THE WORKS AT THE HEADS.

Otago Daily Times, Issue 7336, 20 August 1885, Page 3

THE WORKS AT THE HEADS.

The costly and extensive works which the Harbour Board have undertaken at the Heads has now progressed so far as to make a visit of inspection particularly interesting. Yesterday Mr G. M. Barf,"the engineer, was joined in his periodical visit to the works by a small party, which included Messrs E. Wilson, J. T. Mackerras, J. L. Gillies, Phillips (gaoler), J. Baxter, Simpson, and a representative of this paper. The weather was exceptionally fine, and with the tide favourable, the Reynolds made a quick trip down, reaching the Heads at about midday. To those who have not visited the spot since the works were commenced the change is very striking. The large desolate flat known as the Northern Spit is beginning to look actually populous. The prison hulk is moored near to the shore for the accommodation of the | 40 odd convicts whose labour is employed,; and dotted about the flat are a number of neat1 comfortable houses, looking rather as if they were intended to form the nucleus of a favourite watering place. , The best of these residences are those erected for the inspector of works (Mr Stephens) and the chief warder, who has charge of the prison contingent. There are also | one or two stores and boarding-houses combined,' which provide food and sleeping accommodation but —by special arrangement—no liquor, and there are a handful of smaller buildings, mostly erected and occupied by those who are in some way connected with the harbour work, to say nothing of a collection of tents and huts nestling in a hollow near the beach.

The immediate cause of all this activity is seen in the shape of a pier-like structure jutting out seawards-with a slight inclination in the direction of Taiaroa Head opposite. This is the commencement of the enormous mole which the Harbour Board have undertaken to carry 4000 ft out into the sea with'the view of thereby confining the wandering waves within more correct and. proper limits, scouring away that bar which has so vexed the soul of the public generally, and making Otago Harbour the best and safest in New Zealand. To be strictly accurate, this massive timber structure is not the commencement of the mole. It is merely the means by which the thousands of tons of rock, which will compose the said mole, are to be pcecipitated into the deep, there to settle into a massive impenetrable wall that will defy the action of wind and tide for all time. Another possible means would have been to employ barges to deposit the material, but for many reasons the wooden staging is preferable. From the character of the staging alone a very good idea of the magnitude of the work it obtained. The structure is some 40ft in width, supported on piles of ironbark driven firmly into the sand, a span of 22ft being allowed between each. Sir John Ooode's original plan provided for 25ft spans, but as Mr Barr, by adopting the lesser space has avoided the necessity of underbracing, the alteration results in a considerable saving. The crossbeams and longitudinal sleepers which form the superstructure of this staging are very massive, as they need to be for the weight they have to bear. They carry-three-lines of rails, along-which trucks pass laden perhaps with some 50 tons of stone, which is tilted over en masse into the water below. As the visiting party yesterday reached the extremity of the 1000 feet of staging so far constructed, they had an opportunity of seeing one of these little consignments discharged. A locomotive driving before it nine or ten trucks came travelling up, and one after the other the well-balanced -receptacles were tilted •up, and the contents sent thundering down with a vibration that shook even that substantial structure. ;The 10 trucks were each loaded with about four tons of stone! In seven minutes this mass of 40 tons was snugly deposited beneath, and engine and trucks were -away to the quarries for a fresh load. This rock, which is being used for the formation: of the mole, is purposely quarried in blocks of varying size. There is a | quantity of quite small stone, mingled with I blocks weighing up to seven tons—the maximum lifting power of the crane employed at the quarry. The smaller material is specially useful in the way of filling in and binding the wall, while the heavier blocks of course give it weight I and solidity. The quantity of stone that | will have been deposited by the time this gigantic work is completed is almost incalculable. The mole is to be constructed to a level just above high water mark from end to end, and of course as its height .increases the width of its; base will spread proportionately At present, with the staging 1000 ft out, the depth is about 14ft at low water. The mole will have grown to some 30ft in height by the time it has reached its limit of 4000 ft, and its base will then probably be some 150 ft across—a truly enormous mass of stonework. The work so far as it has at present been pushed has not r.eaphed the extremity of the beach current, and until it has reaohed the regular tidal current no difference can be expected upon the bar As soon as this point is reached, however, a gradual improvement should become noticeable. Before leaving the staging, it may be mentioned that although iron bark imported from New South Wales has io be used for the piles, the superstructure is entirely of Native timber. Black pine was used for the first 500 feet, but Mr Barr then concluded that the red pine, a much cheaper timber, would be sufficiently durable for the purpose, and this has since been employed. The engineer estimates that it will last for some eight or ten years in its present position, far longer than is required for the completion of the mole, which it is hoped to finish within about 2§ years. The Harbour Board, by the way, contract for the material and construction of the staging, and the work which they retain in their own hands is therefore merely the quarrying and depositing of the stone. Leaving the staging and following the line of rails leading to the quarries at the northern head, a fufler idea is obtained of the amount of work that has been got through. Until the 4th August of last year hot a shovelful of earth had- | been turned, and now a railway, involving'a considerable extent of embankment has been formed between the quarries and the staging the length of rails laid being close upon a mile This railway rises from a flat a couple of feet above high-water mark to a level of 18ft the gradient being about 1 in 100, up which"the locomotive employed can without difficulty take 10 loaded waggons, each carrying three or four tons. Of the two quaries, that which is called the northern quarry, is worked by the prisoners, and consists wholly of basaltic rock interspersed with softer layers of volcanic clays. The men work under the surveillance of three or four of the warders, one of whom parades, rifle in hand outside a small sentry-box placed just opposite the face at which the prisoners are employed, l.he second quarry, near at hand, is worked by free labour, and 16 men are at present employed there. This rock is vf, ry similar to Port Chalmers stone, although it is not so crystaline or brittle. It is the stone commonly called volcanic breccia, There are two steam cranes at work m ™?f* quareies^Qne of five and one of seventon luting capacity, and a third (five-ton) will be available in a few weeks' time. Just at present stone is only being obtained from one quarry, as the prisoners are employed conveying debris and refuse from the northern quarry for the formation of a track across the low-lying flat between the works and the southern boundary ol the north spit. All the stone which has wifwt T* has been obtained by three large blasts only and a few smaller ones Immense quantities of rock have been dislodged at o?maW-' f nd *?, W° S°me idea o! ** "* wnZi X 1 av"W>le, One (3uim-y »lone-th,it Wadi y 6e labour-ca» send out about 500 Altogether, an inspection of the works gives a. very satisfactory impression as to the progress that lias been made, As already stated, not a ff&tlK pufc,to-the Br°M8 r°M imtil August ,'\fk 9> iif StaglnS was not commenced Wv «nt i t » more satisfactory still to know that the work is so far keepmg well mthin the engineers calculations, and that his total estimate (£86,000) may, if all goes well, be regarded as perfectly safp. S