882

The Water Supply of New York City-Continued.

below sea level, between a shaft at Storm King Mountain on the west bank and another shaft on the east side of the river at Breakneck Mountain. The top of the west shaft is closed by a deep concrete plug, but the east shaft, which is the drainage and access shaft for the Moodna-Hudson-Breakneck pressure tunnel, as well as a waterway, required a removable cover, and for it steel castings and forgings of unusual size and shape had to be manufactured. The drainage shaft is fourteen feet in diameter inside the concrete inner lining, which protects the fifteen-foot-diameter steel interlining, outside of which concrete is solidly packed against the rock. About ten feet above sea-level, this shaft is covered by a steel casting nearly hemispherical in shape. This dome rests on a cast steel ring called the curb. To hold the dome in place against the pressure of the water when the aqueduct is in service, which at this point is 180 pounds per square inch, equivalent to a head of 410 feet, there are thirty-six anchor bolts, each 41⁄2 inches in diameter and 50 feet long, made of nickel-chrome steel. These bolts go through bored holes in the flange of the dome and the curb, and through steel sleeves to a cast steel anchor ring 46 feet farther down. The object of these sectional steel sleeves is primarily to insure the application of the anchorage stresses at a suitable depth in the rock, secondarily to permit te removal of the bolts if desired in connection with the removal of the cover or for inspection and also for convenience and necessary adjustments during construction operations. The top and bottom sections of these sleeves are of cast steel, each with forty-seven collars on the outside to afford a good grip on the concrete; the middle sections are commercial pipe.

Steel pipe siphons were used in valleys where the rock was not sound or where for other reasons pressure tunnels would be impracticable. These steel pipes are made of plates from 7-16-inch to 4-inch in thickness, riveted together, and are 9 feet and 11 feet in diameter. They are lined with 2 inches of cement mortar, enveloped with concrete and covered with an earth embankment. There are fourteen of these siphons, aggregating six miles. Three pipes are required in each siphon for the full capacity of the aqueduct, but only one pipe has been completed in all the siphons. The remaining pipes are now needed and must be constructed as soon as market conditions will permit. These pipes are not true siphons, but are given this name because of their approximate resemblance to an inverted siphon.

HOW THE WATER IS PROTECTED.

At the Ashokan reservoir, and also at Kensico reservoir, aerators have been built. The aerators are substantially alike and are great fountain basins, approximately 500 feet long by 250 feet wide, each containing about 1,600 nozzles, through which jets of water are thrown vertically into the air. permitting thorough admixture of oxygen from the atmosphere and removal of undesirable gases and other matters causing tastes and odors.

Within the screen chamber down stream from Kensico reservoir chlorine is introduced into the water flowing in the aqueduct for the destruction of germ life. The gas is delivered at the chamber compressed to a liquid state in steel containers holding one hundred pounds each. Chlorine is used to insure the practical sterilization of the water before it goes to the city and is wholly neutralized or dissipated before the water reaches the distribution pipes. In addition to the treatment whenever required by the methods outlined above, Catskill water constantly receives benefit from its long storage in the great reservoirs of thẹ system. In them sedimentation, bleaching by the sun, oxygenation by the winds and sterilization by natural processes, all go on more or less continually.

THE CITY TUNNEL.

From Hill View reservoir, Catskill water is delivered into the five boroughs by a circular tunnel In solid rock reducing in diameter from 15 to 14, 13, 12, and 11 feet. The total length of the tunnel is eighteen miles. From two terminal shafts in Brooklyn, steel and cast iron pipe lines extend into Queens and Richmond. A 36-inch flexible-jointed, cast iron pipe, burled in a trench in the harbor bottom, has been_laid across the Narrows to the Staten Island shore, whence a 48-inch cast iron pipe extends to the Silver Lake reservoir, holding 435,000,000 gallons. The total length of this delivery-system is over thirty-four miles. The tunnel is at depths of 200 to 750 feet below the street surface, thus avoiding interference with streets, buildings, subways, sewers and pipes. These depths are necessary, also, to secure a substantial rock covering to withstand the bursting pressure of the water inside and afford the requisite watertightness. The waterway of the tunnel is lined throughout with Portland cement concrete.

The city tunnel, which is the longest tunnel in the world for carrying water under pressure, or for any other purpose, was constructed from twenty-five shafts, including the downtake shaft at Hill View reservoir. about 4,000 feet apart, located in parks and other places where they interfered very little with traffic. Through twenty-two of these shafts the water is delivered into the street mains. These connections from the tunnel to the mains are made by means of vertical riveted steel pipes (called risers) embedded in concrete in the upper part of each shaft and lined with concrete to prevent corrosion inside. Concrete alls all spaces outside the risers, sealing the shafts against the escape of water excepting through the pipes. Provision is made at Shaft 11 in Morningside Park and at Shaft 21 on the shore of the East River, at Clinton and South Streets, Manhattan, for unwatering the tunnel, whenever necessary, for inspection, cleanIng or repairs. Unusual features in connection with the operation of the tunnel are the bronze riser valves in the shafts. The former are located about 100 feet below the top of sound rock and are designed to close automatically in case of an important break in the valve chamber or in the street mains. They can also be closed by hand from within the chambers at the shaft tops.

The cost of the portions of the Catskill Aqueduct within the city limits, including the tunnel, pipe lines. appurtenances and Silver Lake reservoir, is $23,000,000. SHAFTS OF THE CITY TUNNEL.

193d St. and Central Park.

14

79th St. in Central Park.

65th St. in Central Park.

16

50th St. and Sixth Ave..

Sixth Ave. in Bryant Park

18

24th St. and Broadway, Madison

216

Square.

19

6th St. and Fourth Ave., Cooper

240

Square..

Delancey and Eldridge Sts.

Clinton and South Sts...

22

Sands and Bridge Sts., Brooklyn.

23

Flatbush Ave. and Schermerhorn

439

Ft. Greene Park at Myrtle Ave.
Brooklyn...

260

SILVER LAKE RESERVOIR.

The terminal Silver Lake reservoir for the Catskill water system, located on Staten Island, is about 2,400 feet long and 1,500 feet wide It holds 435,000,000 gallons. Earth embankments close natural de

The Water Supply of New York City-Continued.

883

pressions in the ground and a dividing dike payed with concrete forms two basins. From a gate chamber built in this dike, reinforced concrete conduits extend to the boundary of the reservoir, and cast iron pipes prolonged from them connect with the Narrows siphon and with the Staten Island service mains.

In order that the Catskill aqueduet might be most safely and economically located, extensive surveys and sub-surface explorations were made of both topographical and geological character. It was necessary for the board's engineers to make about 3,000 miles of line surveys, besides the very extensive topographical surveys of the reservoir sites and the final location of the aqueduct. For determining the exact location of the deep valley crossings, geological explorations by means of borings into the rock, with diamond and shot drills, were necessary, and were carried on under the immediate supervision of skilled, practical gealogists. Such explorations were also made for the locations of the dams and for other features of the work. In the aggregate, these borings amounted to 240,000 feet, or forty-five miles. Some deep and difficult drilling was required also in connection with the location of the city tunnel and its shafts, particularly in the lower cast side of Manhattan Island, where the old bed of the East River was crossed, which lies west of the present location of that river. Hundreds of test pits, auger borings, wash-drill borings and other formus of sub-surface explorations were used in various parts of the aqueduct. The extensive and useful information gained in this way was of great aid to the engineers designing the works and to the contractors in bidding on their construction.

MAXIMUM MONTHLY CONSTRUCTION PROGRESS.

Grade tunnel excavation, 425 linear feet; pressure tunnel excavation, 5301⁄2 linear feet; shaft excava tion, 183 linear feet; concreting cut-and-cover aqueduct, 1,740 linear feet; concreting grade tunnel, 2,453 Linear feet; concreting pressure tunnel, 2,834 linear feet; concreting shaft, 310 linear feet; placing masonry in Kensico dam, Contract No. 9, 84,450 cubic yards.

Laying 66-inch steel pipe, week, 1,409 linear feet; laying 48-inch cast iron pipe, week, 1,748 near feet; laying 36-inch submerged pipe, week, 984 linear feet.

Cast steel dome on top of drainage shaft, Hudson tunnel, 46.25 tons: bronze section valve, city tunnel, 66-inch, 20.5 tons; bronze riser valve, city tunnel, 72-inch, 21.4 tons; bronze riser valve, city tunnel, 48-inch; 9.4 tons: bronze shaft cap, city tunnel, 72-inch by 48-inch by 48-inch, 11.8 tons; bronze shaft cap, Gay tunnel, 48-inch by 30-inchi by 30-inch, 4.8 tons.

ELEVATIONS ABOVE TIDE IN NEW YORK HARBOR.

Ashokan reservoir, east basin, 587 feet; Ashokan reservoir, west basin, 590 feet: aqueduct at headworks (flow line), 511 feet; Kensico reservoir, 355 feet; aqueduct at Kensico lower gate chamber, 330 feet; water level, eastview filters, 322 feet; aqueduct at tilter effluent (dow line), 312 feet; Hill View reservoir, 295 feet; Silver Lake reservoir, 228 feet.

When the city tunnel is in service, water can be delivered in lower Manhattan at an elevation 260 feet above tide level and in Brooklyn about 240 feet above tide level, under working conditions.

DISTANCES FROM ASHOKAN RESERVOIR.

To Hudson River crossing, 45 miles; to Croton Lake, 64 miles; to Kensico reservoir, 75 miles; to Hill View reservoir (New York City line), 92 miles; to Silver Lake reservoir, 119 miles.

Earth excavation in open cut. 16,000,000 cubic yards; earth excavation in tunnel, 50,000 cubic yards; rock excavation in open cut, 1,000,000 cubic yards: rock excavation in tunnel, 2,700,000 cubic yards; masonry in open cut, 4,200,000 cubic yards; masonry in tunnel, 1,100,000 cubic yards; cement, 6,700,000 barrels; cast iron, 27,000 tons; steel, 32,000 tons; bronze and brass, 3,000,000 pounds.

CHRONOLOGY OF THE WORK.

Report to Manufacturers' Association; sources west of IIudson River, considered for Brooklyn, March 15, 1897; Constitutional amendment passed exempting water supply bonds from debt limit, November 8. 1904: Board of Water Supply Commissioners appointed by Mayor McClellan, June 9, 1905; Chief Engineer began his duties, August 1, 1905; plan for development adopted by Board of Estimate and Arportionment, October 27, 1905; development of watersheds of Esopus, Rondout and Catskill Creeks, approved by State authorities, May 14, 1906; experimental shaft, now west shaft, of Hudson pressure tunnel, begun February 23, 1907; first sod turned, with appropriate ceremonies, by Mayor McClellan, near Garrison, June 20, 1907; police bureau established, February 28, 1908; first concrete placed for aqueduct structure, near Peekskill, April 28, 1908; Brst masonry laid for Olive Bridge dam, Ashokan reservoir, September 19, 1908: maximum contractors' forces, 17,243 men, at active field work, August 23, 1911; maximum contractors' earnings, $2,214,000 for month, November, 1911: headings of Hudson pressure tunnel met, and holeing through" shot fired by Mayor Gaynor, January 30, 1912; storage of water in Ashokan reservoir begun, September 9, 1913; last heading in city tunnel between Shafts No. 8 and 9, "holed through" by Mayor Mitchel, January 12, 1914; began filling Kensico reservoir with Catskill water, November 22, 1913; began Alling Hill View reservoir with Catskill water, November 30, 1915; first delivery of Catskill water into distribution pipes of New York City, December 27, 1915; transfer of maintenance of Esopus watershed and operation of completed reservoir and aqueduct structures, to Department of Water Supply, Gas and Electricity, August 1, 1917; civic celebration of Introduction of Catskill water into New York City, October 12, 13, 14, 1917.

GIVING NEW YORK CITY FIRE PROTECTION.

High Pressure Fire Service System—The high pressure fire service system in Manhattan is bounded by Thirty-fourth Street, Madison Avenue, Twenty-fourth Street, Lexington Avenue, Fourteenth Street. Third Avenue, Bowery, Houston Street, East River, Battery, North River. There are two pumping stationsGansevoort and West Streets, and Oliver and South Streets. Each station has six electrically driven centrifugal pumps. Elther fresh or salt water may be used. Each pump can deliver 3,000 gallons a rainute. The combined capacity of the two stations is equal to about üfty fire engines. The distributing system consists of 128 miles of mains, eight to twenty-four inches in diameter, and about 2,750 four-nozzle hydrants. There are approximately 696 telephones communicating with Fire Department headquarters and with the main and subsidiary stations of the New York Edison Company, from which the necessary electric power is obtained. The present system cost about $7,380,000.

In Brooklyn there are two high pressure fire service systems. The one for the business and manufacturing districts is bounded by the Navy Yard, St. Edward's Street, St. Felix Street, Fort Greene Place, Fifth Avenue, Twenty-fourth Street, Fourth Avenue, Thirty-ninth Street and the water front, covering an area of 4.8 square miles. The supply is furnished by two stations, one located at the foot of Joralemon Street, and the reserve at Willoughby and St. Edward's Streets. Both draw their supply from the Ridgewood mains. The main station is connected to the East River. The pumps are electrically operated in both stations, and have a combined rated capacity of 24,000 gallons per minute. The distributing system consists of about forty-five miles of mains, eight to twenty inches in diameter.

The Coney Island high pressure system protects an area of 470 acres. The pumping station is located sant West Twelfth Street and Coney Island Creek. The total capacity is 4,500 gallons per minute. The water is distributed through six miles of mains.

884

Plants of the Catskill Aqueduct Region.

THE WATER SUPPLY OF NEW YORK CITY—Continued.
STATISTICS OF ASHOKAN, KENSICO AND SCHOHARLE RESERVOIRS.

* Proceedings just begun.

40 miles
10

2,500,000 cu. yds.
7,300,000 cu. yds.

900,000 cu. yds.

1,200,000 barrels

3,000

3 935

None
13 miles
13 miles
2

725,000 cu. yds. (b) 681,000 cu. yds. (b) 319,000 cu, yds. (b) 350,000 barrels (b) +

(a) Earth, 500 feet. (b) For dam only. † Construction not yet begun.

PLANTS OF THE
THE CATSKILL

AQUEDUCT

REGION.

(By Norman Taylor, for a Brooklyn Botanic Garden Leaflet.)

FROM near sea-level to the highest mountains, within one hundred miles of the city stretches the Catskill water system, and this diversity of elevation suggests at once a division of the plant life of the area into the mountain and lowland types of vegetation. This may not be such an artificial division as at first sight appears when it is remembered that many of our local wild flowers are found only on the mountain tops of the Catskills or at elevations in excess of 1,500 feet. Others, again, common enough near the mouth of the Hudson, seem to creep rather sparingly up the valley, perhaps as far as the Highlands, only to find these * hills a barrier to a more northerly journey.

There are many striking illustrations of these well marked tendencies of plant distribution in the region. For instance, near the mouth of the Croton River there is a tree of the yellow pine (Pinus echinata), more than fifty miles north of its usual home, near the pine barrens of New Jersey. And on the Palisades, opposite Yonkers, there grew, until quite recently, large masses of the native yew (Taxus canadensis), otherwise at home in the highland region northward. Near Peekskill Bay and just below it on Verplanck Point are many specimens of the ninebark (Physocarpus opulifolius), which, while it is common enough northward, is rare or wanting below this in the valley. Near Judge Parker's estate at Esopus is an island, without name, upon which occur the most southerly specimens of the arbor vitae (Thuja occidentalis) in the aqueduct region. Near Piermont, just below Nyack, are large quantities of marsh fleabane (Pluchea camphorata), on what are locally called the "Flats." This plant is obviously an intruder from the salt marshes of the Long Island and New Jersey coasts.

Scores more of these exceptions could be cited to prove the general rule that the flora of the Catskill Aqueduct region is of two types. It is true that they intergrade somewhat, but on the whole the Highlands seem to act as a barrier to many of our wild plants, particularly to the mountain species, some of which have never been known to occur in the valley south of Storm King or Anthony's Nose. It is through the former that the aqueduct takes the great plunge under the Hudson to the east bank of the river.

THE MOUNTAIN PLANTS.

No real Alpine conditions are found in the Catskills, the highest peak being scarcely over 4,000 feet. But there are many peaks that are over 2,000 feet, and toward the summit of these, and on the top of Slide Mountain, there occurs a group of plants that are found practically nowhere else in the aqueduct tract. Some of the more conspicuous of them are:

Braun's Polystichum (Polystichum Braunii), a strong growing fern, growing in rocky woods.

Balsam Fir (Abies balsamea) the tree of fragrant memory, common enough near the head-waters of Esopus Creek, unknown in the lowlands. Wood Reed Grass (Cinna latifolia); besides the Catskills it has been found at Pine Plains, Dutchess County. Several species of sedge, which are plants with the general aspect of grass, notably Carex novaeangliac. Mountain Yellow-eyed Grass (Xyris montana), known only from the highest regions of the Catskills, in our area. Mountain Strawberry (Fragaria Canadensis), and its relative Fragaria terra-novae, both isolated on the highest peaks in the watershed of the Ashokan Reservoir.

Mountain Ash (Pyrus sitchensis), differing from the common mountain ash in its short-pointed leaves. The latter is common in many places in the valley, but P. sitchensis is found only at the highest elevations. Violet (Viola Selkirkli), known in the Catskill region, only from near mountain summilts, and usually only above 2,500 feet where another species, peculiar to high clevations, Viola renifolia, is also found. Found in the AdiOne-flowered Wintergreen (Moneses uniflora), with small white flowers in June. rondacks and nearly to the Arctic Circle, but reaching nearest to New York City in the Catskills. Canadian Blueberry (Vaccinium Canadense), a low bush not over eighteen inches tall, with leaves bright green on both sides, and nearly evergreen.

Plants of the Catskill Aqueduct Region-Continued.

885

Adoxa (Adoxa Moschatellina). remarkable because it is found in New York State only near Arkville, Delaware County, on mountains that drain into the upper portion of Ashokan Reservoir.

Large-leaved Golden Rod (Solidago macrophylla), reaching its most southerly distribution point on. the highest peaks of the Catskills, and found far northward in the Hudson Bay region.

At somewhat lower elevations, in fact nearly throughout the Catskills and in the higher elevations of the Hudson Highlands, are many other species that are rare or wanting along the lower stretches of the Hudson nearer sea-level. Among the most beautiful of these are:

Clintonia (Clintonia borealis), with yellow flowers and glossy basal leaves.

Green Orchis (Habenaria hyperborea), with spurred, irregular, greenish-white flowers.

Showy-fringed Orchid (Habenaria grandiflora), with very striking purple-fringed flowers in July.
White Adders-Mouth (Microstyles monophyllos), a sinall orchid with whitish flowers.

Coral-root (Corallorhiza trifida), a slender saprophytic orchid with whitish stems and flowers, but no

leaves.

Northern Stitchwort (Stellaria borealis), a white-flowered chickweed-like herb found on wet rocks and flowering in summer.

summer.

Mountain Sandwort (Arenaria groenlandica), making small tufts in rocky places. Flowers white, in Foam Flower (Tarella cordifolia), with beautiful white flowers in May and June, so plentiful as to suggest its common name. Found very sparingly below Peekskill, if at all.

Purple or White Avens (Geum rivale), with not very numerous flowers, and tassel-like, silky fruits. Barren Strawberry (Waldsteinia fragarioides), a strawberry-like plant with white flowers, and dry fruits. Leaves nearly evergreen. Ginseng (Panax quinquefolium), known only from Haverstraw Bay northward. Formerly much catlected for its supposed medicinal qualities, and now nearly extinct in the region.

Labrador Tea (Ledum groenlandicum), a low bog shrub with russet foliage and white flowers. Known only from Dutchess County northward. Threc-leaved Solomon's Seal (Smilacina trifolia), very rare in the Hudson Valley in Dutchess County; unknown south of it.

Twisted-Stalk (Streptopus amplexifolius), with greenish-white flowers and leaves bluisa beneath. Known only from the Catskills.

Showy Ladies' Slipper (Cypripedium reginae), the finest of all the ladies' slippers. Flowers whita, variegated with crimson stripes. From Dutchess County and northward.

Round-leaved Orchis (Habenaria orbiculata), has two large, nearly round leaves, flat on the ground. They are silvery beneath.

Rattlesnake Plantain (Epipactis tesselata), a small orchid with variegated leaves and whitish flowers on slender spikes.

Golden Seal (Hydrastis canadensis), now known only from near West Point and northward: very rare. Formerly much collected for its medicinal roots.

Anemone (Anemone riparia), known only from Dutchess County in our area.

Hepatica (Hepatica acutiloba), a pointed-leaved form of this common wild flower in the aqueduct region only from the Catskills.

Three-toothed Cinquefoil (Potentilla tridentata), a white-flowered herb with a woody base, the leaflets toothed at the end. Found only from Dutchess County and the Catskills.

Seneca Snakeroot (Polygala Senega), sometimes called mountain flax. Flowers in long, slender spikes, white, tinged with green.

Giant St. John's Wort (Hypericum Ascyron), almost a shrub, with large yellow flowers Grows in moist places, only in the Catskills in the Hudson Valley region.

Dwarf Cornel (Cornus canadense), its greenish-white bloom, suggestive of miniature dogwood, `is borne at the end of the stems, which are scarcely over four inches tall. Known now only from the Highlands northward.

Ague-weed (Gentiana quinquefolia), somewhat like the common fringed gentian, but without the fringe. Rare in northern Westchester County, and increasing northward through the Highlands to the Catskills.

Bugle-weed (Lycopus membranaceus), with the aspect of mint, but without the mint odor. Known only from the Catskill area.

Hobble-bush (Viburnum alnifolium), a shrub with showy white flowers and red fruits. Common north of the Highlands at moderate elevations and in the Catskills.

Swamp Laurel (Kalmia polifolia), a small relative of the mountain laurei which is scattered all aboug the water system. K. polifolia is a bog shrub with two-edged twigs and known only from Dutchess County northward.

Wild Rosemary (Andromeda glaucophylla), a low bog shrub with white drooping flowers and whitish foliage, known in the region only from Orange and Putnam Counties northward.

Van Brunt's Jacob's-Ladder (Polemonium Van Bruntiae), a blue showy herb found in the Catskills, but scarcely south of them in the water system.

Oswego Tea (Monarda didyma), conimonly cultivated but apparently wild only in the Catskills, so far as our region is concerned. Flower scarlet and showy.

Twin-flower (Linnaea borealis), a low-carpeting plant with twin-flowers. Rare or wanting now south of the Highlands, although there are old records of it from Long and Staten Islands.

Wood Valerian (Valeriana uliginosa), a pink or white flowered herb known only from the northern end of the Highlands northward.

Scores more of these northern species of plants could be cited, but space forbids more support of the general thesis that the Catskill water system cuts through two distinct floral regions. Many trees, such as the spruce, larch, and bur oak, and a considerable number of shrubs follow the same general distributional tendency as the herbs, their occurrence south of Peekskill being very rare or unknown The few exceptions mentioned earlier only serve to prove the rule.

THE LOWLAND PLANTS.

Of the 2,038 native flowering plants found wild within one hundred miles of the city, about 1,600 are found in the Hudson Valley and Catskill regions. Deducting those that we have seen to be of northern tendencies, there remain a large number of species that make up the great bulk of vegetation of these regions. These generally distributed plants are too numerous to mention here. Wherever the vegetation has been undisturbed, as through the Highlands, it is still a forest region with a wealth of wild flowers and ferns and shrubs as undergrowth. In spite of the wealth of plants, there appears to be no species endemie there, i. e., found nowhere else.

As illustrating the tendency of many essentially lowland plants not to grow north of the Highlands the sweet-gum (Liquidambar Styraciflua), sour gum (Nyssa sylvatica), and tulip tree (Liriodendron tulipifera), are interesting. All are common near the city and south of it. The first has never been recorded north of Peekskill, Nyssa is very rare north of the Highlands, while the Tulip Tree is unknown as a wild tree in the Catskills.

Perhaps the most beautiful of all the shrubs of the Catskill Aqueduct system is the mountain laurel (Kalmia latifolia), whose white or pinkish flowers color great areas in the Highlands and at other places.

886

The Big East River Bridges.

THE BIG EAST RIVER BRIDGES.

(For details of the big bridges not in the running text, see table.)

BROOKLYN BRIDGE.

THE tolls are: For foot passengers, free; railway fare, 3 cents, or 2 tickets for 5 cents. Roadway tolls for vehicles abolished July 18, 1911. On August 23, 1897, the bridge railway was leased to the elevated railroad companies (now operated by the Brooklyn Rapid Transit), paying therefor 10 cents per car: trolley cars, 5 cents per round trip. About 250,000 people cross the bridge in a day. Width of bridge, 86 feet. Length of each land span, 930 feet. Length of Brooklyn approach, 998 feet. Length of New York approach, 1,562 feet 6 inches. Size of Manhattan caisson, 172 x 102 feet. Size of Brooklyn caisson, 168 x 102 feet. Timber and iron in caisson, 5,253 cubic yards. Concrete in well holes, chambers, etc., 5,669 cubic feet. Weight of Manhattan caisson, about 7,000 tons. Weight of concrete filling, about 8,000 tons. Manhattan tower contains 46,945 cubic yards masonry. Brooklyn tower contains 38,214 cubic yards masonry. Depth of tower foundation below high water, Brooklyn, 45 feet. Depth of tower foundation below high water, Manhattan, 78 feet. Size of Manhattan tower at high water line, 140 x 59 feet. Size of Manhattan tower at roof course, 136 x 53 feet. Total height of towers above high water, 272 feet. Grade of roadway, 3 feet in 100 feet. Height of towers above roadway, 153 feet. Size of anchorages at base, 129 x 119 feet. Size of anchorages at top, 117 x 104 feet. Size of anchorages, 89 feet front, 85 feet rear. Weight of each anchor plate, 23 tons. Number of cables, 4. Diameter of each cable, 154 inches. Length of each single wire in cables, 3,578 feet 6 inches. Ultimate strength of each cable, 12,000 tons. Weight of wire, 11 feet per pound. Each cable contains 5,296 parallel (not twisted) galvanized steel, oil-coated wires, closely wrapped to a solid cylinder, 154 inches in diameter. Permanent weight suspended from cables, 13,820 tons.

MANHATTAN BRIDGE.

Manhattan terminal, Bowery and Canal St.; Brooklyn terminal, Nassau, near Bridge St. Width of bridge, 122 feet 6 inches. Length of each land span, 725 feet. Length of Manhattan approach, 2,067 feet. Length of Brooklyn approach, 1,868 feet. Bridge is of double-deck design, first deck has one 35-foot roadway in centre and two subway tracks on each side and one 11-foot footwalk on each side, top deck has four trolley tracks. Approximately 40,000 cubic yards excavation for each anchor pier; approximately 115,000 cubic yards masonry and concrete in each anchor pier. Height of cables at top of tower above mean high water mark, 322 feet 6 inches. Height of roadway at centre of bridge above mean high water mark, 149 feet. Grade of roadway 3% feet in 100 feet. Number of cables, four, 37 strands in each cable; 256 wires in each strand; 9,472 wires in each cable; 37,888 wires in four cables. Size of wire, 0.192 inches in diameter. Size of cable completed, 214 inches in diameter. Length of each wire, 3,223 feet 6 inches (anchor to anchor). Ultimate strength of each cable, 26,600 tons. Weight of steel in cables and suspenders, 7,800 tons. Weight of steel in other parts main bridge, 33,900 tons. Weight of steel in approaches, 18,300 tons. East footwalk opened to pedestrians July 18, 1910. West footwalk opened May 11, 1911.

WILLIAMSBURG BRIDGE.

The tower foundations for the bridge in Manhattan are at the foot of Delancey Street, and in Brooklyn at a point between South Fifth and South Sixth Streets. The bridge ends at Clinton Street in Manhattan, and at Havemeyer Street in Brooklyn. Construction commenced November 7, 1896. Size of Manhattan caissons (2), 76 x 60 feet; Brooklyn caissons (2), 79 x 63 feet. Depth of tower foundations in Manhattan, north caisson 55 feet, south caisson 66 feet below mean high water; in Brooklyn, north caisson 107 feet 5 inches, south caisson 91 feet 9 inches below mean high water. Height of masonry in Manhattan and Brooklyn towers, 23 feet above mean high water. Total height of towers above mean high water, 332 feet 9 inches. Size of both anchorages at top, 149 feet x 127 feet 5 inches. Length of each side span, 596 feet 6 inches; Manhattan approach, 2,650 feet; Brooklyn approach, 1,865 feet. Width over all, 118 feet. Two roadways, each 20 feet wide, two footwalks, each 17 feet 8 inches wide. Height of roadways at towers, 125 feet 8 inches above mean high water. Height of roadways at centre of bridge, 145 feet 6 inches above mean high water. Number of supporting cables, 4. Diameter of each cable, 18% inches. Length of each single wire in cables, 2,985 feet. Total length of wire in four cables, 17,404 miles, Weight of four cables, including suspenders, 4,900 tons. Weight of structural steel and iron in main bridge, 26,300 tons; in approaches, 16,600 tons; total, 47,800 tons. Surface railway for Brooklyn lines began operation November 3. 1904. Surface railway for Manhattan lines began operation February 9, 1905. Elevated railway began operation September 16, 1908. QUEENSBORO BRIDGE.

Plans approved by the War Department, February 23, 1901. Main bridge is a continuous cantilever. Bridge, with approaches, extends from Second Avenue, between 59th and 60th Streets, Manhattan, to Crescent Street, Queens. Construction commenced June, 1901. Height of highest masonry piers, 124 feet above mean high water. Length of Manhattan approach, 1,052 feet; west channel span, 1,182 feet; island span, 630 feet; east channel span, 984 feet; length of Queens approach, 2,672 feet 6 inches. Queens plaza has a length of 1,152 feet, from Crescent Street to Jackson Avenue. Width over all, 89 feet 6 inches. Width of roadway, 52 feet 3 inches. Two sidewalks, each 16 feet wide. Height of roadway in central portion of bridge, 143 feet above mean high water. Height of footwalks in central portion of bridge, 165 feet above mean high water. Height of lower balconies on towers on Blackwell's Island, 202 feet 6 inches above mean high water. Height of upper balconies on towers on Blackwell's Island, 333 feet above mean high water. Weight of steel and iron in main bridge, 52,600 tons; in approaches, 20,066 tons. Total, 72,666 tons. Bridge opened for pedestrians and vehicles, March 30, 1909. Surface railway began operation September 19, 1909.

HELL GATE ARCH BRIDGE,

The bridge spans the East River at Hell Gate, between Ward's Island and Astoria, Long Island. Designed and built by Gustav Lindenthal for the New York Connecting Railroad to connect the Pennsylvania and New York, New Haven systems. It is the longest arch in the world. The upper chord of the arch is 300 feet above mean high water at the centre and 180 feet at the ends of the span; the lower chord is The arch carries four railway tracks 260 feet above mean high water at the centre and 40 feet at the ends. It is the heaviest bridge in the world, weighing (two passenger and two freight) on a solid concrete deck. 52,000 pounds per lineal foot and carrying a loading of 24,000 pounds per lineal foot, making a total carrying capacity of 76,000 pounds per lineal foot. The steel work weighs 19,000 tens and the flooring and track weigh 7,000 tons. The heaviest single member weighs 185 tons and has a cross section of 1,384 square inches. The width of the bridge is 93 feet between railings and 60 feet between centres of trusses. Long Island tower is 104 x 140 feet at the base and is founded on rock in open cut at 20 feet depth. Ward's Island tower is 119 x 140 feet at the base and rests on 21 pneumatic concrete caissons, founded on Total concrete rock varying from 58 to 120 feet below the ground surface. Height of towers, 240 feet. in towers, 110,000 cubic yards. Total concrete in bridge towers and approaches, 500,000 cubic yards. Construction of arch commenced November, 1914. Arch was erected by cantilevering out from the towers, The two halves were each half being held by connection to temporary backstays built behind the towers. joined October 1, 1915. Entire steel work completed January, 1916.

The
The