The Brooklyn Daily Eagle from Brooklyn, New York • Page 26

THE BROOKLYN DAILY EAGLE. NEW YORK. THURSDAY'. JANUARY 0. 1908.

TUNNEL EQUIPMENT IN WORLD; CONSTRUCTION OF THE TUNNEL PRESENTED DIFFICULT PROBLEMS. STATISTICS OF, EAST RIVER TUNNEL. NOVEL DEVICES TO PREVENT ACCIDENTS Divergent Character of Strata Through Which the Tubes Were Cut tunnel was in rock and there was no shield tho same arrangement was used and the lining kept generally close to the bench. As the lining was erected it was grouted externally through a Hi inch hole in each Begment, closed with a plug. In the rock the space outside the lining was hand-packed with stone spalls before being grouted, and the grout was confined in sections by concrete bulkheads or dams built In this space at intervals.

The grout consisted of equal parts of crusher dust and cement, fed in at the top and mixed in an inclosed cylinder with revolving paddles, operated by a small air engine. When sufficiently mixed air pressure was applied at the top and the Total Length of Cast Iron, 'North Tube7 6,747 feet. Total Length of Cast Iron, South Tube 6,766 feet Total Weight of Cast Iron Rings, North 14,530 tons Total Weight of Cast Iron Rings, South Tube. 14,878 tons Reinforced Section, North Tube 2,218 feet Reinforced Section, South Tube 2,339 feet Ground Broken. Battery Park, Manhattan, March 4, 1903.

Excavation for Shaft of Both Tubes Begun. Joralemon Street, Brooklyn, July 10, 1903. Power Supplied from Big Plant in Manhattan, Which Has the Greatest Single Exhibit of Steam Driven Electrical Generators in the World, and Transformed in Brooklyn Sub-Station Special Apparatus and Arrangements to Guard Against Accidents Supplement a Complete Block System Two Ventilating Shafts Precautions Against Leaks and Fire. Made the Task Seem Almost Impossible of Accomplishment Division Engineer Noble Gives the History of the Construction Work from an Engineering Standpoint Quicksand at Unexpected Places Made it Necessary to Reconstruct Several Portions of the Tunnel. Excavation for North Tube Shaft.

Near Henry Street, Brooklyn. Begun July 10, 1903. is generally admitted that the HE equipment of the East River tunnel and that part of the Interborough subway system in Brooklyn, from tho Borough construction of the two tubes constituting the East River tunnel presented engineering problems of unusual difficulty mi grout was forced through the plug holes and behind the lining by means of a connecting rubber hose. The lining was made watertight by calking with metallic lead in the recesses at the inner edges of the joints and grom-meting with bolts under the heads and nuts with a ring of hemp and red lead under a plate washer. Reconstruction Made Necessary.

Deviations from the established grade were caused by the faulty control of the Brooklyn shields In many places between to the surface, run out on a trestle leading to a dock west of the United States Barge ollice, and there dumped into scows. The headings for the norlh and south tubes were started east from the Manhattan shaft on April 9 and April 16, re-specti ely. By the end ot May, 1906, the headings reached a point near the end of the rock, where further progress was stopped temporarily to install shields. In September the advance was resumed Hall to the Long Island depot, at Flatbush and Atlantic in fact, problems that had never before been encountered in similar undertakings. This was largely brought about by the divergent character of the strata no expense was spared and every known engineering expedient was adopted to create a plant of maximum permanency and reliability and the result Is a power station which Is nowhere rivalled by any engineering work of a similar character.

The present equipment of the plant represents In engine capacity, at normal rating, approximately power, which, if necessary, could be increased to power. Space is provided, within the structure, for an additional generating equipment of from 20,000 to power. Greatest Single Exhibit of Steam-Driven Electrical Generators, in World. The operating room, which forms the northerly section of the power house, forms undoubtedly the greatest single exhibit of steam-driven electrical grenerat-ors In the world. Here are seen the nine 6,000 kilowatt alternators, each driver) by a power engine.

Between the sixth and seventh engine room the Henry street shafts and the reef. These necessitated subsequent reconstruction of parts of the tunnel, especially in the north tube, to avoid too great an irregularity in the resulting grades, and this was successfully accomplished without materially interfering with the regular work of finishing the tunnel. with the new shields. The first Brooklyn shafts, one for each tube, were located in Joralemon street, about 1,300 feet inland from the river, just west of Henry street, and about 700 feet from the end of the tunnel section. Excavation of the south shaft began April 16.

1WS, and for the north shaft June 10, 1903. They were each 20 feet by 21 feet in plan, sheeted and extended 65 feet below the surface, to the bottom of the tunnel. The first portion of the tunnel to be -avenues, may be said to be practically identical with that of the Manhattan subway. With slight variations the rails and electrical equipment are the same; the cars are those which have been run through the Manhattan subway since it was opened, with the addition of new cars to be operated from time to time as they are received from' the. factories, and the power is furnished from the main plant of the, Interborough Company at Fifty-ninth street, and.

is converted the third rail in the tunnel and in the Brooklyn extension through the new Brooklyn sub-station, situated on Willow place. There are' however, Installed In the tunnel tubes; a number. of safety devices of unusual" design and these form the chief divergence in equipmnt from, that of the subway in Manhattan. All sections Excavation for South Tube Shaft. Near Henry Street, Brooklyn.

Begun March 23, 1903. First Ring Erected. North Tube, Manhattan, August 2, 1903. South Tube, Manhattan, July 23, 1903. North Tube, Brooklyn, September 15, 1903.

South Tube, Brooklyn, July 10, 1903. Last Ring Erected. North Tube, Manhattan, February 8, 1907. South Tube, Manhattan, April 12, 1907. North Tube, Brooklyn, February 6, 1907.

South Tube, Brooklyn, April 11, 1907. Manhattan and Brooklyn Shields Met. North Tube, December 15, 1906. South Tube, March 1907. Reconstruction Begun.

North Tube, June 26, 1906., South Tube, April 5, Reconstruction North Tube, August 17, 1907. South Tube, June 12, 1907. Pile Driving Begun. North Tube, April 30, 1907. South Tube, March 11, 1907.

Pile Driving Completed. North Tube, July 19, 1907. South Tube, July 25, 1907. Reinforcement Begun. North Tube, August 25, 1907.

South Tube, August 30, 1907. Reinforcement Completed. North Tube, November 6, 1907. South Tube, November 13, 1907. The method adopted was simple and I consisted generally of removing the cast- iron segments in the lower half of tne through which the tubes were cut.

Quicksand was discovered at many unexpected places, and this resulted in the necessity both for reconstructing certain portions of the tubes and for providing additional support by the means of piles where the construction Itself was not replaced. This reinforcement of the tubes is what led to the assumption at one time that the tunnel might never reach completion, but the engineers met each new difficulty as it arose with a new resource, and the final result was complete success. No lees than fifteen lives were sacrificed during the big operation, most of them being workmen who collapsed fro the "bends," but the loss of life was considerably below the aver- in most undertakings of similar magnitude. There was no accident of large proportions resulting in the death of a number of men simultaneously, but nearly built in Brooklyn was the length of abou 700 feet in each tube east from the shafts to the end of the section. The shield for the south tube was started east July 10, 1003, and reached the end of the section January 11, 1004.

The shield for the north tube was started east September 15, 190.3, and reached the end of the section January 16. 1904. The shields for the west headings were being equipped while the first pair progressed east. The south shield began the advance west from the shaft November 12, 190,3, and the north shield Feb I tunnel section and replacing them with new segments, curved to an elliptical outline so as to give more interior space at the bottom. For a short stretch in each tube near Hicks street, where the earliest and most marked variations occurred, the upper half of the tunnel lining was forced outward and upward by heavy hydraulic pressure sufficiently far into the surrounding soil to p'ermlt the construction of a new masonry roof, providing increased clearance.

The total length of tunnel reconstructed is 2,919 feet, of which 1,957 feet were in the north tube and 962 feet in the south tube. The time occupied by the work was thirteen months. I Files Sunk for Additional Support. The matter of the stability of the fine sand each side of the Brooklyn reef under the loads of moving trains AUGUST BELMONT, Ventilating Shafts. Battery Park, Mantiattan; aeptn is teet.

58 Joralemon Street, Brooklyn; depth, 62 feet. First Train Run. NovAnber 27, 1907. Through North Tube, from Bowling Green to Borough Hall, Brooklyn. First Train Through Both Tubes.

January 6, 1908. Regular Service Inaugurated. 1 January 9, 1908. ruary 2, 1904. After the bulkhead lme was passed caissons were sunk for the new shafts just west of Furman street, and these were put into use in April, 1905, while the original shafts were filled up.

The new shafts each measure 9 feet by 13 feet in plan, and were sunk 30 feet below the surface to the top ot the tubes, to which they were then connected. The final meeting between the headings took place between the two rock formations under the river. The north shields met December 14, 1906. and the south shields met March 1, 19C7. They were then dismantled, leaving the outer shells in place, after which the cast iron lining was completed.

Material removed from the tunnel through the Furman and Henry street shafts was hoisted to the surface by melns of a lift, with which each shaft was provided, dumped into overhead bins, discharging at the bottom Into carts to every casualty may be attributed to the' workmen entering the tubes when they were not in fit physical condition. Some of the men would drink upon completing their- day's work, and then would enter the tunnel the following day unable to labor under the heavy air pressure requisite for the task. A complete history of the construction of the East River tunnel from the beginning; has been furnished to the Eagle by Frederick C. Noble, who first was division engineer, under the old Rapid Transit Commission, and who is the present division engineer of the Public Service Commission. Mr.

Noble's story of the undertaking, from an engineering" viewpoint, is as follows: of the Tunnel Construction by Frederick C. Noble. The tunnel under the East River, from South Ferry, Manhattan, to Joralemon street, Brooklyn, is part of the Brooklyn extension of the original subway in Mau- having been questioned by officials of the Interborough Company, it was considered advisable by them to provide some auxiliary means of support such as piles reaching to rock at intervals under the tubes where they passed through the material in question, his view was not concurred in by the city engineers, but as experiments showed that the piles might be driven rapidly, without materially delaying completion, the work was allowed to proceed. In the midriver section between the Brooklyn reef and the Manhattan rock POTENTIAL FUTURE POSSIBILITIES THROUGH PROJECTED SUBWAY SYSTEMS. formation seventeen concrete pile bents 1 Extension to Flatbush avenue depot expected to be ready by March 1.1 be teamed away.

Tunneling Methods. All tunneling operations were carrieJ on in compressed air, except in the Brooklyn headings, east of the Henry street shafts, where the tubes are above water level, and inside the bulkhead line at South Ferry, where the leakage could were sunk under the north tube and fifteen under the south. Each bent consists of two piles, about twenty IncheB in diameter, spaced 7 feet apart transversely and about 30 feet apart longitudinally of the tunnel. The piles were driven to depths ranging from 5 to 40 feet. In the fine sand formation east of the Brooklyn reef fifteen similar pile bents were sunk in each of the tubes.

The pile bents in this section were spaced about 50 feet apart longitudinally, and nattan and Is known as Contract No. 2. The contract for the construction was let by the city to the Rapid Transit Subway Provisions made for future underground roads Five levels of railroads, one on top of the other, at Flatbush avenue and Fulton street Fourth avenue route probably the next work to be -undertaken Difficulties encountered in constructing the subway along Fulton street. construction Company, as general con tractor, Septamber 11. 1902.

The tunnel pumping, me section was later sublet to the New York pounds to a maximum of forty-two continuously a sub-subway crossing, un Is hopefully anticipated that the cnkjre Brooklyn extension ot the subway system to the derneath the other tracks of the main line, to. make connection for future extensions, the one from lower Fulton street and the one from Manhattan Long Island depot at Flatbush and Rtlantic avenues, now in extended to depths ranging from a few feet to 75 feet. In every case the piles were driven to hard material. To drive the plies it was necessary to remove the bottom plates of three rings below the spring line. The piles were then forced down by hydraulic jaoking In sections, with an outer steel casing filled with concrete, reinforced by six longitudinal rods.

A 4-inch pipe ran through the interior of the pile, and through this pipe a smaller one jetted at the end. When a firm bearing was reached the piles were connected at the top by a broad reinforced concrete cradle, and the castiroa lining replaced. Who Financed the Tunnel Enterprise. course of construction, will be ready for operation by March 1. Those in charge of the construction of the uncompleted portions of the Brooklyn subway, from the Borough Hall to Atlantic avenue, as well as the officers of the Interborough Rapid Transit Company, in their public statements, have set a somewhat later date than this for the running of trains through to the Long Island Railroad depot.

but in private these men have expressed their conviction that by March 1 the entire subway will be operated with a full passenger service from Manhattan and the Bronx to Atlantic avenue, this borough. The several disappointments that followed the early announcements of the date for the opening of the tunnel have Bridge to an extension up Lafayette avenue, and another connecting with an extension through Fourth avenue. To build the latter the Greene avenue-Hanson place storm sewer, which has an inside diameter of fifteen feet, had to be moved bodily out of the To accomplish this work the building3 along the south side of Flatbush avenue and Fulton street within these lines are in many instances, placed on new foundations, which extend forty-four feet below the level of the sidewalks, and the elevated railroad was temporarily supported on frames, which, at the corner of Fulton street and Flatbush avenue, were eighty-five feet in height, at which point there are to-day five levels of railroads, one on top1 of the other, the bottom' of one of which was constructed last. The total length of the structure of this section of thes subway Is 5,770 feet, and the length of track Is 24,500 feet. The of the completed system for interbor-( alternators are located, three horizontal ough communication have blocks and sig nal devices, but besides these th East River Tunnel has a complete system of its own for precaution again accidents, believed to be move elaborate than any provisiens of the kind hitherto installed on a transportation line.

These special devices, which will be found described in detail below, have attracted the attention and interest of all railroad men. Interior Lining of Concrete. After making the castiron lining watertight, the air pressure was removed, and the interior of the shell lined with small stone concrete. At the bottom, under the track, the concrete is brought 8 inches inside the flanges and leveled at the ends of the ties to afford them a solid bearing. A concrete bench is built at each side of the track to inclose the seven single-way ducts in each bench for electric cablt'3.

At intervals of three hundred feet, the duct bench is omitted for a space of ten feet, to leave a chamber for splicing the cables, and these are covered with iron grating3. The concrete lining of the roof is brought flush with the inside of the f.anges of the cast iron lining wherever Ihe tunnel is in rock, or under the land cast of the bulkhead line in Brooklyn. made both the contractors for this sec tion, Cranford and McNamee, as well as the operating officials, reticent regarding the date of completion, as they are It probably is best to begin a de kilowatt power turbo-alternators, with space provided for a fourth, in case this shall ever bo required. The large engine-driven traction alternators supply the electrical energy required to operate the car equipment, while the turbo-alternators supply the electricity needed for the lighting of the subway, including that of the passenger stations. The supply of electricity for the fixed lights within the whole subway system is independent of the supply of electricity to the cars, except, in an emergency, when the lighting current could be taken from the traction alternators.

The power required to drive the several alternators within this power house is converted into electricity at 11,000 volts potential. This electricity is then transmitted through high potential cables to the seven sub-stations in the boroughs of Manhattan and the Bronx, and to the recently completed sub-station at 27-31 Willow place, Brooklyn, for tho operation of the Brooxlyn extension. desirous that in this instance no premature announcements be made. scription of the equipment of the tunnel and Brooklyn subway with an ac count of how the power is furnished. Power for Brooklyn Subway Exten sion Main Power House and Willow Place Sub-station.

pounds to the square inch above atmospheric pressure at. the deepest section under the middle of the river. The tubes were divided into working chambers by brick or concrete bulkheads at intervals, into each of which were built two locks for the passage of workmen and materials. In the soft material the tunneling was by shield, under the protection of which the castiron lining was erected. There were, six shields, one for each of the four headings from Henry street shafts and one in each of the Manhattan headings, which were set up In shield chambers when these headings had reached the end of the rock formation.

Enough material was removed at one time to permit the shield to be forced ahead by hydraulic pressure so that one ring could be erected, after which the operation was repeated. Breast boards were used against, the face were the material showed a tendency run or slough off. In the fine sand a water jet was used to soften the material in the lower part of the face, permitting it to be blown out of the working chamber through a discharge pipe bv the tunnel pressure. On the Manhattan side, where the material was rock, excavation was made in two stages by the ordinary top-heading and beach method. Where the rock was of good quality and sufficiently thick overhead, no roof timbering was necessary, and the heading was carried a considerable distance ahead of the bench.

Otherwise roof timbering was resorted to. Where the sh'elds encountered rock on the Brooklvn side, they were slid through it. while the excavation was carried well ahead of the sh'eld wherever possible by a bottom heading. The overhang was then drilled and blasted down from the shield as It advanced. Material of Tunnel Shell.

The tunnel shell is built up of flanged castiron plates bolted together by their flanges to form rings, each composed of eight segments and a key. The rings are 13 feet inches internal diameter, 22 inches in length. lVs inch minimum thickness of metal and 7 inches to iy2 inches depth over flanges. All abutting surfaces are planed, the segments are bolted to the adjoining ones in the same ring with three one-Inch bolts, and the rings are bolted to each other with forty-nine one Inch bolts in the circumferential flanges. The weight of the ring varies according to location, the lighter ones, weighing 7,310 pounds each, being used in rock and above the water level in Brooklyn, and the heavier ones, weighing 8,332 pounds and 9,410 pounds each, being, used under the river and for the rest of the work.

Many of the segments, both of the light and heavy sections, cracked under the strains they were subjected to during construction, and these were removed if practicable, or, if not, they were reinforced later, with steel rods imbedded In concrete. The castiron segments were lifted and For the remaining distance in soft material under th river the concrete. lining Tunnel Company. Beginning at a point in Battery Park, near South Ferry, about 400 feet from the bulkhead line, the line of the iunm'I runs under the feivy houses, crosses the river Jo the foot of Joralemon street, Brooklyn, and continues up Joralemon street as far as Clinton street, a total distance of 6,790 feet. In turning from the river on the Brooklyn side to take the direction of Joralemon street the tunnel line is on a curve of 4,500 feet radius through an arc of-about 27 degrees.

'The grade is 3.1 per cent, downward on each side toward the river, except for a short distance near the middle, where the grade is Vi per cent. This portion is joined to the steeper grades on each side by vertical curves of 10.000 feet radius. The tunnel is everywhere below water level, except for 700 feet at the Brooklyn end. The lowest point reached by the tunnel is 94 feet below mean high water. The tunnel consists of two circular single track tubes of the usual cast iron ring construction.

They are 15 feet 6 inches internal diameter, and run side by side 28 feet apart on centers, except under Joralemon street, where this distance is decreased to 26 feet. The tubes are lined throughout with concrete and are grouted externally. Tubes Cut Through Bock and Quicksand. The material through which the tunnel was, cut, on the Manhattan side, from the shaft east to the lowest point of the tunnel, a distance of about 2.700 feet, consisted almost entirely of rock. About half way from the low point to the Brooklyn side another stretch of rock, about 400 feet in length, was passed through.

This formation is supposed to be continuous with Coenties Reef, farther north. The rock was generally found to be a good character of mica schist or gneiss, and, except in places where the rock covering was slight or larking, no timbering was required. For the remaining distance the material consisted generally of sand of varying degrees of fineness. Under Joralemon street and part way out in the slip between piers 17 and IS the sand was of ordinary coarseness and contained con-siderabie gravel together with cobbles and bowlders of all r.izes. Between the two rock formations and east or; the Brooklyn reef the sand was found to be extremely line and ofton contained a certain admixture of clay.

This material Is of the same nature as the quicksand encountered In foundations in the lower of Manhattan Island, and shows a similar marked tendency to run, whenever distubd. Commencement of the Work. Excavation for the Manhattan shaft, located in the Battery Park inclosure, opposite South Ferry, began March 4, 1903. The shaft measures 14 feel by 52 feet in plan, taking in the headings of both tubes, and extends to the tunnel sub-grade, about 45 feet below -the surface. It was sheeted on all sides with five-inch tongued and grooved sheeting, driven to the rock line, which was leached approximately half way dow n.

As in the case of the entire Manhat is made sufficiently thick to cover the flanges three inches at the top quarter points, and further increased in thickness tan subway the Brooklyn extension is operated by electricity generated, at the main power house, located on the block bounded by Eleventh avenue, West Fifty-eighth street, Twelfth avenue and West Fifty-ninth street, Manhattan. This power house, therefore, furnishes the whole amount of electrical energy re at the crown and spring line on each side by making the outline flat at these iilaces. The whole reinforcement adds greatly to the resistance of the tunnel section to deformation. After the concrete lining was placed it was given a wash of cement grout as a finish to the surface. excavations totalled 370,000 cilblcyards; the concrete Amounts to 75,000 cubic yards, and the steel and iron used -weighs 9,000 tons.

The contract, price" for this section was $4,200,000. Potential Future Possibilities. The promise for the future contained in the comprehensive provisions for extensions to other lines, in the completion of the present subway as far ds Atlantic avenue, and in the ultimate possibilities growing out of the beginning so satisfactorily made are such as to almost exceed in import that much ot realization comprised in the operation of the tunnel itself. There can bo little doubt but that eventually all of the depressed connections' for future subway routes will be utilized, and that not only these, but many other present unplanned, will grow out of the commencement that has been made. The Fourth Avenue Subway, which, in probability, will be the next route upon which work will be started, probably will form the first connection to be made with the Brooklyn extension of the Interborough system.

Assurance is also forthcoming that every effort will be made to. have the plan providing for a continuance of the present subway beyond Atlantic avenue to the Willlnk entrance, at Prospect Park approved; a connection will undoubtedly rapidly follow with the Manhattan Bridge, and it is unlikely that the advocates of the Lafayette avenue-Broadway route will long permit this plan to languish. Current Transformed at Brooklyn Sub-station. In all these sub-stations the high potential alternating current Is transformed Into a comparatively low potential direct current at 600 volts, and at this potential the current is then conveyed from the sub-stations to the "third rails," through quired to operate the entire municipal subway as thus far' constructed in the boroughs of Manhattan, the Bronx and Brooklyn. It Is safe to say that this a system of feeder cables for distribu- generating station outranks all other tion along tne route of the subway.

power houses in its magnitude, output of All the Manhattan and Bronx sub-sta- The section now under construction runs from Joralemon street into Fulton street, thence to Flatbush avenue and along this street to Atlantic avenue, where the end of the route, as at present laid out, is reached. Changes from the original plans for this section contributed largely to the delay in its completion, as from a two and three track subway the plans were altered to include four tracks upon Fulton street and six upon Flatbush avenue, together with depressed track spurs for future connection with additional subway routes. The stations beyond Borough Hall are situated at Hoyt street, Nevins. street and finally at Atlantic avenue, where, although no physical connection with the Long Island Railroad subway and elevated train Jamaica and other Long Island points has been made, the route comes to an end practically at the station of the latter system. Provisions for Future Subways.

The depressed track spurs for connection with future subways show how far-sighted were the designers of the Brooklyn subwav system. These depressions cost an additional $1,000,000, at least, beyond the original estimate for section three, as the Brooklyn extension from Borough Hall on is officially named. These depressed track spurs are situated just east of the Borough Hall station, where arrangements fo connection with a subway to tap lower Fulton street and extend to the Brooklyn Bridge are provided; at Fulton street and Flat bush avenue, where similar facilities for a subway to the Manhattan Bridge have been installed; at Lafayette avenue, providing for the extension of tne subway system to include the Lafayette avenue-Broadway route that has been projected; at Fourth, avenue, where a connection with the Fourth avenue subway has been made possible, and at Atlantic avenue where provision for the continuance of the present subway through to the Willlnk entrance of Prospect Park will be made. power and in. the general elegance and completeness, of its constructive design.

The main power station building is 692 feet long by 200, feet wide, and, by reason of its size and the ornate design of its exterior. Is one of the architectural features of New York City. In the construction of this power house tlons are similar as to the dimensions of 1 the buildings and as to the arrangement of the electrical equipment, which uniformity insures ease and reliability of operation. The site of the Brooklyn extension is ten feet wider than the 50-foot average width of the previously constructed substations, and the building is 60 feet wide by 100 feet deep. By reason of the increase of (width', a variation in the structural plan of tho building has been adopted, which has resulted in a design that Is rendered eminently satisfactory in the matter of light, ventilation and general convenience with respect to operation.

The arrangement of the machinery and of the electrical connections is almost identical with that applying to the original sub-stations, except as to the location of the main controlling gallery, which, in this case, has been lowered for more convenient access to tha SUBWAY AS FAR AS COMPLETED. Draining and Ventilation Arrangements. Sumps for collecting the drainage of the tunnel are excavated in concrete-lined cross-passages, between the tubes, at three places under the river. One sump is located at the low grade point near the end of the Manhattan rock formation, one about half-way from there, to the Manhattan shaft, and one in the Brooklyn reef. Each sump is equipped with a Cameron single-acting pump, operated by compressed air, discharging through two six-Inch castiron drain pipes imbedded in the concrete under the track in each tube, to be the permanent shafts on ench side of the river, from which point tho water will be raised to the sewer by cimilar pumps of a larger capacity.

There are two permanent shafts, one at South Ferry and one at Willow place. Brooklyn, which serve as ventilating openings as well as connections for the drainage system and power cables. The working shaft at South Ferry was enlarged for this purpose, while the Willow place shaft was a new one. excavated under air pressure and sealed to the outside of the tunnel shell. The shafts are lined with reinforced concrete, Include both tubes of the tunnel, and measure about 14 feet by 45 feet inside in pjan.

The shafts are equipped with fans electrically operated and so arranged that the air may be moved in or out of either of the tubes. Under ordinary conditions it is expected lhat adequate ventilation will be obtained by it jvement of air from the passage swung into position for bolting up by means of a counterweighted radial arm The shaft was equipped with two lifts, one -for each heading, onernied by a 1 attached to the platform behind the shield single-drum hoisting engine with a con-1 and operated by a small air engine tinuous cable-. Tunnel, spoil was hol8tedl mounted on the platform. Where the Construction of Brooklyn Section iyt -yr? CUTTING THROUGH THE ROCK IN WHICH THE TUBE WAS LAID 1 I JfTiRJ-v From Borough Hall. On April 1.

1904, work was started on Flatbush avenue and continued without interruption until about January 1, 1905. when the agitation to increase the plan of this work from a two and three track subway to a four, five and six track subway reached such proportions that the manufacture of the steel was stopped. a new contract was entered into on swum Tff ,.4. Jiqrr Jj operating room floor. The Brooklyn sub-station is constructed entirely of masonry and steel, with the entire exclusion of all combustible material.

In the design of tho facade the object has been to create an attractive exterior consistent alike with the probable future demands of the location and with the purposes for which the building is intended. The facade includes tho employment of a granite water table, an amount of pressed Roman brick, together with various members of limestone and terra-cotta. It can be stated that no other city possesses an equipment for the generation and distribution of electric power for traction purposes comparable with this one in its magnitude and in the durability and efficiency of its various mechanical and electrical features. L. B.

Stillwell, electrical director of the Interborough Rapid Transit Company, Is responsible for the general design of the electrical work relating to the power house and substation construction, as K'-'ll as the distributing system. John Van Vleck, former mechanical engineer of the Interborough, Is responsible lor the general design of the building and mechanical equipment of the power house and sub-stations, acting also as general architect. The Safety Devices. Several new Ideas in equipment, involving a series of unique safety devices and other special apparatus are installed In the section of the subway forming the tunnel under the East River between Bowling Green and Borough Hall, Brooklyn. These devices arc destined to partially revolutionize tho handling of traffic la subway system, it is believed by the ex- Continued on Page 5.

of through tne tubes. Track Construction and Air Supply. The rails weigh 100 pounds per yard, and are spiked with tie plates to 6 inches by 8 inches yellow pine ties, spaced 18 inches centers. The ends of the ties bear on the concrete lining, and the spaces between their ends are filled with concrT.e flush with the top. The rest of the sace between and under he ties is filled w'th 2 inch broken stone ballast.

The air supply for maintaining the pressure in the headings and operating drills, pumps and hoists, was furnished by a plant on each side the river. In the early part of the work the plant proved entirely inadequate for the necessary supply and had to be greatly increased. As a result there were con 4- IE, TV September 8, 1905, providing for these greater facilities, and the first steel for the new contract was delivered in November, 1.91)5, making a delay of over ten months on this work. Under the new contract the subway on Fulton street and Flatbush avenue extends, in the stations, from building to building, and, between the stations, from the middle of the sidewalk on one side of the street to the middle of the sidewalk on the other side. This necessitates the support of the elevated, street and surface railroads on stilts, and further necessitating the underpinning of thousands of feet of buildings.

This work will be finished to Atlantic avenue, ready for the operation of trains, within several months. It has taken four years to complete it. As there are approximately 25,000 feet of single track on this section of the work, it shows a progress of 20', feet of single track subway per day, making no allowance for the delay of ten months previously noted. Five Levels of Railroads. There is one section of the work that is of especial interest, extending from Fulton and Bond streets, through Fulton street and Flatbush ave.

to Atlantic avenue. Throughout this distance there are five and six tracks, one of which is siderable periods when only one tube could be worked at a time. The Manhattan plant, located in the inclosure at South Ferry, consisted of two large and two small machines with i combined capacity of 10.000 cubic feet 'ree air per minute. The Brooklyn plant. O'-aied on Furman street, just north of ihe shafts, consisted of five large and five small machines with a combined capacity of 22,000 cubic feet free air per minute, i View of the Underground Soad at Flatbush Avenue and State Street.

View of One of the Inst Pieces of Work in the Tunnel. I i if.