dissolution would perhaps draw the current over to the old channel, and show it again towards Wolf river, tending to remove the present deposites at its mouth.

The currents of alluvial rivers offer a problem yet to be solved, whilst the direct current is the cause of abrasion of the banks at points where its action is unobstructed, and the reverse or eddy current the cause of the deposites forming new banks; the cause of the change, often sudden and capricious, of these currents, is not yet ascertained. These changes are constantly taking place, and it is doubtful, if the laws that governed them were known, whether they could be ever brought under control by works of art. 3. We can offer nothing on this point from any stock of information obtained from actual observation. A year would be the least time necessary to be devoted to the work. We can at present only refer to the report, by acting master Marr, U. S. N., of the observation made by him on the Mississippi river opposite the navy yard, during the year ending on the 1st March, 1851, and to a diagram of said observations.

In making the reference, we would commend the fidelity and ability with which it appears the work was performed by Mr. Marr.

By this report it is seen that the mean rapidity of the surface current is 2.41 miles per bour; the rapidest current being in May, 1850, and the slow

est in November, 1850; the former being in 4.31 miles per hour, and the latter 1.87 mile per hour; and that the order of months for the rapidity of mean currents was, May, 4.31 miles; March, 4.15 miles; April, 3.96 miles; February, 1851, 3.6 miles; December, 3 miles; July, 2.8 miles; June, 2.65 miles; August, 2.62 miles; January, 1851, 2.44 miles; September, 2.42 miles; November, 1.87 mile; October, 1.79 mile. Again it is seen that the highest rise of the river was in May, 1850, and the lowest fall was in November and October, 1850, at which time the level was thirty-one feet below the highest point in May. Thirty-seven feet below this point, is generally considered as extreme low water. The order of months for rise and fall of river,-May, March, April, February, 1851; December, January, 1851; June, July, August, September, October, November.

4. Observations extending through one year would be necessary to afford the desired information on this point. It is very difficult to learn from the inhabitants what the deposite or wash has been at different points. In perfectly still water, confined by embankments, the deposites differ both in quantity and combination of the materials from that made when the water is in motion, and overflowing the banks. In the latter case the sand in the alluvion is mostly deposited first, whilst the clay and vegetable matter sinks by degrees further from the shore. It is suggested, that, previously to the next rise in the river, that portion of the site remaining in its natural state and subject to overflow should be carefully levelled and referred to a bench mark; and that after each overflow, levels should be taken within the year. By this method the natural deposites would be accurately ascertained. The wash of the banks at different points must also be obtained by measurements. 5. The commissioners think that the river front cannot be secured against the action of the current, by any permanent works, and are therefore not prepared to offer any plan for the same. Rafts of logs, and wharf boats, lying along the banks, tending to be increased by deposites, aid in the formation by enlarging the reverse current. But the increase as well as the decrease of the banks militates against permanent works, being destructive of them or of their utility. No permanent works attempted to be constructed for the security of the river front, at any point on the Mississippi exposed to the full force of the current, has ever been successful.

6. For the reason that the river front cannot be secured against the current, no permanent dock, wet or dry, could be conveniently constructed; or if constructed, could be preserved from the intrusion of the current, or from deposites being formed in front, either action tending to destroy the efficiency or endangering the safety of the dock. A floating dock would, under all circumstances, be best adapted to this locality.

7. Building-slips could not be readily or securely constructed, being subject to the same causes of destruction as the permanent dock is. It is very doubtful if a ship of considerable size could be launched with safety from the banks of the Mississippi at this point. It would be very difficult to construct the launching ways upon a sufficiently solid foundation. Any giving way of these foundations at the time of launching would do great injury to the ship.

8. We think that the best, and of course the most economical method of constructing the foundations on the present site, would be as follows: The excavations should be carried down deep enough to obtain constant moisture, in order to the preservation of timber. At this depth, a grillage of timber should be laid, by first placing a larger parallel, with the intended

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wall to be supported, the cross-section of the pieces of timber being a rightangled-triangle, with the hypothenuse turned upwards and level. Three lines in this layer should be thus placed, one foot or fifteen inches apart, and forced into the ground by several laps of the pile driver: cross-pieces should then be laid over the first layer one foot or fifteen inches apart, the intervals varying with the size of the piles to be afterwards driven. Piles are thus driven in the intervals of the grillage, with the force demanded by the nature of the structure to be supported. In this case there would be two rows of piles. The timber of the first layer is made in the form of a triangular prism for the purpose of increasing the under surface of resistance which the two sides afford. Joints are carefully broken throughout the first layer of timber. The piles are cut off even with the surface of the upper layer, I and concrete is filled in the intervals when the superstructure is commenced. I (See sketch.)

9. With the exception of the sandstone used in the construction of foundations of the buildings for offices, rope factory, commandant's house, joiners' shop, lime-house, tarring-house, terrace and yard walls, and also in the blacksmiths' shop, saw-mill and storehouse, which are not completed, the materials used in construction generally appear to be of good quality, and suitable for the purposes to which they have been applied. The limestone which will be used in the foundations of the hemp-house, is of superior quality. The sandstone is not of a quality suitable to solid construction. Its unfitness is particularly exhibited in the terrace wall, where some blocks of it have been scaled by the sliding tendency of the wall.

10. The examination of the records of piling of foundations in the different buildings, shows that the work was imperfectly done, and that the foundations are not as secure as it is desired they should be, with the exception of those of the lime-house and the hemp-house, now under construction.

Several cracks in the walls, evidently due to the subsidence of the foundations, are discovered. These indeed do not threaten serious injury to the buildings, and, from the length of time the foundations have sustained their present weights, hopes are entertained that little or no more subsidence will take place, except in the case of the foundations of the saw-mill. The unequal settling of this work is so great as to render the abandonment of the site necessary. Fortunately no necessity exists, at least at the present time, for the completion of the superstructure.

The maximum of settling in the buildings already completed, is exhibited in the one intended for offices. The greatest motion appears at the N. W. and S. E. angies, where the pillars of the piazza rest, but all four of these angles are more or less affected. This motion is due as much to the thrust and weight of the arches which are thrown between the foundation piers of the pillars, as to general subsidence. The two arches adjacent to each angle pillar, tend to throw these pillars out of a vertical position, and at the same time impose double the weight on their foundation piers and piles, of that sustained by any intermediate pier. We were at first at a loss to understand the object in constructing these arches, and as their injurious effect upon the stability of the building was very apparent, we thought it best that the crown of the arch should be broken through. But on reflection, after learning that the piles supporting the pier foundations of the pillars were not driven at the exact distances at which these pillars were to rest, and that they differed considerably in this respect, it was concluded that the

object of these arches was to afford a foundation upon which the position of the pillars could be marked out at equal distances, without regard to the piling underneath, and it was therefore determined not to cut through the arches as at first proposed. Still some security against the lateral pressure produced by the thrust of the arches is required, and we recommend that bands of iron, one inch square, should be curved round the building just below the water-table, and tightened with screws.

The wall supporting the upper terrace, upon which the commandant's house is situated, has given out, and as the motion is undoubtedly in progress, threatening the final overthrow of the structure, additional support to the pressure of earth becomes necessary. The reparation may be accomplished in either of these ways: 1st. By taking down the defective portions of the wall and rebuilding them. 2d. By removing the earth from the back of the wall and sinking wells and counterforts. 3d. By erecting two sets of stone stair-ways and four buttresses along the face of the wall. The last of these methods will be the least costly, can be more readily carried into effect, and at the same time will combine utility with the additional strength required, the stone stair-ways affording more easy communications with the lower terrace, and additional support as buttresses to the wall. The dimensions of this wall, twenty feet above the foundation, nine feet at base, and four feet at top, were probably calculated to sustain earth standing wet or dry at an angle of 45°. From the nature of the soil, becoming semifluid when saturated with water, the dimensions should have been increased so as to be nearly equal to those due to the pressure of water. In digging down the bluff, care should have been had in forming steps in the natural earth, and ramming the earth filled in between the wall and these steps.The failure to use cement in the mortar and in construction, is another fact unfavorable to stability. At all events, bad materials and workmanship, added to insufficient dimensions, renders it necessary that timely reparation should be made.

With the exception of the building intended for offices, and the headhouse of rope factory, the buildings of the yard appear to be well planned, and adapted to the uses for which they were intended. The first named building is faulty on account of the massive pillars and entablature by which it is surrounded. The nature of the soil makes it desirable that all unnecessary weight in building should be avoided.

Besides, the entablature descends so low as to mask the windows of the upper story and exclude the light in a considerable degree. A light piazza could have been constructed on iron columns, affording equal advantages with the present structure, and exhibiting better taste. The only objection to the plan of the head-house relates to the thickness of the walls, and the span of some of the rooms being left without sufficient support. The walls are only twenty-two inches in the lower, and eighteen inches in the upper story. They should have had an average width of two and a half feet.— Great solidity in the walls of this building is required, in order to sustain the weight of roof, floors and machinery, and to resist the shock of the machinery when it is in full effect. The beams supporting the floor of the room in which the machinery for dressing hemp is placed, are thirty-five feet long. This span is too great; and though these beams are 15" deep by 5′′ wide, the motion produced under the operation of only two machines is very perceptible. It is proposed to stiffen and strengthen some of these

neams and connect them with the walls, as shown in the sketch marked 2, attached to this report.

It should be here remarked that we entertain one objection to all the buildings, relating to plan and construction, on account of these not being made fire-proof. We think that all buildings connected with the great public establishment of the country should be made fire-proof, and there are none more exposed to danger from this element than those in navy yards, where large quantities of combustible materials are necessarily collected.

The sites of the respective buildings are well selected with the exception of that for the building for offices. Its location nearer to the main gate, and on the upper terrace, would, it is thought, have been more convenient for the transaction of business with the several offices; but if it be applied to the purposes recommended, its location is well enough.

The workmanship is generally good, but we except the framing of the roof of the rope factory. Much of the defect is undoubtedly owing to the use of unseasoned timber, but still there is bad workmanship exhibited. The brick masonry generally might have been made better, by carefully wetting the bricks before use, and mixing a due proportion of hydraulic cement with the mortar; we recommend the use of cement mortar and wet bricks in the construction of the other buildings.

11. Temporary wharves may be constructed on piles driven into the bank of the river. These wharves would afford facility for landing at the high and mean stages of the river; but at the low stage, their height above the level of the river would for the most part destroy their utility. floating wharf would be best adapted to the locality.

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Besides, the cause operating against the securing of the river front by permanent works, would also prevent the erection of permanent wharves.

12. The facilities of embanking and filling up the yard to a proper level, are considerably diminished on account of the distance from which earth may now be obtained. A cubic yard of earth placed in the area on the eastern side of Wolf river, would now, probably, cost fifty cents. The space remaining to be filled up, according to the original grade of the yard, and after the present contract for filling up is completed, we estimate approximately to be equal to 450,000 cubic yards. To the amount of required embankment, there should be added at least 12 per cent. for compression of the earth. We think the quantity thus obtained will be near the truth; and assuming it to be so, we have

450,000 cubic yards of space to be filled

56,250 do. =121 per cent. for compression of embankment.

506,250 do. at 50 cents per cubic yard, $253,125.

This would be the probable cost for completing the embankments on the eastern or southern side of Wolf river to a proper grade.

The original estimate for the embankment on the opposite side of Wolf river, makes the space to be filled up equal to 622,400 cubic yards.

622,400 cubic yards.

12 per cent. for compression of embankment.

do. at 50 cents, is $351,075.

This would be the probable cost of completing the embankment on the