1925 Public Works Department Annual Report.

Sydney Harbour Bridge.

        REPORT FOR THE TWO YEARS—1ST JULY, 1923, TO 30TH JUNE. 1925.

    I have the honor to submit the following report on the work of this branch for the two years — 1st July, 1923, to 30th June, 1925 :—

    1. WORK INCLUDED IN BRIDGE ACT.

    The Enabling Act, No. 28, 1922, provided for the construction of a cantilever or an arch bridge across Sydney Harbour, with roadway and railway approaches thereto, the railway approaches connecting with the City Railway at Wynyard-square Station and extending to the Milson's Point Railway, at Bay-road Station, the roadway approaches commencing at Grosvenor-street on the City side and extending to Junction-street at its intersection with Alfred-street on the North Sydney side.

    The bridge to provide for four lines of heavy electric railway traffic, a roadway 57 feet wide in the clear between kerbs, and two footways each 10 feet wide. The headway under the bridge for shipping to be 170 feet at high water.

    2. TENDERS.

    Plans and specifications had been prepared by the Chief Engineer, and tenders called, to close on 30th November. 1923, for a cantilever and an arch bridge having a main span of 1,650 feet without piers in the fairway, together with five steel girder spans on either .side of the harbour in approach to the main span, the total length of bridge being 3,770 feet.

    On 7th October, 1923, a cable was received from the Canadian Bridge Company stating that their firm would tender if the time was extended for thirty days, and representations had previously been made for an extension of time by the firms associated with Goninan & Co. of Newcastle. On 8th October, 1923, Mr. A. Goninan, on behalf of himself and the firms associated with him, asked for an extension of time until 14th January, 1924, or the end of January.

    The Minister approved of tenders being extended to 16th January, 1924, and all firms were so notified by cable or telegram. I wish to place on record that the firm of Dorman, Long & Co. did not at any time ask for an extension of time.

    On 16th January, 1924, tenders were opened in the Minister's room. Six firms submitted twenty tenders, viz.

Sir Wm. Arrol & Co., Glasgow, in conjunction with Sir John Wolfe Barry & Co., London.               Two tenders.
Represented in Sydney by Sir John Hunter, K.B.E., and Mr. W. A . Hutchinson, directors of Sir Wm, Arrol & Co., and Mr. E. Crutwell, senior partner of Sir John Wolfe Barry & Co.

Dorman, Long & Co., Middlesbrough and Sydney.                                                                  Seven tenders.
Represented in Sydney by Mr. L. Ennis.

Canadian Bridge Company, Walkerville, Ontario.                                                                Two tenders.
Represented in Sydney by Mr. L. A . Paddock, Dr. G. F. Porter, and Mr. E. C. G. Larsson.

McClintic Marshall Products Company, New York.                                                                Five tenders.
Represented in Sydney by Mr. Jonathan Jones.

English Electric Company of Australia, Ltd., Sydney.                                                          Three tenders.
Dr. D. B. Steinman of New York visited Sydney and was associated with this firm's tenders.

The Goninan Bridge Corporation, Newcastle.                                                                     One tender.
Mr. V. Kerihuel of the Baume Marpent Company of Belgium was associated with this tender.

    These tenders were submitted to me by the Minister for investigation and report, and on 16th February. I submitted my report to the Under Secretary, recommending the acceptance of the tender of Dorman, Long & Co. for a two-hinged arch bridge in conformity with the departmental plans and specifications, the tendered cost being ￡4,217,721 11s. 10d.

    3. THE TENDER ACCEPTED.

    The accepted tender provides for the construction and erection of a two-hinged arch bridge from Dawes' Point to Milson's Point of 1,650 feet span centre to centre of bearings, with five deck approach spans on either side of the harbour. The overall length of the bridge is 3,770 feet.

    The main arches are set in vertical planes, and are spaced 98 ft. 6 in. apart centre to centre with parabolic lower chords, having a rise of 350 feet. At the centre the arch is 60 feet deep, increasing to 192 feet over the main bearings. The abutment towers and pylons and piers of approach spans are to be constructed of granite concrete faced with granite masonry; the granite for concrete and masonry facing will be obtained from the Government quarry at Moruya; the main arch trusses and girders of approach spans to be constructed of silicon steel, the deck and minor members of bridge to be constructed of carbon steel.

    The tender provides for using Australian materials as far as practicable, and all materials other than steel will be wholly Australian. The steel plates will be rolled at Dorman, Long & Co.'s Redcar Works, near Whitby, England—plates have not yet been produced in Australia, as the demand is not sufficient to warrant the outlay for steel furnaces and plate-rolling mills—whilst, of the balance of the steel, viz., the angles, channels, and other sections, as much as can be supplied to meet the requirements of the contract will be produced in Australia.

    The bridge will be fabricated in Australia on the foreshores of the harbour between Milson's Point and Lavender Bay, where, as provided in the contract, special bridge fabricating shops are being erected by the contracting firm.

    4. TRANSFER OF TRAFFIC FACILITIES PROM MILSON'S POINT.

    To enable the bridge to be fabricated and erected it was necessary to make available the land on the northern foreshores of the harbour between Jeffrey-street and the railway station erected midway between Milson's Point and Lavender Bay and involved: —

(a) The diversion of the railway passenger traffic from Milson's Point to the new station at Lavender Bay.
(b) (b) The diversion of the tramway passenger traffic from Milson's Point along Dind-street and Glen-street to the new station.
(c) The diversion of the motor-bus passenger traffic from Milson's Point to the new station.
(d) The diversion of the Milson's Point passenger ferry to the new station.
(e) The diversion of the vehicular ferry traffic from Milson's Point to new ferry docks at Jeffrey-street.

    To make adequate provision for the railway passenger traffic it was necessary to remodel and repair the railway station which had been erected some years previously. The overhead bridge and stairways to the platforms were demolished, and access given to the ferry by means of an end platform, thus obviating the use of stairways by the railway passengers, as had been necessary when the station was previously in operation.

    To give the tramway passengers direct access with the new ferry the tramway has been diverted along Dind-street to Glen-street, which street is parallel to the new railway station and ferry wharf, but is some 40 feet higher.

    To enable motor-bus and other vehicular traffic to serve the new station, it was necessary to widen Dind-street and Glen-street, also to provide a bus and cab stand adjacent to the station where passengers could load and unload without interfering with the traffic in Glen-street.

    To give the tramway and motor-bus passengers and other pedestrians ready access from Glen-street to the railway station and ferry, three escalators or moving staircases having a rise of 35 feet, have been provided; these escalators have a passenger capacity each of 10,000 per hour. For passengers who will not use the escalators, two stairways, 7 feet wide, have been provided, also an electric lift for elderly or maimed people.

    To make provision for the ready access of the railway, tramway and other passengers to and from the ferry steamers, barriers to separate the incoming from the outgoing traffic were erected on the wharf, the ramps were altered and a large reinforced concrete pontoon provided.

    In the five hours, Sunday night, 27th July, 1924, at 11-30 p.m., and Monday morning, 28th July, at 4-30 a.m., the necessary alterations were made to the railway and tramway tracks and to the railway station to enable the change-over to be made at 4-30 a.m. on 28th July, 1924, as arranged.

    The transfer of the ferry station from Milson's Point was carefully thought out and was carried out without any inconvenience to the travelling public; the facilities provided for dealing with the railway, tramway and other pedestrian traffic are working well and have given complete satisfaction.

    To enable the vehicular ferry traffic to be diverted to Jeffrey-street, new ferry docks in duplicate, capable of accommodating the largest vehicular ferry punts have been constructed. The flaps of the docks are operated both electrically and by hand. A new roadway has been constructed from the Jeffrey-street ferry docks parallel to Alfred-street as far as Broughton-street. By routing the traffic along Pitt, Fitzroy, Burton, Broughton and McDougal streets, the vehicular traffic can be kept clear of the approaches at all stages of construction. The vehicular ferry docks and the roads in approach as far as Pitt-street were completed on 30th June, 1925.

    5. CONSTRUCTION OF NORTHERN APPROACH

    The roadway and railway approaches included in the Act, but not included in the work for which tenders were called, are being constructed by day labour.

    To inspire confidence in prospective tenderers that a tender would be accepted, and to enable the railway goods traffic to be diverted from Milson's Point to a new station in North Sydney with as little delay as possible once a tender has been accepted, the Minister approved of the Chief Engineer's recommendation that the construction of the Northern Railway approach from Bay-road Station to North Sydney Station should be undertaken some six months before tenders closed for the main bridge. Accordingly, on Saturday, 28th July, 1923, the Honorable R. T. Ball, M.L.A., Minister for Public Works and Railways, performed the ceremony of turning the first sod of the Northern Railway approach before a large and distinguished audience, representative of the Parliament of New South Wales, the City of Sydney, and the shires and municipalities on the northern side of the harbour. The function was arranged by the councils of the shires and municipalities on the northern side of the harbour, the Mayor of North Sydney—the late Alderman G. T. Clarke—presiding.

    On the following Monday, 30th July, 1923, the Field Office was opened in Bolwarra Flats at the corner of Walker and Blue streets, and preliminary work was commenced next day.

    The properties required between Bay-road and Walker-street were resumed and demolished, a stone crusher, air compressors, and other plant were installed and electrically operated with current supplied by the Railway Department. On19t September, 1923, the current was first switched on, thereby operating the air compressors and the jack hammer installation.

    The first holes were drilled and the first blasts in connection with the rock excavation were fired at the site of the North Sydney Station on that day, thus inaugurating this great work. The officers of the Department present on that occasion were the Hon. K. T. Ball, M.L.A., Minister for Works and Railways, Mr. T. B. Cooper, Under Secretary, the Chief Engineer, Dr. J. J. C. Bradfield, Miss K. M. Butler, secretary to the Chief Engineer, and Mr. K. Fraser, Resident Engineer.

    A contract for the construction of two reinforced concrete bridges, viz., an arch bridge carrying the railway over Euroka-street, and a girder bridge carrying the roadway of Bank-street across the railway was let to the State Monier Pipe and Reinforced Concrete factory, the contract amounts being £8,792 and£4,018 respectively.

    On 9th January, 1924, the headings for the tunnel between Miller-street and Bank-street were commenced, and on 18th June of that year the headings met, the length of tunnel being 22 chains. The tunnel has since been completed and lined, the first train passing through the tunnel to the temporary goods yard at North Sydney on 26th March, 1925, the date of laying the foundation stone of the main bridge.

    Some of the sandstone excavated from the open cuttings and tunnels was crushed into sand and concrete metal and used for making the concrete in the retaining walls between Bay-road and Ancrum-street for lining the tunnel; some of the excavated material was spoiled either at the head of Berry's Bay on Crown land leased by the late J. Y. Mills, or at the head of Lavender Bay to increase the area of the park there, about 1½ acres of land being levelled up at Berry's Bay, and an additional ½ acre added to the park at Lavender Bay; the remainder of the material has been used either as filling in the railway approach or in lining at Glen-street and at the Jeffrey-street Ferry Docks, or has been placed temporarily at Brisbane-street to be used later as filling and concrete metal. Approximately 140,000 cubic yards of excavated material have been so disposed of.

    Up to 30th June. 1925, the progress made in the main items of construction is as follows: —

Excavation in open cutting … … … … 71,499 cubic yards.
Excavation in tunnelling … … … … 35,124 „ „
Concrete in retaining walls … … … … 4,848 „ „
Concrete in tunnel lining … … … … 6,234 „ „
Fencing Temporary and permanent … … … … 5,075 lineal feet.
Railway track ballasted … … … … 1,455 „ yards.

    The construction of the railway approach necessitated the deviation of Carr-street; the new road has been planted on the side adjacent to the railway with tallow-wood trees.

    6. LAND RESUMPTION.

    To enable the construction of the main northern approach to be undertaken certain properties between Bay-road Station and Bank-street and between Miller-street and Walker-street had to be resumed and demolished, whilst property fronting McDougal street has been resumed and demolished to form an area for storing spoil from the excavation.

    To enable Messrs. Dorman. Long & Co, to erect their workshops at Milson's Point and to accommodate the tram and motor-bus traffic in Glen-street, properties had to be resumed in Glen, Dind, Northcliffe, and Paul streets. To enable Dorman. Long & Co. to commence work on the northern side of the harbour and to divert the vehicular traffic from Milson's Point to Jeffrey-street certain properties fronting Campbell-street, Pitt-street. Fitzroy-street, and Broughton-street have been resumed and demolished. Vacant possession of this area was given to Dorman, Long- & Co. on June 30, 1925, up to this date the Contractors were unable to undertake any work in connection with their contract on the northern side of the harbour.

    Up to 30th June, 1925. 139 properties were sold for demolition, the amount received being £7,576 10s. 8d.; these properties were auctioned for demolition by Messrs. Craig and Herring and Mr. Val. C. Woodberry.

    The amount paid for land resumption up to 30th June, last was £119,948 8s. 7d.

    7. DORMAN, LONG & Co.'s CONTRACT — CHECKING PLANS IN LONDON.

    On 30th April, 1924, a staff consisting of Miss K. M. Butler, secretary, and Messrs. Stuckey, Holt, and Powys, technical officers. in accordance with the conditions of the specification and contract agreement were sent to London to cheek the plans, calculations. &c. On 30th July, 1924, the Chief Engineer left for London to finalise the work of the stall and to sign the plans. The staff left London in November, 1924, via Canada and the United States, reaching Sydney on 10th January, 1925.

    When in England a visit was paid to Dorman, Long & Co.'s Steel making plant, rolling mills and constructional works at Middlesbrough and at Redcar, near Whitby. The Sydney Harbour Bridge is unprecedented in size, and the rivetting will be the heaviest yet undertaken. Many of the rivets will be 1¼ inches in diameter, and over 9 inches long between the head and snap. At Middlesbrough many experiments were undertaken to ensure that the rivetting will be as perfect as possible. The best results were obtained with rivets having 1/32-inch taper in their length, the rivet holes being drilled 1/32 inch larger than the diameter of the rivet. Special pneumatic tools for closing the rivets were designed and experimented with to ensure perfect workmanship, and many experiments were also made in heating the rivets in electric furnaces, also in coke and oil furnaces.

    The first cast of silicon steel for the bridge was made and rolled into plates and billets, the latter being drawn into wire, which was spun into cables to be used in the erection of the bridge.

    Specimens cut from the plates in the direction of rolling and transverse to the direction of rolling were tested in tension and bending. All specimens fulfilled the terms of the specification. Rivet rods were flattened out under a steam hammer to show the ductility of the .steel. Tensile tests of the cables spun from the silicon steel wires were made at Lloyds Testing House-, Cardiff.

    After very careful study and after many consultations with Messrs. Dorman, Long & Co., Sir Douglas Fox and partners, their Consulting Engineers, and Sir John Burnet and partners, their Consulting Architects, the principal type plans were approved by the Chief Engineer and signed by him in London.

    8. DORMAN, LONG & Co.'s CONTRACT — FREIGHT STEAMERS.

    An order was placed on 3rd July, 1924, by Messrs. Dorman, Long & Co., with the Government Dockyard, Walsh Island, Newcastle, for the construction of three vessels having a carrying capacity of 400-tons. These vessels are required for freighting granite, aggregate, &c., from Moruya to Sydney.

    Up to 30th June, 1925, one vessel only has been delivered, the s.s. " Dorlonco." This vessel was delivered on 3rd April, 1925.

Gross Tonnage … … … … 420.11 tons.
Registered Tonnage … … 161.09 ,,
Engines … … … … … … … … 86 N.H.P.
Indicated Horse-power. 630
Length … … … … … … … … 147 feet.
Beam … … … … … … … … 26.6 feet.
Bunker capacity … … … … 45 tons.
Steaming … … … … … … … 10 knots.

    9. DORMAN, LONG & Co.'s CONTRACT — THE MORUYA QUARRY.

    From the quarry at Moruya the granite facing for the piers and abutment towers and the granite aggregate for the concrete will be obtained. Developmental work at the quarry commenced on 1st December, 1924.

    The quarry consists of the following main items of plant: —

Wharf.— Dimensions approximately 60 ft. x 40 ft. Designed to carry two 15-ton steam loco, cranes for loading dressed granite.

Power House and Dressing Sheds. — These buildings are in three bays of 32 feet and cover an area of 150 ft. x 96 ft. The construction is steel framing with corrugated iron roofs and sides.

    Two of the above three bays are utilised for the stone dressing sheds, and are each equipped with a 5-ton electric over-head travelling crane. The work of dressing the stones will be carried on in these sheds, which are fitted up with the necessary air and water pipe lines—the tools being mainly pneumatic.

    The power house contains a power plant comprising two 205-kW generating sets, driven by 300 b.h.p. internal combustion engine — complete with starting engines. Two 380 cubic feet per minute 12in. x 12 in. air compressors are installed in the power house, each driven by a 65 h.p. motor. These compressors supply air for the whole of the pneumatic tools, including rock drills, surfacing machines, hand dressing tools, &c.

    The power house contains a centrifugal pump driven by 11 h.p. motor for returning the cooling water for main engines and compressors back to the storage tanks. The power house bay is equipped with a 7-ton overhead hand crane for use in lifting engine parts.

    Part of the power house bay will be used for a repair shop, and contains a motor-driven circular saw, lathe, &c., together with the necessary line shafting and small machine tools.

    The construction of the power house and dressing sheds involved the levelling of the site and the excavation and concrete work for the foundations of the building and the heavy engine beds.

    Crushing and Screening Plant. — This plant has been erected on a site near the river, to the west of the main buildings. The plant is designed for the crushing of granite for aggregate, and comprises two crushers, a bucket elevator, a revolving screen, together with large steel storage bins capable of storing between 700 and 800 tons of crushed stone. The bins deliver their contents on to a belt conveyor — loading into the boats by gravity. The whole of the plant is driven by electric power. The work of erecting this plant involved the excavation and concrete work for the foundations, and also the construction of a timber dolphin or stay, to support the discharge end of the conveyor and to allow vessels to tie up when being loaded.

    Water Supply for Power House, &c.—The water supply comprises an oil-driven pump at the supply end — approximately 1 mile from the quarry - delivering through a pipe line to seven elevated 4,000 gallon tanks. The water passes through a steel filter tank before being stored. From the storage tanks the necessary pipe lines to power house and shops and return lines from the power house have been installed. There are also three 2,000 gallon rain water storage tanks adjacent to the dressing sheds.

    Stone Dressing Machines and Tools. — Ten pneumatic Henderson surfacing machines for part of the heavy tool equipment. These are to be grouped outside the dressing sheds, and will be served by a 5-ton electric scotch derrick crane.

    Cranes. — The following cranes are now on the site: —

        One 7-ton hand overhead travelling crane in power house.
        Two 5-ton electric overhead travelling cranes in dressing shops.
        One 15-ton steam loco. crane.
        One 7-ton steam scotch derrick crane.
        One 5-ton electric scotch derrick crane.
        One 5-ton loco, steam crane.
        One 1½-ton hand derrick crane.

    Railway Tracks and Rolling Stock. — The site is served by the necessary 4 ft. 8½ in. gauge tracks for the loco, cranes and tip waggons, and also by narrow gauge tracks for two petrol locos for the haulage of tip waggons and stone bogies for the conveyance of stone and spoil and for feeding the crusher plant.

    In addition to the main items of plant mentioned above, the list of quarry plant includes all the necessary small engineers' tools, chains, slings, small pneumatic tools for stone dressing, &c.

    The plant and equipment is now practically complete.

    10. DORMAN, LONG & Co.'s CONTRACT — CONSTRUCTION WORK AT DAWES POINT.

    The area at Dawes Point was handed over to the contractors on November 1st, 1924, when steps were taken to enclose the area and erect the plant. Excavation for the main southern pier was commenced on 19th January, 1925.

    On 26th March, 1925, the foundation stone of the southern abutment tower was laid by the Hon. R. T. Call, M.L.A., Minister for Public Works and Railways, in the presence of His Excellency, Sir Dudley de Chair, M.V.O., the Hon. Sir George W. Fuller, Premier, Sir Arthur Dorman, Bart., and Sir Hugh Bell, Bart., Directors of the firm of Dorman, Long & Co., who journeyed from England to be present at the ceremony.

    Wharf. — A timber wharf for loading and unloading materials has been erected in front of the south main abutment; this wharf was built by the Sydney Harbour Trust. The size of the wharf is 110 ft. x 21 ft.—the deck level being 8 feet above standard datum.

    Haulage Incline. —This incline was built from the water-front at the south abutment tower extending to the end of contract at the south terminal abutment. Much of this incline is built on earthwork, but the southern end was built on a line of timber trestles approximately 500 feet long, carrying a single 4 feet 8½ in. track. The incline is operated by an electric haulage winch at the south terminal abutment, mounted on a heavily braced timber frame.

    The southern end of this incline passes over George-street North and York-street North, leaving openings for tram and other vehicular traffic. The incline was completed on 15th June, 1925.

    Main Staging. — The falsework for approach span No. 1 on the west side was completed on 7th June, and on the east side on 14th July. The erection of both sets of falsework necessitated a considerable amount of excavation and concrete work for foundations and on account of passing over two public thoroughfares and a double set of tram-lines, the erection of this span of falsework was necessarily somewhat slow and tedious. The erection of this falsework also involved the assembly and erection of two heavy 5-ton steam loco, cranes at a high level.

The following plant is now in operation at Dawes Point: —

    Cranes—
        One 7-ton steam derrick crane 110 feet jib.
        Two 7-ton steam derrick cranes 65 feet jib.
        Three 5-ton steam loco, cranes.
        One 7-ton steam loco, crane.
        One 25-ton electric derrick crane.
        One 3-ton hand crane.

    Air Compressors—
        Two portable air compressors, complete with air receivers, mounted on trucks with wheels and axles,          each compressor capable of taking six squads of rivetters.

    Centrifugal pumps—
        Two 6-inch medium lift centrifugal pumps with 46 h.p. motors.

    Lorries-
        Three 5-ton Motor lorries.
        One 5-ton motor lorry complete with timber trailer.

    Motor Launch.
        One 10 h.p. Motor Launch for staff use between north and south sides.
    Concrete Mixers—
        Two 1-cubic yard capacity concrete mixers.

    Transformer House. —A transformer house has been erected containing a balancer for converting 600 volt current to 275 volt direct current, and a transformer transforming 6,600 volts alternating current to 1,440 alternating current.

    The above comprise the main items of plant now on the site at Dawes' Point.

    During the year ended 30th June, 1925, the work paid for is as follows: —

        Earth excavation … … … … … … … 6,350 cubic yards.
        Rock excavation … … … … … … … 5,104 „
        Concrete No. 2 … … … … … … … 971 „ „

    11. DORMAN, LONG & Co.'s CONTRACT - CONSTRUCTION WORK AT MILSON'S POINT.

    The area at Milson's Point on which the workshops will be built was handed over to the contractors on 1st November, 1924, and the whole of the area required for the purposes of this contract other than three properties, viz., the Milson's Point Hotel, Langdon and Langdon's timber yard and the Sydney Ferries property, was made available to the contractors on 3oth June, 1925.

    Wharves. — Two wharves have been constructed. The main wharf, adjacent to the new workshops, was constructed by the Sydney Harbour Trust, commenced on 30th January, and finished at the end of April. This wharf is 250 feet long x 50 feet wide, and is designed to carry two 10-ton travelling wharf cranes of the portal type, for unloading purposes. To admit of large ocean-going steamers lying alongside,. the draught of water at the wharf is 28 feet; a considerable amount of dredging had to be carried out to obtain this draught. Two large dolphins have been constructed 62 ft. 6 in. from each end of the wharf in order to moor large vessels safely.

    A small wharf is being constructed in front of the north main abutment for unloading materials for the northern approach spans. This wharf is similar to the small wharf at Dawes' Point, and will be 100 feet long x 21 feet wide, deck about 12 inches above Standard Datum. It was commenced by the Sydney Harbour Trust on 22nd June.

    Workshops. —To form the site for the workshops, approximately 46,000 cubic yards of rock and earth will have to be excavated—to the end of June the steelwork erected comprised the end transverse stock bay—180 feet x 70 feet, and one bay of the main shop measuring 130 feet x 50 feet. The approximate tonnage of steelwork erected being 190 tons.

    Plant. — The following list of the main items of plant now on the Milson’s Point site: —

       Two ¾-cubic yard concrete mixers.
        One portable sit compressor (same specifications as those at Dawe’s Point.
        One 7-ton locomotive crane.
        One 7-ton steam derrick crane – 65 feet jib.
        One 7-ton derrick crane – 110 feet jib.
        A transformer house the same as the transformer house at Dawe’s Point.
        Two 1 cubic yard concrete mixers (15 h.p. motors).
        One 3-ton hand crane
        One stone crusher.

        Besides the above there are grabs, skips, forges, anvils &c.

    12. LAND TAX.

    To defray one-third the capital cost of the bridge and land resumption, a land tax of one halfpenny in the pound has been imposed on the unimproved capital value; of land situated within the city of Sydney, the, municipalities of North Sydney, Mosman. Manly, Lane Cove and Willoughby, the shires of' Kuring-gai and Warringah, and portion of the shire of Hornsby.

    The tax was imposed first in the year 1923, and Table 1 gives, for the years 1923, 1924, and 1925, the unimproved capital value of the land in the shires and municipalities, the number of assessments, and the amount of tax.

    The total amount to be derived from the tax for the three years ending December, 1925, is £391,949 14s. 9d., of this amount £327.539,7s. 4d. was paid to the special fund up to 30th June, 1925. leaving a balance of £64,410 7s. 5d. to be paid before December next.

    When the Legislative Council, in 1922, was considering the financial clauses incorporated in the Enabling Act, the Chief Engineer submitted a report in which he forecasted that the unimproved capital value of land in the city of Sydney would continue to increase at the rate of 4 per cent, per annum, and in the shires and municipalities on the northern side of the harbour at the rate of 8 per cent, per annum. On this basis he estimated that the tax which would be derived for the years 1923, 1924, and 1925 would amount to £382,779. From Table 1 it will be seen that the actual amount will be £391,949 or 2.4 per cent, greater than his estimated amount.

    13. AVENUES IN APPROACH TO BRIDGE.

    In November, 1923, the conference summoned by the then Lord Mayor to advise which streets in the city should be widened to adequately provide for the traffic to and from the Sydney Harbour Bridge, concurred in the proposals submitted by the Chief Engineer for a crescent connecting York, Clarence, and Kent streets with the main avenue to the bridge, extending Watson-road to the Main Bridge Avenue; the widening of Kent-street from Gas-lane and extending Kent-street as widened to George-street, also the widening of York-street from the crescent as far as Wynyard-street.

    In April, 1925, a scheme prepared by the Chief Engineer for widening York-street and Kent-street from 60 feet to 81 feet wide, for connecting these streets and Clarence-street with the main bridge avenue by means of a crescent, for extending Kent-street to Goulburn-street and York-street to Wynyard-street, and for making a new east-west avenue from Taylor-square via Goulburn-street and MacArthur-street to George Street West near the University was submitted to the City Council for its consideration. Up to 30th June, 1925, the City Council had not reported on the proposals placed before it by the Minister.

    Under the Bridge Act, the Minister, the Hon. H. T. Ball, in April last approved of the widening of York-street from Grosvenor-street to Wynyard-street, likewise the widening of Kent-street from Gas-lane to Napoleon-street, and the construction of a crescent connecting York, Clarence, and Kent streets with the main avenue to the Bridge, also the provision of two parklets fronting the crescent between York and Clarence streets and between Clarence and Kent streets.

    14 TRIANGULATION SURVEY.

    The most important measurement in the construction of the bridge will be the location of the four main arch bearings, two on either side of the harbour. The distance across the harbour from centre to centre of pins of each pair of bearings is to be 1,650 feet, whilst the two arch ribs are to be 98 ft. 6 in. apart centres and parallel to each other. To locate these four points it is necessary to determine with the greatest accuracy the distance between two fixed points on the centre line of the bridge, one on either side of the harbour. The two points to be fixed are the centres of two brass plugs embedded in concrete blocks, and each protected by a cast iron box.

    As it is not possible to measure the distance across the harbour between these two fixed points, two base lines were established, partly in the Botanic Gardens and partly in Government House grounds, the length of which could be measured correctly, and the measurement corrected for temperature. The length of ground chosen for each base line is suitable for correct measurement consisting as it does of lengths of level path and mowed lawn surfaces away from any heavy traffic of a disturbing nature. These base lines were carefully measured with two 100 feet Invar steel tapes imported from England and tested at the National Physical Laboratory at Teddington, London. and were compared with the standard at the Lands Department. Sydney, and found to agree. The base lines were also checked by the Lands Department.

    A series of triangles was arranged to connect each base line with the centre line, the length of which had to be determined. The angles of the series of triangles were read by a 8-inch Watts theodolite specially made in England for this survey; by this theodolite angles can be read correctly to one second.

    Having determined one side of a triangle and measured its three angles, the other sides were calculated, and so on throughout the series of triangles until the length of the line to be determined was arrived at.

    The survey was made by Surveyor Amphlett, B.E. The distance between the two fixed points on the centre line was found to be 2268.447 feet, Mr. Amphlett's calculations using either base line giving this figure.

    For the purposes of construction this distance will be taken as 2,268 ft. 5⅜ in. Knowing the accurate distance between the two fixed points, the length of span, viz., 1.650 feet. can be fixed from these two points on the centre line and the position of each pair of bearings on either side of the harbour determined. The centres of each pair of bearings on each side of the harbour will be 98 feet 6 inches apart at a temperature of 60 degrees Fahrenheit.

    16. FINANCIAL.

    The total expenditure including expenditure prior to 30th June, 1923, is as under: —

                J. J. C BRADFIELD
                    Chief Engineer, Sydney Harbour Bridge.
                        1st September 1925

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