KAWARAU SUSPENSION BRIDGE.

Cromwell Argus, Volume IV, Issue 190, 1 July 1873, Page 5

KAWARAU SUSPENSION BRIDGE.

The completion of the first bridge erected on the Kawarau River was celebrated yesterday afternoon, when a large concourse of people assembled to witness the ceremony of christening the bridge and declaring it open for public traffic. The site of the structure is about three miles south of Cromwell, on the line of road leading to Bannockburn, Garrick Range, and the Nevis. Self-acting punts, propelled by the river-current, have hitherto supplied the means of crossing ; but the great increase of traffic on the road, the impediments caused by the necessarily steep gradients of the ferry approaches, the delays and interruptions frequently caused by the rising and falling of the river, and the desirability of providing more safe, speedy, and reliable means of transit fur all kinds of traffic ; —all these considerations pointed to the conclusion that a bridge had become an almost imperative necessity. To the enterprise and energy of Mr John M'Cormick, one of our oldest residents, is primarily due the initiation of the Kawarau Bridge ; and it is a curious coincidence that Mr M'Cormick was also the first to establish a ferry-boat on the Kawarau at the time of the great rush to Fox’s, or as it is now called, the Arrow River. The bridge now under notice was projected by Mr M‘Cormick some sixteen months ago ; and about three months from that time "the work was commenced by Messrs M'Cormick, Grant, and Richards, who made an arrangement with the Provincial Government to construct the bridge at their own expense on condition that the approaches should be provided tor out of the public revenue. Before entering upon a detailed description of the bridge, it may not be out of place to say a few words regarding the general principle of suspension-bridges, and to indicate the circumstances in which they are usually found most suitable and convenient. The proper and legitimate use of suspension bridges is to carry ordinary roads over large spans, where the rolling loads are not great in proportion to the weight of the bridge itself, and not very rapid in their motion. In the bridges the roadway is suspended from wires or chains passing over piers and towers, and firmly fixed in the ground behind them. When the roadway is equally loaded over its length, the curve of the wires or chains is a parabola. The principle is by no means new, suspension bridges having been in use in China for hundreds of years. Many beautiful examples are to be seen in various parts of Europe and America ; and among others, the Menai Bridge, in Wales, 580 ft. span ; the Clifton Bridge, near Bristol, 703 ft. span ; and the Niagara Bridge, which connects tire railways of Canada and New York. Niagara Bridge is of a single span of 822 ft., and carries three lines of rails, over which trains pass at the rate of ten miles an hour. The platform, which is 250 ft. above the river, is supported by four wire cables, each containing 3(540 wires. The longest bridge in the world is the Victoria (tubular), over the St. Lawrence; its length is about sixty yards less than two miles, and the cost of construction was £1,700,000. The Kawarau Bridge, as indicated above, is constructed on the suspension principle, and wire cables are used instead of chains, — the former being more generally used in the Colonies than elsewhere. The bridge is suspended on twenty-eight wire cables—fourteen on either side, —each cable being composed of six smaller ones, with seven wires in each. The cables average 41 inches circumference. The dimensions of the bridge are as follow : —span, from pier to pier, 148 ft.; breadth between the wires, ISfr. Gin.; clear width of roadway between rail and rail, 12ft. The beams are suspended on 58 vertical rods,

'illy an inch in diameter ; the rods hearing above and below on substantial 4i inch dips" The lower end of each rod is fitted with a 12-inch screw, to enable the adjustment of the bridge to bo altered if found necessary. The beams, 20 in number, are each llin.'x Bm., are braced crosswise with 4in. x 4in. timber, and stayed longitudinally with timber of the same dimensions. The roadway is formed of two layers of diagonal planking, the first layer being 2|in, thick, and the second 2in. The protecting rails are 6ft. high, made of 7in. x bin, stuff, with diagonals bin. square. The wood used in the kerbing on either side of the roadway is Sin. x bin. f J> camber of the roadway elevatesthe centre of the bridge two feet above the level at either end ; and the height of the platform above the average height of the river is about 60ft. At the centre of the bridge, the cables have a deflection of lift, bin. below the level of the pier-heads. The dimensions of the main pier may be roughly stated at 28ft. x 10ft. at the base, decreasing to 20 x 8 at top ; height at level of roadway bOft.; with hollow chambers behind. At the back of the chambers, the pier is built in steps on the solid reef. The object of the chambers is to prevent any slip or pressure from the hill from affecting the main pier. The pier on the north side is of the same width and thickness as the main pier, hut is only 12ft. high, being built upon a natural rock abutting on the river hank. The small piers are four in number ; the base sections being 7ft. x sft., and top sections sft. x 4ft. These piers are 13ft. in height, built of cut and dressed masonry (technically known as rustic ashlar), in courses of 12in. each. On the small piers rest the saddles, which receive and carry the wire cables. The saddles are secured to the piers by means of Lewis bolts, and the ironwork connected with each saddle weighs over two tons. The anchoringplates are fixed from 65 to 70ft. behind the piers, in tunnels driven through solid rock where such existed. Where the reef was not solid, masonry of a substantial character was substituted. The angle of the wire from the saddles corresponds with the angle made by the weight of the bridge. In order to admit of inspection at any time, manholes are left immediately over the anchorings. The an-choring-plates, with the sheaves, weigh about three tons. The total weight of the ironwork in the bridge is 16 tons. Each of the 28 wire cables used in the construction of the bridge is capable of sustaining a weight of 50 tons ; so that the carrying capacity of the whole is equal to 1400 tons. It was estimated that during the christening ceremony yesterday the aggregate weight of humanity on the bridge was between 40 and 45 tons ; yet, so effectively had the work of “stiffening” been performed that there was no greater vibration perceptible than would be caused by a horse walking across from end to end. The approach on the north side lias a maximum gradient of 1 in 9 ; is 20ft. wide, and 12 chains in length. About 46,000 cubic yards of gravel and stone—chiefly large boulders—were excavated in the formation of this approach. The gravel was sluiced into the river by aid of powerful streams of water obtained from one of the Gorge races ; but a vast amount of time and labour was consumed in blasting and removing the boulders before mentioned, _ On the south side, the approach is 30 chains in length, extending to the top of the rise at Richards s hotel, and is cut through rock and clay the whole distance. This of road would be much improved by gravelling, as has been done on the opposite side. The cost of the bridge is said to be from 16000 to £7OOO ; and the contracts for the approaches (which were constructed at Government expense) amounted to something near £2500. The rates of toll have not been definitely fixed, but they will probably be the same as those lately charged for crossing the Kawarau ferries. Let ns hope that only a short time will elapse ere the bridge is transferred to the Government and made free to all comers. THE OPENING. Probably not fewer than 350 people assembled on the bridge to witness the ceremony of christening, and to share in the rejoicings at the successful termination of the bridge Company’s labours. Hie Cromwell Brass Band commenced the proceedings by playing the “ Palermo Quickstep” as they marched towards the bridge, and led half-way across it. Here they halted, and Mrs M ‘Cormiek, the lady upon whom the task of christening devolved, was led forward to the post of honour by the Mayor of Cromwell; and the pendant bottle of sparkling champagne having been placed within her reach, she addiessed a few appropriate words to the spectators, and then, gracefully dashing the bottle against the railing, it broke into a thousand fragments, and the spray of its contents bedewed the faces of the bystanders. The lady then finished her part by wishing “Success to the Kawarau Bridge.” Hie Mayor then read the following certificate from Mr 11. Hay, Chief Draftsman to the Provincial Engineer’s department, who had coma from Dunedin expressly to pass the work “ io Messrs Grant, Richards, and Co., “ Kawarau Bridge. “Sirs, —According to instructions received from the Provincial Engineer. I hereby declare the bridge erected by you to he in a fit and proper condition for the accommodation of public traffic, “ R. Hay, “Pro D. L, .Giupson, C.E., “ Provincial Limuicer. “30th June 1873.” His Worship afterwards declared the bridge ‘buy opened lor trailic, amt a- the close of an eloquent and appropriate speech (which was

loudly applauded) invited the public, as the guests of the Ib id ,e Company, to adjourn to the south end of the bridge for refreshments. Spread in lavish profusion upon tables placed there for the purpose, were sandwiches, fruits, and confectionery of the choicest kinds ; whilst the liquor department was furnishel on a scale of equal liberality and abundance. The air being very cold, a large fire was made close by, which added greatly to the comfort of the merry-makers. The following toasts were proposed and responded tot—- “ Her Majesty the Queen,” by the Mayor. “The Bridge Company,” by the Mayor: responded to by Messrs Grant and Richards. “The Mayor and Council of Cromwell,” by Mr Richards : responded to by the Mayor. “ The Superintendent and Provincial Council,” by the Mayor. “ Prosperity to the Bannockburn and Garrick districts,” by Mr I. Wright: responded to by Mr Crombie. “ Success to our Quartz Reefs and Reefers,” by Mr Marsh : responded to by Mr Stephenson. “The Commercial, Agricultural, and Banking Interests,” by Mr Grant : responded to by Mr ■Jolly, Mr Slianly, and Mr M‘Owen respectively. “ Garrick Range Water Race Company,” and Hie “ Cromwell Brass Band,” by Mr Richards : responded to by Mr Taylor and Mr Whetter. “The Ladies,” by Mr Grant: responded to by Mr Talboys. “ The Press,” by Mr Colclough : responded to by Mr Matthews. The proceedings were brought to a close by the Band playing the National Anthem ; and at half-past four a general start was made for home.