PROTECTIVE WORK.

(29.) The Contractor shall erect all necessary structures, and do all work needed to protect his work from water; he shall erect all temporary dams, coffer dams, sheet-piling and other devices, take care of the river and of the water accumulated behind the temporary dam or dams or other structures, and shall be responsible for all damage that may be caused by the action of water, whether from negligence or any other cause. Such damage is to be repaired, and the work must be restored and maintained at his cost.

(30.) All earth and rock excavation, masonry, timber and other work temporary or permanent, for the purpose of protecting the work from the river, provided that they are not objected to by the Engineer as improper or unnecessary, are to be paid for at the prices stipulated in this contract. All work of this character is to be removed by the Contractor at his own expense, if so ordered by the Engineer.

TIMBER.

(31.) Timber may be ordered used for platforms, for permanent sheet-piling and for other permanent uses. It shall be of the size and placed in the manner ordered by the Engineer.

(32.) All timber and lumber so used shall be spruce, sound, straight-grained, and free from all shakes, loose knots and other defects that may impair its strength and durability. The price bid for timber shall cover all incidental expenses incurred for labor, or for tools and materials used in placing, securing and fastening it.

(33) No payment shall be made to the Contractor for lumber used for bracing, sheeting, scaffolding and other temporary purposes.

(34.) All sheeting and other timber work in the trenches and pits shall be removed unless it is ordered left in, in which case such timber shall be paid for as herein stipulated, clause —, item —, for permanent timber work.

(35.) Tongued and Grooved Timber.-The timber to be used for sheet-piling in the foundations and other places may be ordered tongued and grooved. Such timber shall be furnished and placed as ordered, and the price herein stipulated, clause —, item —, for tongued and grooved timber is to cover the cost of placing, driving, securing and fastening the same.

MASONRY.

(36.) Hydraulic Masonry.-All masonry, except where otherwise specified, shall be laid in hydraulic cement mortar, and shall be built of the forms and dimensions shown on the plans, as directed by the Engineer from time to time, and the system of bonding ordered by the Engineer shall be strictly followed.

(37.) All joints must be entirely filled with mortar, and the work in all cases shall be well and thoroughly bonded.

(38.) Care must be taken that no water shall interfere with the proper laying of masonry in any of its parts.

(39.) All means used to prevent water from interfering with the work, even to the extent of furnishing and placing pipes for conducting the water away from points where it might cause injury to the work, must be provided by the Contractor at his own expense.

(40.) Under no circumstances will masonry be allowed to be laid in water.

(41.) Ironwork.-All ironwork, except the sluice-gates, is to be built in the masonry without other compensation than the price herein stipulated to be paid per cubic yard of masonry.

(42.) No masonry is to be built between the 15th of November and the 15th of April, or in freezing weather, except by permission of the Engineer.

(43.) All fresh masonry, if allowed to be built in freezing weather, must be covered and protected in a manner satisfactory to the Engineer, and during hot weather, all newly built masonry shall be kept wet by sprinkling water on it with a sprinkling pot, until it shall have become hard enough to prevent its drying and cracking.

(44.) Cement.-American cement and Portland cement are to be used. The American cement must be in good condition and must be equal in quality to the best Rosendale Cement. It must be made by manufacturers of established reputation, must be fresh and very fine ground, and in well-made casks (or equally safe and tight receptacles approved by the Engineer). The Portland cement must be of a brand equal in quality to the best English Portland cement. To insure its good quality, all the cement furnished by the Contractor will be subject to inspection and rigorous tests; and if found of improper quality, will be branded, and must be immediately removed from the work; the character of the tests to be determined by the Engineer. The Contractor shall, at all times, keep in store at some convenient point in the vicinity of the work, a sufficient quantity of cement to allow ample time for the tests to be made without

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delay to the work of construction. The Engineer shall be notified at once of each delivery of cement. It shall be stored in a tight building, and each cask must be raised several inches above the ground, by blocking or otherwise.

(45.) Cement is generally to be used in the form of mortar with an admixture of sand, and when so used, its use is included in the price herein stipulated for the various kinds of masonry; for the foundation work, however, Portland cement may be ordered by the Engineer to be used without any admixture of sand in exceptionally wet and difficult places, for grouting seams or for such purposes as he may direct; such cement shall be furnished by the Contractor, and if it is used in connection with masonry, it will be paid for in addition to the price herein stipulated to be paid for said masonry. Such cement is to be paid for at so much per barrel of 400 lbs., furnished and delivered by the Contractor at the place where it must be used. See clause, item -.

(46.) Mortar.-All mortar shall be prepared from cement of the quality before described, and clean, sharp sand free from loam. These ingredients shall be thoroughly mixed dry, as follows: The proportion of cement ordered, by measure, with the ordered proportion of sand, also by measure; and a moderate dose of water is to be afterwards added to produce a paste of proper consistency; the whole to be thoroughly worked with hoes or other tools. In measuring cement it shall be packed as received in casks from the manufacturer. The mortar shall be freshly mixed for the work in hand, in proper boxes made for the purpose; no mortar to be used that has become hard or set.

(47.) The price herein stipulated for the various kinds of masonry is contingent on the use of a mortar made of a mixture of one part in volume of American cement to two parts of sand. Additional prices are herein stipulated for the use of mortars formed with a different mixture of cement and sand. Clause, items

(48.) Concrete.-The concrete shall be formed of sound, broken stone or gravel not exceeding two inches at their greatest diameter. All stone in any way larger is to be thrown out. The materials to be cleaned from dirt and dust before being used; to be mixed in proper boxes, with mortar of the quality before described, in the proportion of five parts of broken stone to one part of cement; to be laid immediately after mixing, and to be thoroughly compacted throughout the mass by ramming till the water flushes to the surface; the amount of water used for making the concrete to be approved or directed by the Engineer. The concrete shall be allowed to set for twelve hours, or more, if so directed, before any work shall be laid upon it; and no walking over or working upon it shall be allowed while it is setting.

(49.) Whenever ordered by the Engineer, the concrete shall be formed of broken stone not exceeding one inch at their greatest diameter, used in the proportion of three parts of broken stone to one part of

cement.

(50.) Bricks.-The bricks shall be of the best quality of hand-made, hard-burned bricks; burned hard entirely through, regular and uniform in shape and size, and of compact texture. To insure their good quality, the bricks furnished by the Contractor will be subject to inspection and rigorous tests, and if found of improper quality, will be condemned; the character of the tests to be determined by the Engineer. They are to be culled before laying, at the expense of the Contractor; and all bricks of an improper quality shall be laid aside and removed; the Engineer to be furnished with men for this purpose by and at the expense of the Contractor.

(51.) Brick Masonry.- All brick masonry shall be laid with bricks and mortar of the quality before described. No "bats" shall be used except in the backing, where a moderate proportion (to be determined by the Inspector) may be used, but nothing smaller than "half-bricks." The bricks to be thoroughly wet just before laying. Every brick to be completely imbedded in mortar under its bottom and on its sides. Care shall be taken to have every joint full of mortar. The face work inside of the GateHouses to be laid with pure Portland cement to a depth from the face of at least one foot.

(52.) Brick Masonry in Asphaltum Mortar.-During the progress of the work some brick work in connection with the roof of the Gate-House and stop-cock vaults way be ordered to be laid in asphaltum mortar. In laying such work the bricks must be heated to such a temperature and the mortar must be made of such mixture of Trinidad asphaltum and plaster of Paris as shall be directed. The mixture to be kept stirred up and at the temperature ordered, and the whole operation to take place under the direction of the Engineer.

(53.) Centering.-All centering shall be made, put up and removed in a manner satisfactory to the Engineer.

STONE MASONRY.

(54.) All stone masonry is to be built of sound clean quarry stone of quality and size satisfactory to the Engineer; all joints to be full of mortar, unless otherwise specified.

(55.) Dry Rubble Stone Masonry and Paving.-Dry rubble masonry and paving are to be laid without mortar, and are to be used for walls, for the slopes of the Dam embankments, and at any other places that may be designated.

(56.) This class of masonry is to be of stone of suitable size and quality, laid closely by hand with as few sprawls as practicable, in such manner as to present a smooth and true surface. The work is to be measured in accordance with the lines shown on the drawings or ordered during the progress of the work. The stones used must be roughly rectangular; all irregular projection and feather-edges must be hammered off. No stone will be accepted which has less than the depth represented on the plans or ordered. Each stone used for paving must be set solid on the foundation of broken stone or earth and no interstices must be left.

(57.) In the dry rubble masonry walls large stones must be used, especially for the faces, and the walls must be bonded with frequent headers, of such frequency and sizes as shall be approved by the Engineer. (58.) Rip-Rap.-Rip-rap may be used in connection with the protective work, and wherever the Engineer may order it. It shall be made of stone of such size and quality and in such manner as he shall direct, and must be laid by hand.

(59.) Broken Stones.-After the slopes which are to receive the paving have been dressed, a layer, twelve inches thick, of broken stone is to be spread as a foundation for the paving, wherever ordered. The broken stones must be sound and hard, not exceeding two inches at their greatest diameter. Broken stone, not exceeding one inch in diameter, may be used for forming roadways; it is to be spread to such thickness as ordered and heavily rolled or rammed. Broken stones may be used also wherever the Engineer may direct, rolled if so directed, and paid for under this head, except the broken stone used for making concrete, the cost of which is included in the price hereinbefore stipulated for concrete laid. (60.) Rubble stone masonry is to be used for the central part of the Dam, for the centre walls of the earth embankments, for most of the structures and appurtenances of the Dam, and wherever ordered by the Engineer.

Rubble stone masonry shall be made of sound, clean stone of suitable size, quality and shape for the work in hand, and presenting good beds for materials of that class. Especial care must be taken to have the beds and joints full of mortar, and no grouting or filling of joints after the stones are in place will be allowed. The work must be thoroughly bonded. The up-stream face of the centre walls shall be closely inspected after they are built, and if any mortar joints are not full and flush, they shall be taken out to a depth of no less than two inches or more, if so ordered, and repointed properly.

(61.) Central Part of the Dam and Overflow.-A large quantity of rubble stone masonry in mortar is to be used in the construction of the central part of the Dam and of the overflow.

The stones used therein must be sound and durable; they must have roughly rectangular forms, and all irregular projections and feather-edges must be hammered off. Their beds, especially, must be good for materials of that class, and present such even surfaces that, when lowering a stone on the level surface prepared to receive it, there can be no doubt that the mortar will fill all spaces. After the bed joints are thus secured, a moderate quantity of spauls can be used in the preparation of suitable surfaces for receiving other stones. All other joints must be equally well filled with mortar.

The quality of the beds is to regulate, to a large extent, the size of the stones used, as the difficulty of forming a good bed joint increases with the size of the stones.

Various sizes must be used.

Generally the largest stones are not to measure more than twenty cubic feet, and they are to be used in the proportion of about 25 per cent. of the whole; but they must be omitted partially or entirely if their beds are not satisfactory. It is expected that one-quarter of the stones used in the main body of the Dam, which is built of rubble, will be of such size that two men can handle them, or even smaller. The balance to be composed of intermediate sizes. Regular coursing is to be avoided.

(62.) Face Work for Rubble Stone Masonry.-The exposed faces of the wing walls, retaining walls and of any other rubble work that the Engineer may designate, are to be made of broken ashlar with joints not exceeding one-half inch in thickness; the stones not to be less than 12 inches deep from the face, and to present frequent headers. This face work to be equal in quality and appearance, although with smaller stones, to the face of the breast wall in front of the proposed new Gate-House at Croton Dam (section 1), and to be well pointed. This face work is to be paid by the square foot of the superficial area for which it is ordered, in addition to the price paid per cubic yard of rubble stone masonry.

(63.) Block Stone Masonry.-Block stone masonry is to be composed mainly of large blocks and is to be used for the steps of the overfall or for other steps, or whenever and wherever ordered by the Engineer. It is to be laid in cement mortar, well pointed, or may be ordered laid dry at the price stipulated in clause, item —.

This stone, which is to receive the shock of water and ice, is to be especially sound, hard and compact, and of a durable character; it is to be prepared to the dimensions given, so that no joint will in any place be more than one inch wide.

(64.) Facing Stone Masonry.-The outer faces of the Masonry Dam and of its gate chamber, of the overflow (except steps), and of any other piece of masonry that may be designated, are to be made of range stones, as shown on the plans, the stone to be of unobjectionable quality, sound and durable, free from all seams, discoloration and other defects, and of such kind as shall be approved by the Engineer.

(65.) All beds, builds and joints are to be cut true (for the gate chamber to a depth of not less than 6 inches from the faces, and for the Dam to a depth of not more than 4 inches, and not less than 3 inches from the faces), to surfaces allowing of one-half inch joints at most; the joints for the remaining part of the stones not to exceed two inches in thickness at any point.

(66.) All cut arrises to be true, well defined and sharp.

(67.) Where this class of masonry joins with granite dimension stone masonry the courses must correspond, and the joining with arches and other dimension stone masonry must be a.curate and workmanlike. Each course to be composed of two stretchers and one header alternately, the stretchers not to be less than 3 feet long nor more than 7 feet long, and the headers of each successive course to alternate approximately in vertical position.

(68.) The rise of the courses may vary from bottom to top from 30 inches to 15 inches in approximate vertical progression, and the width of bed of the stretchers is not to be at any point less than 28 inches. The headers are not to be less than 4 feet in length.

This class of masonry, for the faces of the Dam and gate chamber, including the headers, is to be estimated at 30 inches thick throughout. At other places that may be designated by the Engineer the size of the stones is to be established by him, and the facing stone masonry is to be estimated according to the lines ordered or shown on the plans. In no case are the tails of the headers to be estimated.

The work to be equal in quality and appearance to the facing stone masonry work now being built by the Aqueduct Commissioners for their Masonry Dam across the East Branch of the Croton River near Brewster.

(69.) The coping of the wing walls, of the side walls to the spill-way, and any other copings that may be designated, will be classed as facing stone masonry.

(70.) The price herein stipulated for facing stone masonry is to cover the cost of pointing, of cutting chisel drafts at all corners of the Gate-House Dam and other corners, and of preparing the rock faces; but if any six-cut or rough-pointed work is ordered in connection with this class of masonry it shall be paid for at the prices herein stipulated for such work. Clause —, items and —.

(71.) The face bond must not show less than 12 inches lap, unless otherwise permitted.

(72.) The pointing of the faces to be thoroughly made with pure Portland cement after the whole structure is completed only; unless otherwise permitted, every joint to be raked out therefor to a depth of at least two inches, and if the Engineer is satisfied that the pointing at any place is not properly made, it must be taken out and made over again.

(73.) Granite Dimension Stone Masonry.-Granite dimension stone masonry must be made of first-class granite of uniform color, free from all seams, discoloration and other defects, and satisfactory to the Chief Engineer.

(74.) It is to be used for the arches and gate openings in the gate chamber, for the cornice work of the Dam, for the Gate-House superstructure and for the crest and first step of the overflow, and at any other place that may be designated by the Engineer.

(75.) The stones shall be cut to exact dimensions, and all angles and arrises shall be true, well defined and sharp.

(76.) All beds, builds and joints are to be dressed, for the full depth of the stone, to surfaces, allowing of one-quarter (1) inch joint at most. No plug-hole of more than 6 inches across or nearer than 3 inches from an arrise is to be allowed, and in no case must the aggregate area of the plug-holes in any one joint exceed one-quarter of its whole area.

(77.) The stone shall be laid with one-quarter (†) inch joints, and all face joints shall be pointed with mortar made of clear Portland cement, applied before its first setting. All joints to be raked out to a depth of one inch before pointing; the cost of pointing to be included in the price stipulated for cut stone masonry. (78.) Face Dressing.-The exposed faces of the cut stone are to be finished in various ways, in accordance with the various positions in which they are placed. They shall be either left with a rock or quarry face, rough-pointed, or fine-hammered (six-cut work).

(79.) The various classes of face dressing must be equal in quality and appearance to those on the sample in the office of the Chief Engineer.

(80.) Rock Face Dressing. In rock face work the arrises of the stones inclosing the rock face must be pitched to true lines; the face projections to be bold, and from 3 to 5 inches beyond the arrises. The angles of all walls on structures having rock faces are to be defined by a chisel draft not less than 1 inches wide on each face.

(81.) Rough Pointed Dressing. In rough-pointed work, the stones shall at all points be full to the true plane of the face, and at no point shall project beyond more than inch, the arrises to be sharp and well defined. Each stone to have its arrises well defined by a chisel draft, which is included in the price for rough-pointed dressing.

(82.) Fine Hammered (Six-Cut) Dressing.--In fine-hammered work the face of the stones must be brought to a true plane and fine-dressed, with a hammer having six blades to the inch.

(83.) In measuring cut stone masonry, when the stones are not rectangular, the dimensions taken for

each stone will be those of a rectangular, cubical form which will just inclose the same. The price herein stipulated for granite dimension stone masonry is to cover the cost of preparing the rock faces, and of making the chisel drafts, of preparing all holes and recesses and grooves and of pointing.

(84.) No payment will be made for cutting grooves and recesses other than the price paid for the dressing of their surfaces, which are to be fine-hammered.

(85.) For rough-pointed and fine-hammered (six-cut) dressing, a price per square foot of dressing wiil be paid in addition to the price per cubic yard of masonry, viz.:

(86.) For rough-pointed dressing, the price stipulated in clause, item -), and for fine-hammered (six-cut) dressing, the price stipulated in clause, item (-).

(87.) The broken ashlar in the superstructure of the gate chamber and the cut paving in the GateHouse, are to be estimated as granite dimension stone masonry.

(88.) The exposed parts of the cut stone, including the ashlar masonry of the superstructure, are generally to be prepared with rock face.

(89.) The inside surfaces and copings are generally to be rough-pointed.

(90.) All the gateways, grooves, sills, floors, and all other surfaces designated by the Engineer are to be fine-hammered.

Ironwork, stop-cocks, sluice-gates, doors and windows (similar to the specifications given on pages 258, 263, and 256).

SPECIFICATIONS OF DEPARTMENT OF PUBLIC WORKS FOR PUMPINGENGINES, BOILERS AND APPURTENANCES. (NEW FUMPING

STATION AT 179TH STREET AND 10TH AVENUE.)

The work to be done consists in furnishing all of the material and labor and performing all the work necessary to build and erect complete, in a building to be erected at the New Aqueduct, between Tenth Avenue and Harlem River, two vertical triple expansion ten-million gallon pumping-engines, boilers and appurtenances complete, and two vertical triple expansion four-million gallon pumping-engines, boilers and appurtenances complete.

Capacity. Each reservoir service engine shall have capacity to deliver 10,000,000 United States gallons of water in twenty-four hours.

Each tower service engine shall have capacity to deliver 4,000,000 United States gallons of water in twenty-four hours.

Pressures.—The water pressure on the plungers will be, in the case of the reservoir service engines, 56 pounds per square inch. _

In the case of the tower service engines, the water pressure will be 105 pounds per square inch.

This includes friction in the pipes. There will be a pressure on the suction of about 15 pounds in both cases.

The steam pressure in each case shall be 160 pounds above atmosphere at the boilers. Condensers.-The condensers shall be of the surface type, and there will be one for each engine, situated in the suction main and so arranged that the water, or part of the water, pumped by the main engine will pass through it, so that no water will be wasted for injection.

The tubes will be of brass or copper, and there shall be some arrangement to permit of the necessary expansion and contraction of tubes.

There must be provided some arrangement by which the temperature of the condensed water can be kept practically constant during such variations in the temperature of the cooling water as are liable to occur. The air pump may be independent or attached, but must be of ample capacity to handle all leakages and maintain a satisfactory vacuum.

There must also be furnished a cast-iron hot well with proper vapor-pipe, to collect the discharge from the air-pump.

Foundations.-The City will provide concrete sub-foundations for the boilers to a level with the bottom of boiler saddles or ash-pits, and for the engines to a level 21 feet below the engine-room floor.

All foundations and masonry of any character for either engines or boilers above this point must be provided by the Contractor and included in the proposition.

Space. The engines and boilers will be generally located as shown in accompanying plan.

Bidders must show a plan of the engine and boiler rooms to scale showing dimensions, etc., necessary for the machinery offered.

Pipes.-The suction-pipes with tees and stop-cocks left for provisional engines shall be furnished, connecting the engines with tank in building.

The delivery pipes with blank tees and stop-cocks left for provisional engines shall be furnished,