THE WINGATUI VIADUCT.

Otago Witness, Issue 1825, 12 November 1886, Page 16

THE WINGATUI VIADUCT.

At the invitation of Messrs R. S. Sparrow and Co., the contractors for the construction of the iron bridge over Mullocky Gully, upwards of 100 ladies and gentlemen had a trip over the first section of the Otago Central railway on Tuesday. The party comprised a very large number of ladies, and ainougst the gentlemen we noticed Messrs A.Burt, Henderson, Morrison, W. Swarm, J. M'Donald, Shacklock, M. Sinclair, Graham (engineer of gasworks), W. P. Watson, and W. Watson. The special carriages provided in conuectiou with this trip were attached to the southern train which left the railway station at 9.20 a.m., but at Wingatui Junction the guests had to leave the carriages and thence were taken to the site of the viaduct, a distauce of about 10 miles, in ballast waggons, in which seats had been placed. The run across the plain and to Mullocky Gully in the trucks was however a pleasant one, as the weather was fine and the waggons ran smoothly. After leaving the plain the country could not have been rougher or more barren, and there could be no doubt that it is only fit for grazing purposes, if it is even of much value as pastoral country. It should, however, be remembered that this has always been represented as one of the worst portions of the country on the route of the Otago Central, and that from this is opened a large extent of rich arable land iniheStrathTaieri. The party arrived at the end of the Wiugatui section at half-past 11 o'clock, and found that ample provision had been made for their entertainment. Two tents had been erected, one of which, a large marquee, was fitted with tables and benches, and contained a plentiful supply of refreshments. On arriving at the end of the journey one of the first things done was to inspect the bridge. THE VIADUCT. This work, we understand, is unique in railwaybridge architecture. It was designed by Mr W. N. Biair, and is remarkable as being by far the largest wrought iron structure in the Australasian colonies. The first impression created js one of astonishment at the magnitude of the work, its immense height and its slender proportions. When finished the sensation which passengers must experience when passing over it, if they look down, will be more exciting than agreeable, for the trains will shoot across the gully ab a height of 150 ft above the level of the creek. In comparison with this the mildly exciting trip round the Blueskin cliffs would be a very tame affair. The most remarkable characteristics of the viaduct are its great height aud its lightness, and viewed from the creek its mass've iron girders seem flimsy, and it looks far too delicate to bear a train across in safety. This appearance is doubtless misleading, for the calculations have been made upon approved basis far too reliable to permit of any risk in this particular, and a close examination of the piers, spans, and girders shows that the work is more massive than one would suppose when lookiug at the structuro as a whole. As is generally known, the construction of this viaduct has greatly retarded the progress of the line, and it is therefore satisfactory to learn that this work will now be completed in about four months from the present time. The formation of the line is finished as far as Mount Allan, and when the vi{iduct is fiuished the permanent way can be laid over another section and we should be within measurable distance of seeing a useful section of the Otago Central railway open for traffic. The viaduct consists of eight lattice girder spans, sustained by two stone buttresses and seven piers, two of concrete and five of iron — what are known as 16in box or square piers. The length between the outside of the abutments is 690 ft lOin, the width between the eeutres of the handrails 12ft Bin, and the height from the creek to the top of the parapet 153 ft, or from the foundations 154 ft Bin. The first two spans from the town end are 66 ft each ; next there are three great spans of 106 ft, and the remaining three are the same as the first two, 66ft spans. ' The first pier on each side of the viaduct is of concrete, and the remaining five are of wrpught iron — one of 41ft, two of 49ft each, and the two centre piers each 109 ft 6in in height. Messrs Black and Allison, of Dunedin, were the successful tenderers for the masonry and concrete work, and haye completed their contract satisfactorily, the work having been passed by the department. This work comprises the foundations, two piers (the concrete ones), and the abutments, which are of schist. Some 'idea hi the extent of this work may be gathered from the fact that it consists of 6240 tons of snasonry.and concrete. By far the larger part ai the work is of course the ironwork, aud with this good progress is now being made, the coniractors, Messrs R. S. gparrow and Co., having imported a large amount of machinery to enable them to carry out their contract. The iron for the biidge was brought to the colony in the 6hape it leaves the rolling mills, and has been «ut, shappd, . and; parts riveted together at the works in Dunedin. EJyery bolt and rivet in the bridge has been made in tjje colony, Mr Sparrow havin&jmported special machinery for that purpose, as well as a hydraulic riveting machine similar to the one used ou the Forth bridge, at Home, and a right and left hand shearing machine, combined with a beambender. Some time was necessary to get this plant and the material required, but the delay in connection with the work has been caused chiefly by the severe frosty weather making it impracticable for the concrete work to be done expeditiously. A good deal of the bridge work has been ready in town for some time, but the erection of the bridge was not begun until about the middle of last September. Satisfactory progress is now being njaue. The first two spans have been erected, aud one of the largest spans (106 ft) is now nearly finished. It has been put together on the level of the lower concrete pier basis. Two of the wrought iron piers are also being erected, and as the piers rise the girder will be elevated by means of hydraulic appliances designed and manufactured by the contractors specially for this purpose. The girder will weigh about 40 tons, but it wili bfl lifted over 100 ft above the place in which it now re«ts, without any manual exertion and gradually that its motion will be imperceptible. As the girder ascends the bracings of the piers wSH be riveted, and when it reaches the same line as the concrete base of No. 3 pier a tramway will be laid across the girders, and tbe material for the piers and spans on the further side of the gully will be led across. After this the piers from the bottom of the gully will be finished, the ■epans being lifted to the same hfiigbt; as the 66ft *pans— the permanent level of the bridge. The three longspaus are the ouly ones that will be lifted by hydraulic power, the others being built oon staging. At the present time 14 men and •seven boys are employed on this contract at Mullocky Gully, but most of the work is done in the city, a^d shortly it will be practicable and •profitable to increase the number of bands engaged in erecting the viaduct. It may alsp be worth mentioning that the bridge is to re* eeive three ooats of the Jramntit© jmia* mauu«

factured at Nelson, that paint having been decided upon as most suitable for the purpose. The work is being done under the direction of Messrs Sparrow and Co.'s inansger (Mr Roberts) aud of their working foreman (Mr Henderson), aud in its progress it is supervised by Mr G. L. Cook (resident engineer) and Mr William Barclay (Government inspector for this work)

After the party had seen th« partly constructed viaduct, and had expressed muuh wonder at the magnitude of tho undertaking, au adjournment was made to tbe luncheon tent, and later in the afternoon several toasts were proposed. Mr A. Burt proposed the health of Mr Sparrow, and in doing so thanked him on behalf of the guests for his invitation aud his liberal hospitality. The work they had seen, he remarked, was an undertaking which a few years back it was thought could not be accomplished in the colony. Thanks to tho present Government, tenders had been called for the work within the colony, and fortunately our fellow townsman had succeeded in obtaining the contract. All the labour in connection with tho construction of this viaduct was being done in the colony, though the contrary had been stated. Had ib not been for this work a numof artizans would have had to leave the colony instead of finding remunerative employment in it. He proposed the health of Mr and Mrs Sparrow. Mr Sparrow returned thanks for the compliment paid him. He remarked that on several occasions the ironworkers had tried to induce previous Governments to get ironwork done here, but somehow they never succeeded in getting anythiug but promises, of which not one had been fulfilled. The present Government, however, lost no time in calling for tenders and getting several bridges in hand, of which this was the largest and most expensive. A large immber of men had been employed on this work for the last two years, who otherwise would have had to go to Victoria or to have swollen the ranks of the unemployed. He hoped the time was not far distant when he should invite his guests to be present at the completion of the work.

Mr M'Donald proposed the health of the designer of the bridge, Mr W. N. Blair; Mr WiLLtABi Watson proposed the health of Mr Barclay, the Government inspector, and Mr Cook, the Government engineer; and the health of "The ladies," and" A prosperous termination of the contract " were duly proposed and received with cheers.

The party left on the return trip at half-past 4, and arrived in Dunedin at half-past 6, having had a pleasant visit to the country and the privilege of seeing in progress one of the largest and most difficult pieces of engineering work ever undertaken in the colony.