rents and costing far less than a harbor of like dimensions made of stone piers. Although I am relieved from duty here, it is at the request of Lieut. Col. Henry M. Robert, Corps of Engineers, my successor, that I forward this project, as the studies for its plans, &c., were made under my direc tious by Mr. Stierle. Very respectfully, your obedient servant, W. H. HEUER, Major of Engineers. (Through Lieut. Col. W. P. Craighill, Corps of Engineers, U. S. A.) REPORT OF MR. A. STIERLE, ASSISTANT ENGINEER. UNITED STATES ENGINEER OFFICE, SIR: I have the honor to submit herewith plans and estimate for an ice-harbor at the head of Delaware Bay, in conformity with the order of the Chief of Engineers, United States Army, dated Washington, D. C., February 15, 1883. This report is accompanied by two drawings; one shows the general plan of the harbor; the other is a detailed illustration of the inclosing works at their most complicated point—i. near the entrance. The results of an examination for a site for the proposed harbor were fully set forth in the report which I had the honor to submit to you under date of June 12, 1884, and which is printed in the Annual Report of the Chief of Engineers, United States Army. pages 817, 825. The proposition made therein to locate the harbor near Liston's Point having received your concurrence, the plans here with submitted have been especially designed for that locality, and are based upon data obtained by the preliminary examination. As the examination extended over a very large area, the data relating to the precise depth of the hard bottom substratum at the proposed site for the barber are particularly meager and need verification. The slope and the height of the piers, as as shown on the accompanying profile, are therefore conditional. The inclosure of the harbor is formed on the up and down stream side by curved iron barriers on the base, which is about 1,950 feet distant from the shore, and nearly parallel to it, by a row of clusters of wooden piles. At the outermost point is an opening left for an entrance 357 feet wide. The barriers form in plan an are struck from five centers, and approach is their curvature the perimeter of an ellipse, having a major axis of 2,400 feet and a minor axis of 2,000 feet. The length of the base is 1,950 feet. The length of one barrier, as drawn and to be constructed, is 1,840 feet. The combined length of both bar riers, adding the width of the entrance and calculating it circumferentially, from the north end to the south end of the base, is 4,037 feet, the whole inclosing an area of about 56 acres. Of this area 20 acres have a depth of over 24 feet at mean low tide The remaining area gradually shoals to a minimum depth of 5 feet. While it would have been more desirable to throw the harbor farther out into the river, mainly te obtain a greater and more uniform depth, the steep inclination towards mid-river of the hard bottom substratum upon which the structure rests confines the execution of the project within certain limits on account of the disproportionate increase in co structive difficulties and expenses. The area inclosed appears at the first glance to be larger than is necessary. When, however, it is considered that the available space containing greater depth than 24 feet of water is only 35 per cent, of the whole inclosure, which should as much as possible be reserved for the largest class of vessels, leaving the remaining area for the smaller and more numerous class of vessels, the size of the harbor is none too large. In my former report I have called attention te the many advantages which a curvilinear form for the plan of the harbor would give in the present case; first, by inclosing a larger protected area in proportion to the length of the barriers than if projected straight off shore, leaving only a narrow but sufficiently wide entrance, admitting but little ice during slack water and the preva lence of strong easterly winds; second, by being better adapted to withstand any pressure from the outside; and third, by preventing the ice from packing against it in large masses, thus compelling it to float on and out into the river. Although it is not impossible with a little care and skill to construct the axis of the barriers exactly along the line of the arcs as shown in the plan, it may suffice to place only the piers upon this line and to make the intermediary portions straight. The inclosure will then practically represent a polygon with sides 92 feet long. Along the base of the inclosure it is proposed to place a cluster of oak piles 50 feet apart, each cluster to be composed of three piles, to prevent ice-floes from entering the harbor from the rear. As the water is shallow and the line of the base is nearly parallel to the currents, whose strength is much reduced along the shore, it is not expected that these piles will have to sustain any undue pressure. As stated above, the barriers on the up and down river sides of the harbor are proposed to be constructed wholly of iron. A sketch of a portion near the outer end is shown on Sheet No. 2. This portion was specially selected for illustration of the details because it is more complicated and heavier in construction than the portions near the shore will be. As a supplement to the drawings a general description of the whole structure is herewith added. Each barrier is composed of a series of piers, placed 92 feet apart from center to center, connected together longitudinally by sections of less massively built bridge-work. The longest axis of the pier is placed normal to the curvature of the inclosure. Whilst the piers form the buttresses, the ice-breakers, in fact the foundations of the work, the sections connecting them, though lighter in appearance, are nevertheless calculated to withstand the pressure and shocks from the ice as well and as effectually as the former. Both barriers are protected on their convex sides with an iron-fender system, reaching to 11 feet below the plane of mean low water. The piers, the bridge portion, and the fender system, these constitute the three distinct and characteristic features of the structure. Each pier forms an irregular six-sided pyramid, composed of six hollow cast-iron columns 12 inches in diameter in the piers nearest the shore, increasing, as the height may require, to 18 inches in the piers farthest out. The pyramids formed by those columns will have a uniform height of 22 feet from Pier Nos. 16 to 21 of the north barrier, and from Nos. 10 to 21 of the south barrier; those inshore of the numbers named will be of less height, and will, as nearly as possible, follow the profile of the gravel substratum. surface area. The six piles of each pier are rigidly braced together by two series of horizontal struts, and longitudinally and transversely by vertical diagonal braces. The connections are everywhere to be made with round pins except in those cases where screwbolts are absolutely necessary. In fact, all the members of the substructure are designed plain and compact in cross-section, with as few component parts as possible, in order to present to the deteriorating influences of corrosion the least amount of It is proposed to "set up" each pier on shore and to float it into position subsequently with the aid of large pontons. The top stratum of the river-bed being very soft it is expected that they will sink into it for a certain depth; in the case of one of the outer, the largest piers, probably as much as 12 feet. The bearing capacity of this stratum will have to be determined by experimental tests. The bottom, notwithstanding its softness, will take up a portion of the weight of the pier. The lower end of each column is therefore in addition, to aid this purpose, extended into a horizontal disk of large diameter, which form bed plates with considerable bearing surface. Besides these disks the lower horizontal struts of each pyramid also offer additional bearing surface. It is obvious that in the same degree the weight of the mud superimposed upon these disks and other parts buried in the bottom will contribute materially to the stability of the piers. To fully secure them, however, and to prevent all possibility of their being overturned by external forces, the pyramids of each pier, as formed by the hollow cast-iron columns, are made to rest upon wrought-iron screw-piles of proportionate strength, projecting at the lower end from the interior of the columns and extending down to the substratum of gravel and stones, into which they are screwed. Before each pyramid is lowered, these screw-piles are pushed up as far as the screw below will permit, and are temporarily held within the columns until the accurate position of the pier is determined, after which they are fully and permanently screwed down into the gravel. The latter operation can be performed through the interior of the columns with a false socket and shaft fitting over the hexagonal or square head of the pile and subsequently withdrawn. To prevent any possible future movement or slipping of the columns upon the piles below, and to further secure them, set-screws enter the sides of the columns a little above the bottom of the river and fit into a corresponding groove or neck upon the wrought-iron piles. These screws are to be tightened by a diver, which will constitute the only diving work upon the piers. The cast-iron columns of each pier are to be filled subsequently with Portland cement concrete. The line of the inclosure between the piers is composed of a narrow bridge portion, standing upon six crossrows, of two each, of solid wrought-iron screw-piles. The piles have an inclination towards the axis of the barrier of 1 in 6, and extend to hard bottom from piers No. 1 to 16 in the north barrier and from piers No. 1 to 10 in the south barrier. From thence to the ends they are screwed into the mud to a general depth of 12 feet, with screws much enlarged in diameter, to afford greater holding power. Transversely and longitudinally the piles of the bridge portion are also, like the piers, connected together by sets of braces of suitable shape and dimensions, the points of connection at their upper ends being made to the caps of the piles, and at the lower ends to collars clamped around the pile and to corresponding lugs cast upon the sides of the adjoining columns of each pier. At the height of 8 feet above mean low water the superstructure of the barriers is laid directly upon the caps of the piles. This consists mainly of two U-shaped longtudinal string pieces or beams, & feet apart, between which smaller 1-shaped crossbeams are riveted over each row of piles, the whole being rigidly tied together by a series of horizontal diagonal braces. Within the intervals of the cross-beams, and 3 feet from each other, yellow-pine sleepers are interposed, upon which are spiked the planks of the decking, that forms a continuous gangway from end to end of the barrier. With its base bolted to the caps of the center pile and projecting above the decking a cast-iron mooring-head is provided for each pier, affording, with the ntmerous mooring-buoys which it is proposed to distribute over the interior of the har bor, ample facilities for mooring purposes. The fender system, which is nothing else than a grillage hung over the convex sce of both barriers, consists of four longitudinal | beams, about 6 feet apart, upon the ter of which are riveted crosswise a series of iron rails, leaving an open space betweek them of not more than 3 feet. The lower beams of this grillage rest upon the col· lars clamped around the piles of the bridge portion. The two in the middle are be to the same piles by wrought-iron clips, and the upper one rests in a corresponding recess or shoulder cast upon the outside of the caps, and is there additionally secures by lap-plates. The ends of the beams, extending slightly over the columns of the piers, are fixed by a similar arrangement. As seen by the accompanying drawing, the fender system is made to follow the pro jection created at the side of the barrier by the end piles of each pier. In this wat an acute angle is formed at that point, which, fortified with a sharp and broad ster plate fastened upon the fenders, acts as an ice-breaker, upon which the floating cak of ice will partly mount after striking it, since the cutting-edge has considerable clination, and before they have time to descend are likely to be broken in two by ther own momentum. No difficulty is anticipated in constructing the fender system in panels, in putting the latter together on shore, and in lowering them over the siles of the barriers into place as the work progresses. The depth below mean low wat to which the fenders should extend is at present not definitely determined. It is et thought, however, that the cakes and fields of ice, after striking the barriers an the influence of a strong current, will pile upon and sink each other to such a depth as is indicated in the drawing, viz, 11 feet. Practical experience and observatie must in this case, as in other points of like nature in this work, finally determine the limit as to depth to which the fenders against ice may be safely and economically carried. The general method to be followed in the execution of the described project word be to erect both barriers simultaneously, beginning at Pier No. 1. The piers, as state before, are put together on shore, and when placed in position simply secured with screw-piles. The intermediary portions of the structure would be constructed direc?}; at the place, as the work progresses, from a movable platform. How necessary it will be to complete in one season, or as rapidly as possible, a structure like this, which is weak in parts yet strong as a whole, will be apparent 74 any one who has observed the destructive effects of moving ice. The work shoutherefore, not be commenced until the full amount of money needed for its construe tion is available. The general estimate herewith submitted is based upon the a companying drawings, allowing for a reduction in dimensions wherever they are ta take place, and upon data collected from personal observation at a work similar in character-the United States Landing Pier in the Delaware Breakwater Harbor The estimate is considered a liberal one, and will certainly cover the total experS necessary to build an ice-harbor near Liston's Point of the extent, form, and character as herein described. The total cost of the harbor, as proposed, is estimated at $308,80% or at the rate of $83.91 per linear foot, or $5,514.28 per acre of projected area. These figures include 10 per cent, contingencies. At your request I have made a comparison between the cost of stone piers, heretofore used as protective works for ice-harbors, and the cost of iron piers like those of the proposed plan, and find that the averag cost of hexagonal crib piers capped with a stone superstructure built in Marens Hens and New Castle harbors has been about $20,000. The cost of the masonry in these piers has been nearly the same in all, as in each case it extends to about low-water level only. For a pier having an average length of 60 feet, an average width of 2 feet, and a height of 48 feet, the cost of one cubic foot of masonry has been 43 cents. or for each vertical foot $833. The cost of the crib foundation has been 11. cents per cubic foot, or $250 per vertical foot. The average height of the iron piers pro posed for Liston's Point Harbor is 44 feet, and the cost per pier, as estimated, is $3,363, or, including 20 per cent. contingencies (round $4,000), only 20 per cent. of the cost of a stone pier of equal height. Assuming that the iron piers of the plan submitted, which are 92 feet distant from each other, should be replaced by stone piers, their total cost at the above rate would be $777,000, or, if they were placed 100 feet apart-the distance adopted for the ice-harbor at Marcus Hook-$703,000. Although stone piers, when compared with iron piers and when properly built, are unquestionably of greater durability, stability, and weight-three important factors in the construction of ice-harbors-these favorable qualities are entirely offset by the tendency of the piers to obstruct the currents and to create eddies and shoals in their vicinity. In the report previously submitted upon the examination for a site attention was called to the rapid deterioration that is taking place as to depth of water in all the ice-harbors on the Delaware; a result which can be directly ascribed to these costly and bulky piers, which, while excluding the ice, at the same time exclude the tide. The project submitted, whilst not designed to break and hold the ice by sheer weight, is nevertheless sufficiently strong to fend it off, and at the same time offers almost no obstruction to the currents. A summary of the detailed estimate of the cost of the work is herewith appended. Very respectfully, your obedient servant, Maj. W. H. HEUER, Corps of Engineers. A. STIERLE, Assistant Engineer. SUMMARY OF ESTIMATE FOR ICE-HARBOR NEAR LISTON'S POINT. CONSTRUCTION OF IRON PIER IN DELAWARE BAY, NEAR LEWES, DELAWARE. No work has been done during the past fiscal year. The last appro priation made was $13,000, August 2, 1882. This was applied to repairs of the timber superstructure, which was but partially completed. At the end of the last fiscal year it was estimated that about $15,000 would be yet required to remove decayed and defective parts of the superstructure and replace them with sound timber. The decay of the timber superstructure is very rapid, and to make the pier of value the deck must be maintained with unimpaired strength. Four spans of the pier are now loaded with an average weight of about 85 tons per span, and the use of the piers is likely to submit it to weights far in excess of its present load. To render a timber superstructure safe at all times would require that parts weakened by decay should be removed very early in their deterioration and replaced by sound material. This would render the life of the timber used of short duration and make the cost of maintenance large. Again, the uncertainty of appropriations would prevent repairs at such times as they should otherwise be made, thereby placing the work in a dangerous condition. In view of these facts it seems probable that the present timber superstructure could be economically replaced with a permanent iron superstructure at such a cost that the annual interest thereon would be much less than the average cost of annual repairs to a timber superstructure. There has not yet been an opportunity for sufficient study of the subject to submit plans and estimates for an iron superstructure, but these will be made at an early day. The amount required for the existing project is $15,000, which could be profitably er pended, if made available, either in repairs to the present superstrueture, or towards the partial replacing of the same by permanent ironwork. The pier is in the collection district of Delaware, the nearest port of entry beg Wilmington, where the amount of revenue collected during the year ending Dec:2′′ ber 31, 1884, was $32,110.91. The nearest fort and light-house are, respectively, Fot Delaware and the Delaware Breakwater Light. Total appropriations to June 30, 1885..... $368,500 367,612 7 Money statement. July 1, 1884, amount available $1,536 7 July 1, 1885, amount expended during fiscal year, exclusive of outstanding liabilities July 1, 1884.. 9519 July 1, 1885, amount available...... Amount (estimated) required for completion of existing project G II. IMPROVEMENT OF HARBOR AT DELAWARE BREAKWATER, DELAWARE The river and harbor act of July 5, 1884, appropriated $75,000 for continuing this work. During the last fiscal year the work of closing the "gap," or the interval between the breakwater and the ice-breaker. has been in progress. To prevent the scouring action of the tides a foundation of brush-mattresses was sunk along the axis of the gap, and upon this foundation the substructure of the work is placed. The brush-mattresses were 30 feet long, 16 feet wide, and 2 feet thick. and so placed as to cover a width of 90 feet. The length of the gap be tween low-water lines is about 1,390 feet. At the close of the fiscal year ending June 30, 1884, the construction of these mattresses was in progress. During the past fiscal year this work was completed by the construction and placing of 258 mattresses and loading same with 1,813 cubic yards of small stone, and 1,198 tons of large stone. On October 16, 1884, proposals were invited by public advertisement for 23,000 tons of stone to be delivered in the Delaware Breakwater at |