work is being done with steam-shovels. The excavation and masonry required for the new loop for the old aqueduct at the new dam has been almost finished. The rock and earth excavation for the channel on the side-hill in front of the overflow-weir, is nearly completed. The total amount of work done under the contract to January 1, 1895, amounts to about $800,000.

The Jerome Park Reservoir.-We have stated on page 114 that the Aqueduct Commissioners decided in 1884 to construct a new receiving reservoir at Jerome Park, in the Annexed District of the city. This site was the only one that could be found within or near the city, where the surface of the ground was near the required elevation to a sufficient extent. Owing to various causes of delay, the plans for the Jerome Park reservoir were not prepared until 1894. A contract for the work was made with John B. McDonald on August 23, 1895.

The basin will be formed by building earthen embankments with masonry core-walls at depressions where they are required to retain the water, and by excavating the high points on the reservoir site. The embankments will generally be of moderate height, the maximum being 35 feet above the surface in the northwest part of the reservoir. The total amount of rock and earth excavation that will be required is estimated at about 7,000,000 cubic yards. In order to insure water-tightness, the whole bottom of the reservoir is to be covered with 3 to 6 inches of concrete. The embankments will be made as shown on Plate 134. The inner slopes are to be covered to an elevation 2 feet above the water-line, with 4 to 8 inches of concrete, the lower part being faced with a 4-inch course of brickwork and the remaining portion with paving-stone, 15 inches deep, laid dry on a bed of

mortar.

The reservoir will have a water-surface of about 228 acres, and will store about 1,900,000,000 gallons. This storage will raise the total amount of water in the reservoirs within the limits of the city to 3,234,000,000 U. S. gallons. As these reservoirs cannot be entirely emptied without causing great inconvenience and hardship from the reduction of pressure in the mains that would result, only about half of the above total amount of storage is to be considered available.

The Jerome Park reservoir is to be fed by both the old and the new aqueduct. At present the former passes through the proposed basin on an embankment, while the latter passes beneath it in a tunnel, located about 115 feet below the surface, with which it is connected by shaft No. 21, now closed by a temporary timber bulkhead. According to the plans adopted, the new aqueduct is to be brought to the reservoir by a branch conduit about 7500 feet long, which will leave the aqueduct at station 1268 + 02.5 (see Plate 133) just before the depressed part of the conduit begins, and will follow the line of the old aqueduct to Jerome Park. Both conduits are to be carried into the reservoir on a masonry structure, founded on rock, to a large inlet gate-house (see Plate 133). The masonry structure continues through the reservoir, and divides it into an east and a west basin. The old aqueduct is carried on top of this division-wall through the reservoir. By

means of the arrangement of the gate-houses described hereafter, either of the aqueducts can discharge its water into the reservoir or convey it further into the city.

In order to control the inlet and outlet of the reservoir five gate-houses are. to be constructed (see Plate 133), viz.: gate-house No. 1, at the point where the branch conduit leaves the new aqueduct; gate-houses Nos. 2, 3, and 4, at different points on the reservoir embankment for controlling the outlet; gate-house No. 5, at a central point in the reservoir, for regulating the inlet through either or both of the aqueducts.

Gate-house No. 1 (see Plate 135) will form an "L" in plan, the main building being 31 X 35 feet, and the wing 22 X 27 feet. The branch conduit leaves the wing of the gatehouse at right angles (westerly) to the direction of the main aqueduct. It is to have a "horseshoe" cross-section, 11.40 feet wide and 13.53 feet high. A central pier in the gate-house will divide the water flowing toward the branch conduit into two streams, each 6 feet wide. Four 2' X 10' sluice-gates will control the inlet-openings to the branch aqueduct, which are to be constructed in a cross-wall in the water-chamber of the wing of the building. In the sides of the wing and main water-chambers grooves are to be provided for stop-planks for shutting off the main or branch aqueducts from the city.

Gate-houses Nos. 2, 3, and 4 (see Plate 133) will be constructed to control the outlet from the reservoir. Each is to have two inlet-chambers, one for drawing water from the reservoir at the gate-house at different levels, and the other for drawing water from the further division of the reservoir by means of two 48-inch pipes, which are to be laid on the bottom of the reservoir, and are to be connected with the central inlet gate-house (No. 5), as described hereafter. The two water-chambers of each of the outlet gate-houses are to be connected by an arched passage to be constructed in the partition-wall between them.

Two 48-inch outlet-pipes are to be laid from each of these gate-houses, and are to be connected with the pipe system of the Annexed District. These pipes will be laid in brick culverts through the embankments of the reservoir. Each outlet-pipe will be controlled by a stop-cock, which will be placed in a chamber of the gate-house. At each inlet from the reservoir, grooves will be provided in the masonry. They will ordinarily be used for wire screens, and, in case of necessity, for stop-planks for closing the connection with the reservoir. Drain-pipes for emptying the water-chambers will be laid at each gate-house.

The general plan for gate-houses Nos. 3 and 4 is shown on Plate 137. Each is to have a substructure about 29 X 35 feet in plan. The top inlet of the chamber drawing water from the near division of the reservoir will be at right angles to the bottom and middle inlet.

Gate-house No. 2 (see Plate 136) will be 37 X 40 feet in plan. In addition to the chambers provided for Nos. 3 and 4, it will have a central chamber into which the waste water from the reservoir will pass over three waste-weirs (each 6 feet wide), the height of which will be regulated by stop-planks. One of these weirs will be constructed in the main-wall of the substructure, and the other two in the walls separating the water-chambers from the wastechamber. A 20-inch waste-pipe will be laid from gate-house No. 5 to the waste-chamber of No. 2. This chamber will be connected by means of a masonry culvert with a sewer near

by. Provision will be made for placing two 2' X 5' sluice-gates in the cross-wall of gate-house No. 2 in case they should be required.

Gate-house No. 5 (see Plates 138 to 142, inclusive) is to be constructed on the division-wall of the reservoir at the point shown on Plate 133. It is to serve for the following purposes:

Ist. To receive the water from the old aqueduct and the branch of the new aqueduct.

2d. To discharge this water into the east or the west division of the reservoir, or into both; or to let it pass to the city in the new or the old aqueduct without entering the

reservoir.

3d. To form a connection between the two divisions of the reservoir.

4th. To control the inlet into the 48-inch pipes laid from gate-houses Nos. 2, 3, and 4, to this gate-house.

5th. To connect the new aqueduct (located in a tunnel 115 feet below the surface) by means of shaft No. 21 with the reservoir.

Gate-house No. 5 will be arranged to maintain a supply to the city when either or both divisions of the reservoir are empty.

The gate-house will have in plan the form of a cross. It will contain a large inlet water-chamber, which will be divided by a central cross-wall, provided with openings controlled by sluice-gates, into an east and a west section. The branch from the new aqueduct will enter the former and the old aqueduct the latter. On the north the inlet-chamber will be connected with a small water-chamber (14 X 18 feet in plan), from which the inlet into a masonry conduit leading to and connected with shaft 21 will be controlled by means of sluice-gates. By this arrangement the water entering the inlet-chamber can be turned into the new aqueduct.

From the west section of the inlet-chamber a new conduit is to be built for the old aqueduct around the gate-house and to be continued on top of the division-wall to the southern extremity of the reservoir, where it is to be joined to the old aqueduct.

A short masonry conduit will lead the water from the east section of the inlet-chamber to the outlet-chamber to be constructed at the south end of the gate-house. From the latter chamber two circular masonry conduits, which are to be constructed in the divisionwall, each 12 feet in diameter, will convey the water to a point about 2000 feet south of the gate-house, where the conduits will terminate. Here the water will be discharged from the two conduits respectively into the east and west divisions of the reservoir. By discharging the water in this manner and drawing from gate-house No. 5. a circulation will be produced in the reservoir. The inlet into the conduits just described will be controlled at the outletchamber of the gate-house by means of sluice-gates and stop-planks.

Below the bottom of the water-chambers mentioned above, other water-passages are to be provided. Just north of the inlet-chamber of the branch conduit leading to shaft 21, two arched passages will connect the two divisions of the reservoir. For each passage a small chamber, provided with two sets of grooves for stop-planks, will be constructed in the gatehouse. Two similar arched passages are to be constructed under the main inlet-chamber.

THE WATER-SUPPLY OF THE CITY OF NEW YORK.

Provision will be made for closing each of these passages by sluice-gates and by means of stop-planks.

The 48-inch mains to be laid from gate-house Nos. 2, 3, and 4 to No. 5 will terminate at this gate-house and will be continued by arched passages to be constructed in the gate-houses and to be controlled by sluice-gates and stop-planks, as shown on Plate 139. These passages will enable each set of 48-inch mains to draw water from the far side of the gate-house.

In gate-house No. 5 all the sluice-gates are to be either 2 X 10 feet or 2 X 8 feet, placed in pairs. Arrangements will be made for relieving the back-pressure on the gates before they are opened. A complete drainage system will be provided. A 20-inch drain-pipe will convey the waste water to gate-house No. 2, where it will be discharged as described on page 211.

212

APPENDIX I.

MACHINERY AND APPLIANCES USED IN CONSTRUCTING THE NEW CROTON AQUEDUCT.

Air-Compressors.-Three kinds of air-compressors were used the Ingersoll, the Rand, and the Norwalk. As great improvements have been made during the past ten years. in this kind of machinery, the reader must bear in mind that the compressors described below represent the styles manufactured in 1885 and not the improved machines made

now.

The Ingersoll "Straight Line" Air-compressor is shown on Plate 145. The frame or bed-piece, to which the compressor is anchored by eight strong bolts, is made in one casting, the parallel sides being stiffened by heavy transverse ribs. The steam- and air-cylinders are placed in a straight line upon the bed-piece and are connected at the top by heavy tierods. The piston-rods of both cylinders are attached to the same cross-head, a solid wrought-iron forging, bearing on the frame and having top and bottom brasses running on guides. In all engines above twelve inches in diameter the piston-rod of the air-cylinder extends through the back-head and is supported outside of the cylinder by an adjustable bearing, which relieves the cylinder from supporting the whole weight of the piston and thus avoids much wear and leakage. The steam- and air-pistons are similar, each being fitted with two anti-friction, self-packing, metallic piston-rings, made of cast-iron for the former and of composition metal for the latter.

Two well-balanced fly-wheels are provided to give a uniform motion to the compressor. They are forced upon and keyed to a heavy main shaft, placed near one end of the frame. The connecting-rods are fastened at one end to the cross-head and at the other to the crankpins of the fly-wheels.

The smaller engines have ordinary slide-valves, cutting off at three quarters of the stroke, but those over fourteen inches in diameter are provided with Meyer's adjustable cut-off. Eccentrics keyed to the main shaft transmit motion to the steam-valves by means of rockers, fastened to a special rock-shaft, and having their upper arms connected to the valve-stems,

Each head of the air-cylinder is provided with patent inlet- and discharge-valves of the poppet type. They are made of phosphor bronze, and are light and noiseless in motion. As they work in cages screwed to the cylinder-heads from the outside, they can be examined or removed without removing the cylinder-heads. The cooling of the air during compres